THE UNITED REPUBLIC OF TANZANIA

PRESIDENT’S OFFICE, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

                                             NJOMBE REGION  

FORM SIX PRE-MOCK EXAMINATION

CODE: 132/2                                                                            CHEMISTRY 2

(For both school and private candidates)

TIME: 3:00 HRS                                          Friday, 22^nd August 2023 A.M  

INSTRUCTIONS

1.      This paper consists of six (06) questions.

2.      Answer only five (05) questions.

3.      Each question carries twenty (20) marks.

4.      Mathematical tables and non-programmable calculators may be used.

5.      Cellular phones and any unauthorized materials are not allowed in the examination room.

6.      Write your examination number on every page of your answer booklet(s)

7.      For calculations you may use the following constants

•      Universal gas constant, R=8.314JK^-mol^- or 0.0821K^-atm mol^-K^-dm³

•      Velocity of light, C=3.0 ×10⁸m/s

•      Standard temperature=273K

•      GMV=22.3dm³

•      1Faraday = 96500C

•      Standard pressure=760mmHg = 1.0 ×10⁵N/M² = 1 atm

01. (a)        (i) What does the term disprotonation means?

(ii) The reaction between dichromate (vi) Ions and chloride Ions in Acidic solution yield chlorine and chromium (iii) Ions as shown in the following unbalanced equation:

Cr2O7(aq) + Cl-(aq) → Cr3+(aq) + Cl2(g)

Derive the balanced Half – reaction equations and over all Net Equation for this redox reaction.

 (b)A Form five student was trying to balance the equation then he noticed that single      equation tends to loose and gain an electron simultaneously. State which of the following equation potray such behavior.

(i)   CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

(ii)    Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

(iii)  Cr2O72-(aq)  + 2OH-(aq) → 2CrO4 + H2O(l)

(iv)   O3(g) + NO(g) → O2(g) + NO2(g)

(c)  Identify the oxidizing agent, reducing agent, the substance being oxidized and the substance being reduced in 01 (b) (i-iv)

(d) Calculate the Emf of the following 

 Pb/Pb²⁺_aq(1×10⁺³m)// Cu²⁺ (1×10^-2m)/ Cu_(s)

Given the following standard reduction potentials     Pb²⁺/Pb E^θ= - 0.126v: al²⁺/ Cu, E^θ = 0.34v.

 02. (a)  (i) State the distribution law.

(ii) Distribution of solute particles in some given solvents can be governed by different condition and principles. Briefly explain the conditions that govern such distribution.

(b)   (i) Calculate the percentage by mass of bromo benzene (C₆H₅Br) in the distillate when a mixture of bromo benzene and water distills at 65˚C in the steam. The vapour pressure of bromo benzene and water are 1.59 × 10⁴ and 8.50 × 10⁴Nm^-2 respectively.

(ii) Heptane (C₇H₁₆) and Octane (C₈H₁₈) form an ideal solution at 373K, the vapour pressure of pure heptane and octave were 105.2Kpa and 46.8 Kpa respectively. Calculate the vapour pressure of the mixture of 26.0g of heptane and 35.0g of octane.

(c)  Compound P has a partition coefficient of 4.00 between the Ethoxyethane and water. Given that 2.0g of P is obtained in solution, in 50cm³ of water, calculate the mass of P that can be Extracted from the Aqueous solution by

(i)     50cm³ of Ethoxyethane

(ii)  Two successive extractions of 25cm³ of ethoxyethane each

(d)       To a solution containing 0.1m Cl^- and 0.01m CrO₄^2- a solution of AgNO₃ is added slowly.

(i)  Which salt will precipitate first between AgCl and AgCrO₄? Show clearly how you arrived to your answer.

(ii)  Find the concentration of the Ion that will precipitate first at the time the second Ion will start precipitating. 

Use Ksp (AgCl) = 2.72 × 10^-10 and Ksp (Ag₂CrO₄) = 2.4 × 10^-12

03.  (a) Rate of chemical reaction can proceed fast or slow depending on some factors in a given       chemical reaction. Briefly explain. (b)  consider the following reaction 

H2(g) + I2 (g) → 2HI(g)

       If the rate constant K at 310˚C and 420˚C is 1.3 × 10^-3dm^-3mol^-s^- and 6.3 × 10^-3dm     ³mol^-s^- respectively, what is the activation energy Ea for the reaction?

 (c) The reaction of nitric oxide with hydrogen at 1280˚c is given by the equation

 2NO₂ (g) + 2H_{2 (g)} → N₂ + 4H₂O

This reaction was studied and the following results were obtained

(i)       Determine the order with respect to each reactant and the overall order of the reaction

(ii)    Establish the rate law for the reaction

(iii)  Calculate the rate constant

03.  a) An aromatic compound D (C₈H₈O) give a positive result with 2.4 dinitro – phenyl      hydrozone but gives yellow precipitate of compound E treatment with iodine and      sodium solution. Compound D give negative Tollens or Fehling test. On drastic      oxidation with KMnO₄ forms a carboxylic acid F (C₇H₆O₂) which is also formed along      with the yellow compound in the above reaction. Identify the structure D, E, and F also       write all chemical reaction involved.

(b) A compound A of Molecular formula of C₃H₇O₂N On reaction with iron and      concentrated hydrochloric acid give the compound B of molecular formula C₃H₈O.      Compound C Gives Effervescence with sodium on oxidation with CrO₃ compound C      given saturated aldehyde containing three carbonic atoms deduce the structure of A, B       and C

04.  (a) (i) Generally extraction of metals from their ores involves four stages. Obtaining the    ore, concentating the ore, concentrating the compound of interest in the ore, chemical            reduction and refining of the crude metal.  Describe how Aluminium is extracted   from its ore basing on these stages.

 (ii) Show that the properties of aluinium suit its wide range use. 

 (b)  Transitional elements show a variety of behaviours. With vivid example explain five      (05) properties shown by such metals.

 (c)  Give the IUPAC name of the following

i.   [Cr(H₂O)₄(NH₃)₂]Cl₃

ii.  [CoCl(NO₂) (en)₂]⁺

iii.  K₄[Fe(CN)₆]

iv.  [FeBr₂(H₂O)₄]⁺

v.   [CoCl₂(NH₃)₄]₃ [Cr(CN)₆]

05.  (a) (i) Arrange the following compound in the order of increasing acidic strength  Phenol, phenylmethanol, 2-nitrobenzoic acid, benzoic acid

 (ii) A compound with the following structural formula was extracted from certain yellow flowers H₂N-CO-H₂CHOH-CO-OH.

 From your knowledge in organic chemistry give the product that will be formed   when this compound is treated with 

  i)Nitrous acid (ii) Ethanol (iii) LiAlH₄     (iv) Potassium dichromate      (v) PCl₅

(b)  Show the initiation step and propagation step for the following Polymerization types for Polytetrafluoroethene (PTFE) polymer.

i.   Free radical polymerization

ii.   Cation polymerization

iii. An ionic polymerization

(c) Write the monomers forming the following polymers and show the polymerization method        used

i.   PVC

ii.  Bakelite

iii. Teflon 

iv.  Nylon bile

v. Dacron

THE UNITED REPUBLIC OF TANZANIA

PRESIDENT’S OFFICE, REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

                                         NJOMBE REGION  

FORM SIX PRE-MOCK EXAMINATION

CODE: 132/1                                                                       CHEMISTRY 1

TIME: 3:00 HRS                                              Friday, 18^th August 2023 A.M  

INSTRUCTIONS

1.      This paper consists of section A and B with a total of ten (10) questions

2.      Answer ALL questions in section A and two questions from section B.

3.      Mathematical tables and non-programmable calculators may be used.

4.      Cellular phones and any unauthorized materials are not allowed in the examination room.

5.      Write your examination number on every page of your answer booklet(s) 6. The following information may be used.

a)        Universal gas constant, R=8.314JK^-1mol^-1 or 0.0821 atmdm³mol^-1

b)       Rydberg constant R_H=1.09678 x 10⁷m^-1

c)        Standard pressure =760mmHg =1.0X10^-5Nm²

d)       A mass of electron =9.11x10^-31kg

e)        Density of water =1g/cm³

f)        Velocity of light, C= 3.0 X 10⁸ m/s

g)       Avogadro’s number = 6.02x10²³

h)       Planks constant, h=6.63 x 10^-34Js

i)         Atomic masses

H=1, C=12, O=16, N=14, Cl= 35.5, Br=80, Na=23

SECTION A (70 MARKS)

Answer all questions from this section.

