THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL OF TANZANIA ADVANCED CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

132/1 CHEMISTRY 1

(For Both School and Private Candidates)

Time: 3 Hours Year: 2011

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. Each question carries ten (10) marks in section A and fifteen (15) marks in section B.

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

5. Cellular phones and any unauthorised 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

Rydberg constant, R_H=1.09678x 10⁷m^-1

Gas constant, R = 8.31JmoI^-1K^-Ior 0.0082 atm mol^-1K^-Idm³

GMVat s.t.p.22.4dm3

1 litre = 1 dm³=1000cm³

At STP: Temperature = 273K, Pressure = 760mmHg

Planck constant, h=6.63x 10^-34Js

Velocity of light, C = 3.0 x 10⁸m/s

Atomic masses H = 1, C = 12, N = 14, O-16, Na-23

1.Define the following terms:

(i)Alpha particles

(ii)Beta particles

(ii)Isotope

(iv)Nuclear Fission

(b)A radioactive isotope of polonium 2%Po decays according to the following scheme:

(i)Deduce the mass numbers and atomic numbers of X, Y and Z.

(ii)What is the relationship between the element PO and Z?

(c) The element europium, Eu exists in nature as two isotopes; 151Eu with a mass of 150.9196 a.m.u and¹⁵³Eu with a mass of 152.9096 a.m.u. If the average atomic mass of europium is 151.96 a.m.u, calculate the percentage relative abundances of the two isotopes.

2.What is the meaning of the following quantum numbers?

(b)List all possible values oft and m when n is 3.

(c)When an electron jumps from a certain higher energy level E , to its ground state El, green light in the Balmer series is emitted. If the energy Released during thistransition is 4.071 x 10 19 J determine the:

(i)Wavelength of the green light

(ii)Higher energy level, E2 from which the electron jumps to the ground energy level El.

3.What do you understand by the following types of bonds?

(i)Dative covalent bond.

(ii)Inter-molecular hydrogen bond.

(iii)Covalent bond.

(iv)Intra- molecular hydrogen bond.

(b) (i)At 110⁰C and 454 mmHg. 0.1 lg of ethanoic acid vapour occupies 63.7cm³. At 156⁰C and 458mmHg, 0.081g of ethanoic acid vapour occupies 66.4cm³. Calculate the molar mass of ethanoic acid in the vapour phase at each temperature.

(ii)Give the interpretation of the results in 3(b)(i)above.

4.(a) State the following:

(i)Graham's law ofgas diffusion.

(ii)Dalton's law of partial pressures.

(b)A 3.20m³vessel contains a mixture of 86.2g of oxygen and 1.5g of hydrogen at 88⁰C. Calculate the total pressure in the vessel.

(c)Gas A of a certain volume diffuses for 580.8s while the same volume of gas J diffuses for 300s under identical experimental conditions. Calculate the relative molecular mass of J ifthe relative molecular mass gas A is 120.

5.(a) (i) State the partition law.

(ii) Explain the meaning of miscible solutions.

(b)18g of compound X distribute themselves between water and equal volume of an immiscible solvent Y so that 2g of X are in water. Calculate to the nearest integer, the percentage of X left in water if 1000cm³of water containing lg