1. (a)Why does hydrogen spectrum have large number of lines despite the fact that hydrogen has one electron?                                                       (02 marks)

(b)   Calculate the wavelength of an alpha particle having a mass of 6.7 x 10^-25 kg   moving with a speed of 1000m/s.                                     (04 marks)

(c)   Naijongoro a chemistry teacher at Muungano secondary school told his student that “Dalton atomic theory is primitive” supports Mr. Naijongoro using four points.                                                                                    (04 marks)

2. (a) Write down the molecules or ions that undergo the following hybridization scheme;

 i. sp³d 

ii. sp³d²

iii. sp³                                                                                                  (03 marks)

(b)  CO₂ is a non- polar molecule while H₂O is polar molecule. Explain.  (03 marks)

(c)   Makene a form five student was arguing that double bond is a weaker than single bond because double bond has a weak Pi bond. But Anna happened to educate Makene that in double bond there are two bonds, a strong sigma bond and weak pi bond while in single bond there is only one bond, which is strong sigma bond. Using four points justify that sigma bond is different from Pi bond                                                                                                (04 marks)

3.      (a) Define the following 

i. Ebullioscopic constant 

ii. Van’t Hoff’s factor

iii. Colligative properties                                                             (03 marks) 

(b)The vapour pressure of water at 50⁰C is 92.5mmHg. At the same temperature a solution containing 9.14g of urea in 150g of water has a vapour pressure of 90.8mmHg. Determine the molecular mass of urea.                                (04 marks)

(c) What is the boiling point of a solution made by dissolving 45.0g of NaCl in 500g of water (ebulliscopic constant, K_b=0.512)                            (04 marks)

4.      (a) Explain the following.

i.        Heat of neutralization

ii.      Heat of solution                                                                   (02 marks)

(b) 1. 5g of ammonium nitrate was added to 35.0g of water in a plastic beaker and stirred until the salt dissolved. The temperature of the solution dropped from 22.7⁰C to 19.4⁰C basing on the given information respond to the following questions.

i.        Is the process endothermic or exothermic? Explain

ii.      Calculate the heat of solution ammonium nitrate in KJ/mol given that specific heat capacity of water=4.184J/g⁰C and density of water is =1g/ml                                                                                              (04 marks)

(C) Calculate the heat of formation of ethyl alcohol (C₂H₅OH) if the heat of combustion of ethyl alcohol is -1380.7KJ/mol and heat of formation of CO₂ and H₂O are 393.9KJ/mol and -286KJ/mol respectively.                        (04 Marks)

5.    (a) Aluminium oxide is said to be amphoteric. Explain this fact by aid of chemical Equation.                                                                             (03 marks)

(b)Iron III carbonate never exists. Explain this statement.    (01 marks)

(c)Explain the following with the aid of chemical reaction if applicable.

i.        MgCl₂.6H₂O when heated can never give out unhydrous MgCl₂

ii.      CuCl₂ solution is acidic to litmus paper

iii.    Fe₃O₄ is called mixed oxide.                                                            (06 marks)

6. (a) Explain these concept

i.        Dynamic equilibrium 

ii.      Irreversible reactions                                                             (03 marks) 

(b) At 773K, the reaction between gaseous nitrogen and hydrogen to form ammonia gas has a K_C =6.0 x10^-2dm⁶mol^-2. Compute the value of K_P for this reaction.                                                                                        (03 marks)

(c) A mixture of CO and steam consisting of 0.25mol each constituent is placed in 500ml flask and the mixture heated up to 900K. The reaction equations is 

CO (g)+H2O(g)     →  H2(g)+ CO2( g). 

What is the composition of the equilibrium mixture if the K_C for this reaction is 1.56?                                                                                                      (04 marks)

7.      (a)Suppose you are invited by a village chairman Mzee Yakwamba at Igongolo village to educate people about the importance of ozone layer in the atmosphere. Briefly explain with the aid of equations where necessary on the formation of ozone layer, primary causes of ozone layer destruction and three effects of ozone layer depletion.  (08 marks)

(b)How can an elemental sulphur be efficiently converted to sulphuric acid in the soil?                                                                                               (02 marks) 

SECTION B (30 MARKS)

Answer two (02) questions in this section. 

8.      (a) (i) By using the chemical equation explain why tertiary haloalkane can not   undergo S_N2 reaction mechanism

 (ii) Benzene is more reactive than nitrobenzene while methylbenzene is more  reactive than benzene. Explain this observation.                                 (04 marks)

(b) Explain  which substituent    entered     in  the       benzene   ring   first

               (03 marks)

(c)             Convert CH₃CH₃ to in more than three steps. (03 marks)

(d)            From the scheme below identify the molecules V, W, X, Y, and Z

(05 marks)

9.      (a) Explain briefly the physical significance of the van der waals’ parameters, “a” and” b”                                                                                                (02 marks)

(b) Explain the following.

i.    Aerated water bottles are kept under water during summer

ii.  The size of weather balloon becomes larger and larger as it ascends into high attitudes.                  (03 marks)

(c)  Explain briefly the application of Avogadro’s law in life situations. (03 marks)

(d)   A hydrocarbon contains 10.5g of carbon per g of hydrogen. 1 litre vapour of hydrocarbon at 127^oC and 1atm pressure weighs 2.8g. Find the molecular formula of a hydrocarbon.  (07 marks) 

10.  Predict the major product(s) for each of the following reactions

(b) When 1,2-dibromodecane was treated with potassium hydroxide in aqueous ethanol, it yields a mixture of three isomeric compounds of molecular formula C10H19Br. Each of these compounds was converted to dec-1-yne on reaction with sodium amide in dim ethyl sulphoxide. Identify the three compounds. (06 marks)

(c) Explain briefly the preparation of acetylene (ethyne) by; -

i. Pyrolysis of natural gas. ii. Action of water on calcium carbide. (04 marks)

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

KILIMANJARO REGIONAL COMMISSIONER’S OFFICE

FORM SIX MOCK EXAMINATION

CHEMISTRY 2

INSTRUCTIONS 

1.                This paper consists of six (06) questions
2.                Answer any five (05) questions.
3.                Each question carries twenty (20) marks.
4.                Mathematical table and non-programmable calculator may be used.
5.                Write your Examination Number on every page of your answer booklet(s)
6.                Cellular phones are not allowed in the examination room.
7.                For calculations you may use the  following constants:

•                  Atomic masses: K=39, Ag=108, Br=80, Cl=35.5, Na=23, S=32, Ca=40, Ar = 40, Fe=56
•                  Atomic number: Al=13, O=8, Li=3, Cl=17, K=19, Cr=24, Cu=29, Fe=26,

Ca=20, Ag=47, Ne=10, Ar=18, Kr=36, Xe=54, Br=35, Mg=12, F=9, N=7

•                  Gas constant, R=0.0821 atmLmol^-1K^-1 or 8.314JMol^-1K^-1.

1.                (a)State partition law

(b) 25cm³ of 0.2 mol dm³ solution of copper (II) sulphate were mixed with 25cm³ of 1 mol dm^-3 ammonia solution. When these solutions mix, a royal blue solution is made. This contains a complex ion, which we can write as Cu(NH₃)_x²⁺.The total 50cm³ of the solution were shaken with 50cm³ of trichloromethane. After giving time for equilibrium to be achieved, the two solutions were separated. The ammonia was extracted from the trichloromethane. After performing a titration it was found that 0.2 x 10^-3 mol of ammonia was present in the trichloromethane. Taking the partition coefficient for ammonia between water and trichloromethane as 25.

1. Calculate the number of moles of free ammonia in the orginal 50cm³ of the royal blue solution
2. What is the total number of moles of ammonia in the trichloromethane and the 50cm³ of the royal blue solution?
3. How many moles of ammonia were present before the complex ion was made?
4. How many moles of ammonia had been used in joining with the copper (ii) ions?
5. How many moles of copper (II) sulphate had been used
6. Given that every 1mol of copper (II) sulphate contains 1 mol of copper (II) ions, how many moles of coper (II) ions had been taken?
7. What is the ratio of moles of copper (II) ions to moles of ammonia molecules in the complex ion?
8. What is the formula of the complex ion?

(c)(i)State Raoult’s law of vapour pressure

(ii)Benzene (C₆H₆) and toluene form a nearly ideal solution. At 313K the vapour pressure of pure benzene is 150mmHg and of pure toluene is 50mmHg. Calculate the vapour pressure of a mixture of these two liquids containing equal masses at the given temperature.

(d)A. 1.0g sample of Fe₂O₃ solid of 55.2 per cent purity is dissolved in acid and reduced by heating the solution with zinc dust. The resultant solution is cooled and made up to 100cm³. An aliquot of 25.0cm³ of this solution requires 17.0cm³ of 0.0167M solution of an oxidant for titration. Calculate the number of electrons taken up by the oxidant in the reaction of the above titration. 

2.                (a)Distinguish between the following terms:

1. Rate constant and rate law
2. Elementary step and rate-determining step
3. Molecularity and order of reaction

(b)The following results were obtained for the decomposition of nitrogen (v) 

Oxide. 2N₂O_5(g) → 4NO_2(g) + O_2(g)

1. What is the Order of reaction?
2. Determine the rate constant for the reaction
3. What is the initial rate of reaction when the concentration of N₂O₅ is 2.4 x 10^-2 moldm^-3?

(c)(i)The rate constant of a first order reaction becomes 5 times when the temperature is raised from 350K to 400K. Calculate the activation energy for the reaction.

(ii)During the nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If lug of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically?

(d)The decomposition of a certain insecticide in water follows first order kinetics with a rate constant of 1.45 year^- at 285K. A certain amount of this insecticide is washed into a lake on June 1^st leading to a concentration of 5.0 x 10^-7gcm^-3. Assume that the average temperature of the lake is 285K.

1. Calculate the concentration of the insecticide on June 1^st of the next year.
2. How long will it take for the concentration of the insecticide to drop to 3.0 x 10^-7 gcm^-3?

(e)Iodide reduce iron (III) to iron (II) according to the reaction;

2Fe³⁺_(aq) +2I^-_(aq) → 2Fe²⁺_(aq) + I_2(aq)

Experimentally, it was found that doubling the concentration of Fe³⁺, ions, doubled the rate of reaction. On the other hand, doubling the concentration of iodide ions increased the rate of the reaction by a factor of 4. Determine the order of reaction with respect to each reactant, the overall order and write the rate law of the reaction.

3.                (a)(i)Give any three (3) applications of common ion effect

(ii)The solubility of Pb(OH)₂ in water is 6.7 x 10^-6. Calculate the solubility of Pb(OH)₂ in a buffer solution of Ph=8

(b)Hair bleaching solutions contain hydrogen peroxide, H₂O₂. The amount of hydrogen peroxide in the solution can be determined by making H₂O₂₊ react with an acidic solution of potassium dichromate. The unbalanced equation for the reaction is;

H₂O_2(aq) + Cr₂O₇^2-_(aq) + H⁺_(aq) → O_2(g) + Cr³⁺_(aq) + H₂O

A.30.00g sample of the bleach solution needed 75.8ml of 0.388MK₂Cr₂O₇ to react completely with the bleach. Assuming no other compounds that react with K₂Cr₂O₇ are in the solution, what is the mass percent of H₂O₂ in the bleach?

(c)For the titration of 75.00ml of 0.1M acetic acid with 0.1M NaOH, calculate the pH;

1. Before the addition of any NaOH solution,
2. After 25.00Ml of the base has been added,
3. After half of the HC₂H₃O₂ has been neutralized, and
4. At the equivalent point

(d)When edta(ethylenediaminetetraacetic acid) is titrated against calcium salts, experiments show that one mole of edta reacts with one mole of Ca²⁺. This technique is used in clinical analysis to estimate the concentration of calcium in blood serum. Concentration between 7 and 13mg of calcium per 100cm³ of blood serum are normal.

One cubic centimeter of blood serum was taken from a patient and found to require 2.75cm³ of 0.0015M edta solution.

1. Calcium the concentration of calcium in the patient’s blood.
2. Is there an abnormal level of calcium concentration in the patient’s blood?

4.                (a)Consider the following ions; Cl^-, K⁺, S^2-, Sc³⁺ and Ca²⁺

Arrange them in order of;

1. Increasing ionic size
2. Increasing polarizing power
3. Increasing polarisability

(b)Observe the isomers [Co(NH₃)₅Br] SO₄ and [Co (NH₃)₅SO₄] Br, then answer the questions that follows:

1. Name the isomers
2. What ions will the isomers yield in solution?
3. Give two chemical tests that would be used to distinguish between the isomers
4. What is the oxidation state and coordination number of cobalt in the complexes?

(c)50cm³ of a solution of 0.1M[Co(NH₃)₅Br]SO₄ was mixed with 50cm³ of a solution of 0.1MKBr and the solution was made up to 200cm³. What is the concentration of Br in this solution? (Assume the two compounds ionize completely and supply two ions in solution)

(d) Explain the following observations;

1. Lithium salts have a greater degree of covalent character than the other halides of the group.
2. Li⁺ is far smaller than the metal ions but it moves through a solution less rapidly than the others.
3. It is not possible to prepare hydrogen iodide by the action of concentrated sulphuric acid on potassium iodide
4. AlCl₃. 6H₂O is acidic in aqueous solution while CH₃COONa is basic in aqueous solution
5. When Sulphur dioxide is bubbled through an acidified aqueous solution of K₂Cr₂O₇, the yellow colour of the latter turns green.

5.                (a)Identify compounds A, B, C, D and reagents X, Y and Z in the following scheme of reactions

(b)Given the structure of compound K

Write down the chemical equation for the reaction between compound K and 

1. Bromine water
2. feCl₃
3. Explain whether the compound will give iodoform test. If it gives positive iodofrm test, what are the reagents and condition for the test?

(c) The following experiment was carried out by a form six student.

A 9.2g sample of ethanol and 20.4g of 2-methylbutanoic acid were mixed in a flask and 2.0g of concentrated sulphuric acid was added. The mixture was refluxed for four hours and then fractionally distilled to give 17.4g of the crude ester. The ester was washed repeatedly with aqueous sodium carbonate until there was no more effervescence. After further washing with distilled water and drying, 15.6g of pure ester were obtained.

By referring to the experimental procedure above,

1. Explain why the crude ester was washed repeatedly with aqueous sodium carbonate.
2. State which gas was responsible for the effervesce
3. Calculate how many moles of each reactant were reacted.
4. Use your answer in (c)(iii) to calculate the percentage yield of pure ester obtained in the above experiment.

(d)Suggest the simple chemical test that would be used to distinguish the following compounds:

1. Ethanol and acetone (Propanone)
2. Ethanamine and N-methylethanamine

6.                (a)Name the following compounds according to the IUPAC system;

(b)An organic compound A(C₅H₁₀O) containing carbonyl group was reduced with Li[AlH₄] to give compound B.B was dehydrated with concentrated sulphuric acid to give product C of molecular formula C₅H₆O. D gives positive iodoform reaction.

1. Identify A, B, C and D compounds. Give their structural formula and IUPAC names.
2. Give equations for all reaction

(c)Show how the following concersion may be achieved:

(d)Nylon 6-6 has a structure containing the following repeat unit;

[CO-(CH₂)4-CONH-(CH₂)₆-NH]-

1. Give the structures of the monomers from which this polymer could be made.
2. What-type of polymer is this?

(e)Write the polymer section unit of 

1. Polystyrene
2. Dacron
3. Protein

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

KILIMANJARO REGIONAL COMMISSIONER’S OFFICE

FORM SIX MOCK EXAMINATION

CHEMISTRY 1

INSTRUCTIONS 

1.   This paper consists of ten (10) questions in sections A, and B
2.   Answer all questions in section A and choose any two (2) questions from section B.
3.   Each question carries ten (10) marks in section A and fifteen (15) marks in section B
4.   Cellular phones and any other unauthorized materials are not allowed in the examination room
5.   Write your Examination Number on every page of your answer booklet(s)
6.   The following constant may be used.

•      Gas constant, R=0.0821 atmLmol^-1K^-1 or 8.314JMol^-1K^-1,
•      Rydberg’s constant, RH = atmLmol^-1K^-1 or 8.314JMol^-1K^-1,
•      Velocity of light, c=3 x 10⁸m/s
•      Planck’s constant, h= 6.63 x 10^-34Js
•      Atomic masses: H= 1, C=12, N=14. O=16, P=31, Br=80

SECTION A (70 Marks)

Answer all questions in this section

1.   (a)Earlier we met the idea that the probability of finding the electron at any particular points is zero. We also spoke about the probability of finding the electron at a given distance from the nucleus. Try to explain why these two ideas are not contradictions of one another.

(b)Werner Heisenberg derived a remarkable result using a different (but compatible) theory to that of Schrodinger. He said that it was impossible to measure with complete accuracy both the position and momentum of an electron. This statement has come to be known as Heisenberg’s uncertainty principle. We can write the uncertainty in position x and momentum as p. Heisenberg’s equation is; 

1.          If the position of an electron is known to within 10^-12m, what is the uncertainty in its momentum?
2.          In our large-scale world, is there a limit (in principle) on the accuracy with which we can measure the momentum and position of a particle, e.g. a golf ball?
3.          Guess the effective value of Planck’s constant in the large-scale world.

(c)Why do the spacing between lines in hydrogen spectrum decreases as one goes away from the nucleus?

(d)An electron moves from n= 5 to a lower energy level in visible part of electromagnetic spectrum. Calculate:

1.          Energy possessed by electron in the new energy level (shell)
2.          Energy emitted during transition from n=5 to a lower energy level
3.          Frequency of radiation emitted.

2.   (a)Write short notes on the following;

1.          Hydrogen bonding
2.          Van der Waal forces

(b) Explain the following observations:

1.          AlCl₃ is covalent while AlF₃ is ionic.
2.          CO₂ is non-polar molecule while SO₂ is polar

(c)Using VSEPR theory, predict the molecular geometry and the type of hybridization in which the following molecules undergo;

(i) H₂O  (ii) SO₃ (iii) CS₂ (iv) SO₄^2-

3.   (a)A bromide of phosphorus is found to diffuse in the gaseous state more slowly by a factor of 3.923 than nitrogen gas under the same conditions.

1.          Calculate the relative molecular mass of the bromide
2.          Given that bromide molecule contains one atom of phosphorus, write down its formulate

4.   (a)Explain the following

1.          Why is the osmotic pressure measurement preferred for determining molecular mass of protein?
2.          Why the equimolar solutions of sodium chloride and glucose are not isotonic?

(b)Arrange the following solutions in order of increasing of their boiling points;

0.1MKCl, 0.01M glucose, 0.01M MgCl₂, 0.01MKCl.

(c)A 0.004kg of acetic acid (CH₃COOH) is added to 500cm³ of water. If 25% of the acid is dissociated, what will be the depression in freezing point?

(K_f for water = 1.86° Ckg/Mol, density of water = 0.997/cm³).

5.   (a)With examples state the following;

1.          Basic oxides
2.          Acidic oxides
3.          Amphoteric oxides

(b)You are given a list of metal carbonates in the below. Tabulate your results by using (V) to indicate soluble carbonate and (X) for insoluble carbonate in the space provided.

(c)Using a balanced chemical equation, describe the decomposition of the following compounds when heated.

1.          Sodium carbonate (Na₂CO₃₎
2.          Hydrated crystals of aluminium chloride (AlCl₃.6H₂O_(s))
3.          Anhydrous copper (II) sulphate (CuSO_4(s))
4.          Sodium hydrogen carbonate (NaHCO_3(s))

6.   (a)State and give examples for each of the following terms;

1.          Physical equilibrium
2.          Chemical equilibrium

(b)1dm³of dinitrogen tetraoxide, N₂O₄ weighs 2.5g at 60°C and 1 atm pressure. Find;

1.          The degree of dissociation of N₂O₄ into NO₂
2.          The value of Kp

(c)When a yellow solution of iron (III) chloride, FeCl₃ and a colourless solution of potassium thiocyanate, KSCN were mixed in a test tube, a red colour appeared and the following equilibrium was established;

Fe³⁺_(aq) + SCN_(aq)  [Fe(SCN)]²⁺_(aq)

Yellow    Red

1.          What is the effect on the Fe³⁺ ion concentration up adding KSCN to the equilibrium mixture?
2.          Why has a change in pressure no effect on equilibrium?
3.          The red colour faded when the test tube containing the equilibrium mixture was placed in an ice-water bath. State whether the value of Kc for this reaction is high or low at the lower temperature. Is the forward reaction exothermic or endothermic? Justify your answer.

7.   (a)(i)State Hess’s law of constant heat summation.

(ii)Use Hess’s law to calculate the enthalpy change in the hypothetical reaction 

2MgCl_(s) → Mg(s) + MgCl_2(s). If the standard enthalpy of formation of MgCl is -130kJ/mol and the standard enthalpy of formation of MgCl₂ is -640kJ/mol.

(b)The table below lists a number of some mean bond enthalpies, 

1.          Given that the enthalpy of combustion to form carbon dioxide and steam is

-2102Kj/mol for propane and -1977Kj/mol for propene. Determine the enthalpy for the oxidation of 1 mole of propane to propene and steam.

C₃H₈(g) + ½O_2(g) → C₃H_6(g) + H₂O_(g)

2.          Use the mean bond enthalpies in the table above together with your answer in ((i) above to calculate the bond enthalpy of the O=O bond in the oxygen molecule.

(c)Calculate the heat of formation of anhydrous sodium chloride from;

2Na_(s) + 2H₂O_(l) + → 2NaOHaq + H_2(g) + H_2(g) H=-87.0 kcals

H_2(g) + Cl_2(g) + aq. 2HClaq → H=-78.60kcals

NaOHaq. + HClaq → NaClaq. + H₂O_(i)H=-13.70kcals

NaCl_(s) + aq.NaClaq. → H=+1.20 kcals

2H_2(g) + O_2(g)2H₂O_(l) →H=-136.0kcals 

SECTION B (30 Marks)

Answer any two (2) questions from this section

8.   (a)Give the IUPAC names of the following compounds;

(b)When 20cm³ of a gaseous of a gaseous hydrocarbon A, are exploded with 150cm³ of oxygen, the residual gases occupied 110cm³. After shaking the residual gases with aqueous sodium hydroxide, the final volume was 30cm³ (all volumes were measured at the same temperature and pressure. What is the molecular formula of A.

(c)Outline how the following conversions can be achieved in not more than three steps.

1.          CH₃CH₂Cl → CH₃CH₂ – CH –CH₂

      |    |

      Cl Cl

2.          CH₃CH₂CH₃ → CH₃CHCH₃

|

Br

(d) What mass of propene is obtained is from 34.0g of 1-iodopropane on heating with ethanoic KOH, if the yield is 36%

9.   (a)How does straight fertilizer differs from complete fertilizer. Give one example in each case.

(b)Give the name of the fertilizer whether is straight, mixed or complete fertilizer and the type of the nutrients which contain in the following fertilizer coding below:

(i) 10:20:15   (ii) 40:0:0  (iii) 40:8:0

(c)The soil of Mawenzi farm contains the following nutrients where all the values are given inmeq per 100g of oven dry soil: Ca²⁺=35, Mg²⁺=20, Na⁺= 4, H⁺=7, Al³⁺=10.

Calculate;

1.          Cation exchange capacity
2.          Percentage base saturation
3.          The quantity of Mg²⁺ in grams present in 100g of the dry soil

(d)A farm required 240kg of nitrogen. What weight of urea fertilizer coded 40:0:0 a farmer needs to add to his/her farm to meet the demand? Show clearly how you obtain your answer.

10. (a)Primary alkyl halide A C₄H₉Br reacted with alcoholic KOH to give compound B. Compound B is reacted with HBr to give C which is an isomer of A. When C was reacted with sodium metal it give a compound D C₈H₁₈ that was different than the compound when n-butyl bromide was reacted with sodium with sodium. Give the structural formula of Compounds A to D

(b)Suggest suitable tests to distinguish the following compounds.

1.          Cyclopentane and Pent-2 ene
2.          Cyclopentanol and phenol

(c)Briefly explain why (CH₃)₃C-Cl reacts by S_Nl mechanism while CH₃CH₂CH₂-Cl reacts by S_N2 mechanism

(d)How does benzene react with the following?

1.          Chloroethane in the presence of AlCl₃
2.          Chlorine in the presence of FeCl₃
3.          Carbon monoxide in the presence of AlCl₃
4.          Concentrated sulphuric acid and heat
5.          Chloroform in the presence of AlCl₃

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE

(MTWARA AND LINDI)

132/3B CHEMISTRY 3B

(For Both School and Private Candidates)

(ACTUAL PRACTICAL B)

TIME: 3:20 HOURS Friday, 11^thFebruary, 2022 a.m.

Instructions

1.    This paper consists of Three (3) questions.

2.    Answer all questions.

3.    Question one (1) caries (20 marks), questions two (2) and three (3) each caries (15 marks).

4.    Mathematical tables and Non programmable calculator may be used.

5.    Write your Examination Number on every page of your answer booklet(s).

6.    For your calculations the following constants may be useful:

H=1, C=12, O=16, Cl=35.5, S=32, Na=23, Cu=64, K=39, Fe=56.

Universal gas constant, R=0.0821 Atm dm³mol⁻¹K⁻¹ or 8.314Jmol⁻¹K⁻¹

GMV= 22.4dm³

Specific heat capacity of solution= 4.2Jg⁻¹K⁻¹

Density of solution= 1g/cm³

1. You are provided with the following:

X: A solution containing a mixture of sodium carbonate and sodium hydroxide in aqueous solution

Y: A solution containing 9.125g of pure hydrochloric acid in 0.25dm³ of equations solution.

Methyl orange indicator

Phenolphthalein indicator

Theory:

Reaction of hydrochloric acid with both sodium carbonate and sodium hydroxide can be represented by the following equations:

NaOH+HCl →NaCl+H₂O

Na₂CO₃+HCl →NaHCO₃+NaCl

NaHCO₃+HCl →NaCl+H₂O+CO₂

Procedures:

(i)         Pipette 20cm³ or 25cm³ of solution X into a conical flask.

(ii)         Add two or three drops of P.O.P.

(iii)        Titrate this solution against solution Y until color change is observed.

(iv)        Record the first titre value.

(v)         Add two drops of M.O to the same solution.

(vi)       Continue to titrate until a second color change is observed.

(vii)       Record the second titre value.

(viii)      Repeat your titration procedure (i) to (vii) above two times and record your results as shown here below.

Results:

 The volume of the pipette used was cm³

Burette readings

Table 1

Summary:

.............cm³ of solution X required..... cm³ of Y when POP was the indicator .............cm³ when MO was the indicator.

Questions:

 (b)    Indicate the chemical equations which were appropriate to the titre value found when using.

(i)        P.O.P

(ii)     M.O

(c)     Calculate the concentration of.

(i)        Sodium hydroxide in mol/dm³ in solution X

(ii)     Sodium carbonate in mol/dm³ in solution X

(d)    Calculate the percentage composition by mass of both sodium hydroxide and sodium carbonate in solution X.

You are provided with the following:

X₁: 2g of NaOH pellets.

X₂: 1M sodium hydroxide solution. X₃: 1M Hydrochloric acid solution.

X₄: Distilled water.

Procedures 1:

(i) Measure 50cm³ of X₄ in 100cm³ plastic beaker or any 100cm³ plastic container.

 (ii) using thermometer to measure the initial temperature of water, T₁ =  .

(iii)      Take 2g of sodium hydroxide pellets and dissolve in 50cm³ water in a plastic beaker stir the solution and make sure all the solute dissolve. Record the final temperature of solution when no further temperature change.

(iv)      Tabulate the results as follows:

Procedures 2:

(i)           Measure 50cm³ of X₂ and put in 100cm³ plastic beaker. Record the initial temperature, T₁

(ii)        Measure 50cm³ of X₃ in measuring cylinder and measure its initial temperature, T₂ while in measuring cylinder.

(iii)      Pour X₃ solution from measuring cylinder to plastic beaker containing X₂, stir well to mix then measure the final temperature attained using the thermometer.

(iv)      Tabulate the results as follows:

Questions:

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE (MTWARA AND LINDI)

132/3A CHEMISTRY 3A

(For Both School and Private Candidates)

(ACTUAL PRACTICAL A)

TIME: 3:20 HOURS                                                                    Tuesday, 08^th February, 2022 a.m.

Instructions

1.    This paper consists of Three (3) questions.

2.    Answer all questions.

3.    Question one (1) caries (20 marks), questions two (2) and three (3) each caries (15 marks).

4.    Mathematical tables and Non programable calculator may be used.

5.    Write your Examination Number on every page of your answer booklet(s).

6.    For your calculations the following constants may be useful:

H=1, C=12, O=16, Cl=35.5, S=32, Na=23, Cu=64, K=39, Fe=56.

Universal gas constant, R=0.0821 Atm dm³mol⁻¹K⁻¹ or 8.314Jmol⁻¹K⁻¹

GMV= 22.4dm³

Specific heat capacity of solution= 4.2Jg⁻¹K⁻¹

Density of solution= 1g/cm³

1.    You are provided with the following:

X: A solution made by dissolving 0.79g of KMnO₄ in 250cm³ of solution

Y: A solution made by dissolving 13.90g of FeSO₄.XH₂O in 500cm³ of aqueous solution acidified with sulphuric acid..

Z: A dilute sulphuric acid Procedures:

(i)           Put X in the burette.

(ii)        Pipette 20 or 25cm³ of Y into conical flask. Add 20cm³ of Z to the same conical flask.

(iii)      Titrate the solution in conical flask against X in the burette until permanent pink colour just appear. Record the burette reading.

(iv)      Repeat procedure (i) to (iii) three times and tabulate your results as shown below.

Results:

The volume of the pipette used was......................cm³

The volume of the burette used was .......................cm³

Burette readings

Summary:

.............................. cm³ of Y required ................. cm³ of X for complete reaction.

Questions:

(a)      (i) Write the redox half reactions for this titration.

(ii)        Write the overall balanced ionic redox reaction.

(iii)      Indicate the species which is oxidant and the one which is reductant.

(b)     Explain why an indicator is not used in this kind of experiment.

(c)      Explain why sulphuric acid and not hydrochloric acid is used in a particular experiment.

(d)     Calculate:

(i)    Concentration of FeSO₄.XH₂O in g/dm³

(ii)Concentration of KMnO₄ in g/dm³

(iii)   Molarity of KMnO₄

(iv)    Molarity of FeSO₄

(v)  Molar mass of FeSO₄.XH₂O (vi) Value of X in the formula FeSO₄.XH₂O

2.    You are provided with the following:

K: 4g of hydrated sodium carbonate (Na₂CO₃.10H₂O)

J: 2g of anhydrous sodium carbonate Na₂CO₃

Thermometer, small plastic beaker and distilled water.

Procedures:

(i)  Measure 50cm³ of distilled water and put in small plastic beaker. Record the initial temperature, T₁ = .

(ii)  Dissolve 4g of Na₂CO₃.10H₂O in the small plastic beaker contain water while stirring record the final temperature of solution, T₂ = ................

(iii)  Discard the contents in the plastic beaker and wash it then measure 50cm³ of distilled water and put in the plastic beaker. As usual take the initial temperature of water using the thermometer, T₃ = ..............

(iv)  Take 2g of anhydrous sodium carbonate, dissolve in plastic beaker containing distilled water, while stirring record the final temperature, T₄ = ...................

Results:

Questions:

(i)       Calculate the heat change in each experiment.

(ii)      Calculate the molar heat change in each experiment.

(iii)      Calculate the heat of hydration of anhydrous sodium carbonate to hydrated sodium carbonate

(iv) Comment on the different in the molar heat change of solution for salt K and

L

3.    Sample Q contains a two cations and two anions. Use the information given in the experiment column to complete the observations and inferences and hence identify the two cations and the two anions

Calculation

(a)       The cations in sample Q are           .

(b)     The anions in sample Q are

(c)      Sample Q is a mixture of

(d)     Give one application of cation obtained in life.

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE

(MTWARA AND LINDI)

132/3B CHEMISTRY 3B

(For Both School and Private Candidates)

(ACTUAL PRACTICAL B)

TIME: 3:20 HOURS Friday, 11^thFebruary, 2022 a.m.

Instructions

1.    This paper consists of Three (3) questions.

2.    Answer all questions.

3.    Question one (1) caries (20 marks), questions two (2) and three (3) each caries (15 marks).

4.    Mathematical tables and Non programmable calculator may be used.

5.    Write your Examination Number on every page of your answer booklet(s).

6.    For your calculations the following constants may be useful:

H=1, C=12, O=16, Cl=35.5, S=32, Na=23, Cu=64, K=39, Fe=56.

Universal gas constant, R=0.0821 Atm dm³mol⁻¹K⁻¹ or 8.314Jmol⁻¹K⁻¹

GMV= 22.4dm³

Specific heat capacity of solution= 4.2Jg⁻¹K⁻¹

Density of solution= 1g/cm³

1. You are provided with the following:

X: A solution containing a mixture of sodium carbonate and sodium hydroxide in aqueous solution

Y: A solution containing 9.125g of pure hydrochloric acid in 0.25dm³ of equations solution.

Methyl orange indicator

Phenolphthalein indicator

Theory:

Reaction of hydrochloric acid with both sodium carbonate and sodium hydroxide can be represented by the following equations:

NaOH+HCl →NaCl+H₂O

Na₂CO₃+HCl →NaHCO₃+NaCl

NaHCO₃+HCl →NaCl+H₂O+CO₂

Procedures:

(i)         Pipette 20cm³ or 25cm³ of solution X into a conical flask.

(ii)         Add two or three drops of P.O.P.

(iii)        Titrate this solution against solution Y until color change is observed.

(iv)        Record the first titre value.

(v)         Add two drops of M.O to the same solution.

(vi)       Continue to titrate until a second color change is observed.

(vii)       Record the second titre value.

(viii)      Repeat your titration procedure (i) to (vii) above two times and record your results as shown here below.

Results:

 The volume of the pipette used was cm³

Burette readings

Summary:

.............cm³ of solution X required..... cm³ of Y when POP was the indicator .............cm³ when MO was the indicator.

Questions:

 (b)    Indicate the chemical equations which were appropriate to the titre value found when using.

(i)        P.O.P

(ii)     M.O

(c)     Calculate the concentration of.

(i)        Sodium hydroxide in mol/dm³ in solution X

(ii)     Sodium carbonate in mol/dm³ in solution X

(d)    Calculate the percentage composition by mass of both sodium hydroxide and sodium carbonate in solution X.

You are provided with the following:

X₁: 2g of NaOH pellets.

X₂: 1M sodium hydroxide solution. X₃: 1M Hydrochloric acid solution.

X₄: Distilled water.

Procedures 1:

(i) Measure 50cm³ of X₄ in 100cm³ plastic beaker or any 100cm³ plastic container.

 (ii) using thermometer to measure the initial temperature of water, T₁ =  .

(iii)      Take 2g of sodium hydroxide pellets and dissolve in 50cm³ water in a plastic beaker stir the solution and make sure all the solute dissolve. Record the final temperature of solution when no further temperature change.

(iv)      Tabulate the results as follows:

Procedures 2:

(i)           Measure 50cm³ of X₂ and put in 100cm³ plastic beaker. Record the initial temperature, T₁

(ii)        Measure 50cm³ of X₃ in measuring cylinder and measure its initial temperature, T₂ while in measuring cylinder.

(iii)      Pour X₃ solution from measuring cylinder to plastic beaker containing X₂, stir well to mix then measure the final temperature attained using the thermometer.

(iv)      Tabulate the results as follows:

Questions:

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE (MTWARA AND LINDI)

132/3A                                                         CHEMISTRY 3A

(For Both School and Private Candidates)

(ACTUAL PRACTICAL A)

TIME: 3:20 HOURS                                                                    Tuesday, 08^th February, 2022 a.m.

Instructions

1.    This paper consists of Three (3) questions.

2.    Answer all questions.

3.    Question one (1) caries (20 marks), questions two (2) and three (3) each caries (15 marks).

4.    Mathematical tables and Non programable calculator may be used.

5.    Write your Examination Number on every page of your answer booklet(s).

6.    For your calculations the following constants may be useful:

H=1, C=12, O=16, Cl=35.5, S=32, Na=23, Cu=64, K=39, Fe=56.

Universal gas constant, R=0.0821 Atm dm³mol⁻¹K⁻¹ or 8.314Jmol⁻¹K⁻¹

GMV= 22.4dm³

Specific heat capacity of solution= 4.2Jg⁻¹K⁻¹

Density of solution= 1g/cm³

1.    You are provided with the following:

X: A solution made by dissolving 0.79g of KMnO₄ in 250cm³ of solution

Y: A solution made by dissolving 13.90g of FeSO₄.XH₂O in 500cm³ of aqueous solution acidified with sulphuric acid..

Z: A dilute sulphuric acid Procedures:

(i)           Put X in the burette.

(ii)        Pipette 20 or 25cm³ of Y into conical flask. Add 20cm³ of Z to the same conical flask.

(iii)      Titrate the solution in conical flask against X in the burette until permanent pink colour just appear. Record the burette reading.

(iv)      Repeat procedure (i) to (iii) three times and tabulate your results as shown below.

Results:

The volume of the pipette used was......................cm³

The volume of the burette used was .......................cm³

Burette readings

Summary:

.............................. cm³ of Y required ................. cm³ of X for complete reaction.

Questions:

(a)      (i) Write the redox half reactions for this titration.

(ii)        Write the overall balanced ionic redox reaction.

(iii)      Indicate the species which is oxidant and the one which is reductant.

(b)     Explain why an indicator is not used in this kind of experiment.

(c)      Explain why sulphuric acid and not hydrochloric acid is used in a particular experiment.

(d)     Calculate:

(i)    Concentration of FeSO₄.XH₂O in g/dm³

(ii)Concentration of KMnO₄ in g/dm³

(iii)   Molarity of KMnO₄

(iv)    Molarity of FeSO₄

(v)  Molar mass of FeSO₄.XH₂O (vi) Value of X in the formula FeSO₄.XH₂O

2.    You are provided with the following:

K: 4g of hydrated sodium carbonate (Na₂CO₃.10H₂O)

J: 2g of anhydrous sodium carbonate Na₂CO₃

Thermometer, small plastic beaker and distilled water.

Procedures:

(i)  Measure 50cm³ of distilled water and put in small plastic beaker. Record the initial temperature, T₁ = .

(ii)  Dissolve 4g of Na₂CO₃.10H₂O in the small plastic beaker contain water while stirring record the final temperature of solution, T₂ = ................

(iii)  Discard the contents in the plastic beaker and wash it then measure 50cm³ of distilled water and put in the plastic beaker. As usual take the initial temperature of water using the thermometer, T₃ = ..............

(iv)  Take 2g of anhydrous sodium carbonate, dissolve in plastic beaker containing distilled water, while stirring record the final temperature, T₄ = ...................

Results:

Questions:

(i)       Calculate the heat change in each experiment.

(ii)      Calculate the molar heat change in each experiment.

(iii)      Calculate the heat of hydration of anhydrous sodium carbonate to hydrated sodium carbonate

(iv) Comment on the different in the molar heat change of solution for salt K and

L

3.    Sample Q contains a two cations and two anions. Use the information given in the experiment column to complete the observations and inferences and hence identify the two cations and the two anions

Calculation

(a)       The cations in sample Q are           .

(b)     The anions in sample Q are

(c)      Sample Q is a mixture of

(d)     Give one application of cation obtained in life.

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE (MTWARA AND LINDI )

132/2CHEMISTRY 2

(For Both School and Private Candidates)

Time: 3 HoursFriday, 04^thFebruary, 2022 p.m.

Instructions

1.This paper consists of six (6) questions.

2.Answer only five (5) questions.

3.Each question carries twenty (20) marks.

4.Mathematical tables and Non programable calculators may be used.

5.Cellular phones and any unauthorized materials are not allowed in the examination room.

6.Write your Examination Number on every page of your answer booklet(s).

7.For calculations you may use the following constants:

•Universal gas constant, R= 8.314JK⁻¹mol⁻¹or 0.0821K⁻¹atm mol⁻¹K⁻¹dm³

•Standard temperature =273K

•Standard pressure =1atm =760mmHg =1.0×10⁵Nm⁻²

•1 Faraday= 96500Cmol⁻¹

•GMV=22.4dm³

•1 Litre=1dm³= 1000cm³

•Velocity of light,C=3.0×10⁸m/s

•Atomic masses: Ag= 108, Cl= 35.5, Mn= 55, Fe= 56, I= 127

1.(a) (i) What is ideal solution.(01 mark)

(ii)Ideal solution differs from non-ideal solution by four areas, by using four points give factors contributes to ideal solution formation. (04 marks)

(iii)By using well labelled diagram show that Acetone and Ethanol mixture form a non-ideal solutions.(05 marks)

(b)When 0.7dm³of an aqueous solution containing 6g of a solute B per litre was shaken with 200cm³of heptanol, 3.21g of the solute B was extracted. Assuming the molecular state of the solute remained the same in both solvents, Calculate:

(i)Value of distribution coefficient.(03 mark)

(ii)Mass of the solute B which remained in the aqueous solution after a further shaking with 200cm³of heptanol.(03 marks)

(c)(i) What is steam distillation?.(01 mark)

(ii) Chlorobenzene which is insoluble in water is steam distilled at 98^◦C and atmospheric pressure of 101300Pa. A sample of steam distillate contains 247g of chlorobenzene for every 16g of H₂O. Calculate the vapour pressure of water and chlorobenzene at 98^◦C. (03 marks)

2.(a) Define the following terms as applied in chemistry

(i)Electric double layer (01marks)

(ii)Electrode potential(01marks)

(iii)Salt Bridge.(01marks)

(b)(i) Differentiate between Kohlrausch law and Ostwald dilution law.

(02 marks)

(ii)Give five applications of electrochemical series in life of chemistry.

2¹/₂marks)

(iii)Show the relationship between weak electrolyte

(c)(i) During supplying of food to students with silver tray it observed some silver particles were plated out from silver tray. How many grams of silver could be plated out on a serving tray by electrolysis of a solution silver +1 for a period of 8 hours at a passed current of 8.35amphere.

(04 marks)

(ii) What mass of NH₄Cl must be added to 0.5L of 1molL⁻¹NH₃solution to yield a solution with a PH of 9.0. Assume that no change in volume with Kb of 1.8 x 10^-5(03 marks)

(d)Give two components of buffer solution.(02 marks)

3.(a) Explain the following concepts:-

(i)Is there any reaction for which the rate does not change with the initial concentrations of the reactants?. (02 marks)

(ii)A lump of coal burns at a moderate rate in air while coal dust burns explosively.(02 marks)

(iii)Liquid bromide reacts slowly as compared to bromine vapour.(02 marks)

(iv)The energy of activation determines its rate.(02 marks)

(b)(i) What is half life of the reaction.(01 mark)

(ii) Consider the following reaction

If the rate constant K at 310^◦C and 420^◦C is 1.3×10⁻³dm⁻³mol⁻¹s⁻¹and 6.3×10⁻²dm⁻³mol⁻¹s⁻¹respectively, What is the activation energy E_afor the reaction?.(04 marks)

(c)The following table contains data which were collected at 298K for the reaction.

(i)Write down the rate expression for the reaction.(03 marks)

(ii)Calculate the order of the reaction with respect to each reactant and write the overall order of reaction. (04 marks)

4.(a) (i) Describe four features of coordination compounds.(04 marks)

(ii)Differentiate between charged complex from neutral complex. (02 marks)

(iii)How Ambidentante ligand differ from Monodentate ligand with example. (02 marks)

(b) Give explanations and equation when possible from the following observations.

(i)Sodium metal is very soft compared with magnesium metal.(01 mark)

(ii)Silicon tetrachloride (SiCl₄) can be hydrolysed by water, but carbon tetrachloride (CCl₄) cannot be hydrolysed. (01 mark) (iii) Aluminium metal does not react hot water or steam. (01 mark) (iv) F₂and Cl₂exists as gases, Br₂exist in the liquid form and I₂exist as solid.(01 mark)

(v) Lithium nitrate is decomposed thermally completely but potassium nitrate decomposed only partially.(01 mark)

(c) Briefly explain the extraction of aluminium from its principal ore, bauxite

(Al₂O₃.2H₂O) by Bayer’s Method.(07 marks)

5.(a) (i) What is a nucleophilic addition reaction.(01marks)

(ii)Describe the mechanism of nucleophilic addition reaction to a carbonyl compound.(03 marks)

(iii)Explain why ethanal are more reactive than acetone towards nucleophilic addition reaction.(02marks)

(b)Complete the following chemical reactions:

(c)An unknown ester E was found to have molecular formula C₅H₁₀O₂. When E was hydrolysed with water in the presence of mineral acid, it produced carboxylic acid F with alcohol G. The treatment of G with SOCl₂gave an alkyl chloride H. When H was treated with KCN, a product I was formed which on hydrolysis with water and acid produced carboxylic acid F.

(i)Use this information to deduce the structure and name of the original ester. (02 marks)

(ii)Identify F to I and write all chemical reactions involved.(06 marks)

6.(a) An organic compound C₂H₄O gives red precipitate when warmed with Fehling’s solution. It also undergo aldol condensation in the presence of NaOH.

(i)Write structure and IUPAC name of the compound.(01 mark)

(ii)What is the state of hybridization of the carbon atoms in the compound.

(01 mark)

(iii) Write all reactions involved in the compound.(02marks)

(b) Show how the following conversion may be achieved.

(c) An ester A (C₄H₈O₂), on treatment with excess methyl magnesium chloride followed by acidification, gives an alcohol B as the sole organic product. Alcohol B, on oxidation with NaOCl followed by acidification, gives acetic acid.

1. Decide the structure of A and B
2. Show all reactions involved

PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

MOCK EXAMINATION SOUTHERN ZONE

(MTWARA AND LINDI)

132/1CHEMISTRY 1

(For Both School and Private Candidates)

Time: 3 HoursWednesday, 02^ndFebruary, 2022 a.m.

Instructions

1.This paper consists of sections A and B with a total of ten(10) questions.

2.Answer ALL questions in section A and two(2) questions from section B.

3.Mathematical tables and non-programable calculators may be used.

4.Cellular phones and any unauthorized materials are not allowed in the examination room.

5.Write your Examination Number on every page of your answer booklet(s).

6.The following information may be used.

(a)Universal gas constant, R=8.314JK⁻¹mol⁻¹or 0.0821atmdm³mol⁻¹.

(b)Rydberg constant R_H= 1.09678×10⁷m⁻¹

(c)standard pressure =1 atm=760mmHg=1.0× 10⁵N/m²

(d)1 Mass of electron= 9.11×10⁻³¹kg

(e)Density of water= 1g/cm³

(f)Velocity of light, C= 3.0×10⁸m/s

(g)Avogadron’s constant =6.022×10²³mol⁻¹

(h)1A˚ = 1.0×10⁻¹⁰m

(i)Planks constant, h= 6.63×10⁻³⁴Js

(e) Atomic masses

H=1, C=12, O=16, N=14, Cl=35.5, Br=80, Na=23.

This paper consists of six printed pages

SECTION A (70 MARKS)

1.(a) Differentiate

(i)Emission spectra and absorption spectra

(ii)Line spectra and continuous spectra

(iii)Atomic orbital and degenerate orbital(03 marks)

(b)What is the wavelength of a photon (in nanometers) emitted during a transition from the fifth to second energy levels in hydrogen atom? To what region of the spectrum does this wavelength correspond? (04 marks)

(c)Suppose that the uncertainty in determining the position of an electron circling an atom in an orbit is 0.4A˚. What is the uncertainty in the velocity? (03 marks)

2.(a) What do you understand by

(i)Octet rule

(ii)hybridization of atomic orbital

(iii)Orbital(03 marks)

(b)Using sketches, briefly explain three possible overlaps that can lead to formation of a sigma bond

(c)Give two reasons for the observed difference in bond strength between sigma and pi bonds in compounds.

(d)Predict the geometry of water, basing on the valence shell Electron pair Repulsion (VSEPR) theory.

3.(a) What do you understand by lattice enthalpy? What is its significance? (02 marks)

(b)Some values of lattice enthalpies/kJ/mol are NaCl-771, KCl-707, NaF-918, CsF-747, NaI-699, MgO-3791, BaO-3054. Comment on differences of lattice enthalpies of

(i)NaCl and KCl

(ii)NaCl and NaF

(iii)MgO and BaO

(iv)NaCl and MgO(04 marks)

(c)Construct a Born-Haber cycle, and use it to calculate the standard lattice energy of cadmium (II) iodide

4.(a) (i) What is an ideal gas?

(ii) The pressure exerted by 12g of an ideal gas at temperature t⁰C in a vessel of volume V litres is one atmosphere. When the temperature is increases by 10%. Calculate the temperature t and volume V. Molecular mass of the gas = 120u(04marks)

(b)Two flasks at the same temperature are joined by a glass tube with a stopcock. Flask A is a 4.0L flask containing N_2(g)at 2.0 atm, while flask B is a 10.0L flask containing carbon monoxide gas at 1.4 atm. calculate the total pressure when the stopcock is opened. (02marks)

(c)A straight glass tube has two inlets X and Y at the two ends. The length of the tube is 50cm. HCl gas through the inlet X and NH₃gas through the inlet Y are allowed to enter the tube at the same time. White fumes first appear at a point P inside the tube. Find the distance of P from X (03 marks)

5.(a) The Oxo-acids have acidity strength in the order HClO₄>H₂SO₄>H₃PO₄.

Explain the trend of acidity of these oxo-acids.(03 marks)

(b)With the aid of chemical equation (s) explain how you can prepare soluble chlorides.(04 marks)

(c)By the aid of chemical equations describe the following

(i)Basic oxides

(ii)Amphoteric oxides

(iii)Acidic oxides(03 marks)

6.(a) Explain the following

(i)Homogeneous catalyst

(ii)Heterogeneous equilibrium

(iii)Dynamic equilibrium(03 marks)

(b)Consider the following gas phase reaction equilibrium involving N₂O₄.

Reaction 1: N₂O_4(g)2NO_2(g)k₁= 0.115

Reaction 2: 2N₂O_4(g)2N₂O_(g)k₂= 1.37×10⁻¹

Determine the equilibrium constant of the reaction.

(c)At the start of a reaction, there are 0.249 mol N₂, 3.21×10−₂mol H₂, and 6.42×10⁻⁴mol NH₃in a 3.50L reaction vessel at 375^◦C. If the equilibrium constant (kc) for the reaction N_2(g)+3H_2(g)→2NH_3(g)is 1.2 at this temperature, decide whether the system is at equilibrium. If it is not, predict which way the net reaction will proceed to achieve equilibrium.(04 marks)

7.(a) Distinguish sigma bond from pi bond(03 marks)

(b)Predict the shapes of the following molecules using VSEPR theory

(i)AsF₅

(ii)PCl₃

(iii)SF₆(03 marks)

(c)(i) Although both CO₂and H₂O are triatomic molecules, the shape of H₂O molecule is bent while that of CO₂is linear. Explain this on basis of dipole moment.

(ii) Write two significance of dipole moment.(04 marks)

SECTION B (30 MARKS)

8.(a) Account for the following

(i)Benzene undergo addition reactions under harsh conditions.

(ii)Nucleophilicity of benzene is affected by the substituent attached to it

(iii)Halogens are deactivators but direct the coming electrophiles to ortho and para positions.(03 marks)

(b)Compound A, C₇H₁₄is treated with bromine in presence dichloromethane to give B, C₇H₁₄Br₂. Compound B is treated with NaOH in presence of ethanol followed by NaNH₂resulting in the formation of C. Compound C react with hydrogen in presence nickel catalyst to form 2-methlyhexane. Compound C have no reaction with ammoniacal silver nitrate. Ozonolysis of A gives aldehyde D and ethanal . Deduce the structure formula of A, B, C and D.

Write all the chemical reactions.(05 marks)

(c)Three hydrocarbons, D, E and F, all have the molecular formula C₆H₁₂. D decolourises an aqueous solution of bromine and shows geometric isomerism. E also decolourises an aqueous solution of bromine but does not show geometric isomerism. F does not decolourises an aqueous solution of bromine. Draw the structural formula of D, E and F. Write all the chemical reaction.(02marks)

(d)How the following conversion can be achieved in not more than four steps.

(i)Butylchloride to But-1-yne(01marks)

(ii)Ethene to benzene(01marks)

(iii)But-1-ene to Butan-2-one.(01marks)

9.(a) Explain the difference between the boiling temperatures of the following compounds:

(01marks)

(b)Arrange the following products according to the percentage (%) yield obtained from the nitration of ter-butylbenzene. Justify the order.

(d)Give one chemical test to distinguish the following

(i)But-2-ene and butane

(ii)Benzyl chloride and chlorobenzene

(iii)1-chloropropane, 2-chloropropane and 2-chloro-2methylpropane

(04marks)

10.(a) Define the following terms

(i)Liming

(ii)Cation exchange capacity

(iii)Percentage base saturation

(iv)Macronutrients(04 marks)

(b)A soil sample was collected from certain farm for laboratory analysis. After being analyzed the soil had the following exchangeable cations.

Ca²⁺= 30meq/100g

Mg²⁺= 16meq/100g

K⁺= 39meq/100g

H⁺= 4meq/100g

(b) How many milligrams of these elements were in the soil and what is the percentage base saturation of the soil sample. (07 marks)

(c) Mention four (4) factors of which influence the soil acidity? (02 marks)

(d) (i) What are the benefits of liming?(mention any four) (02 marks)

(ii) Not all calcium and magnesium compounds are suitable for liming.

Explain(02 marks)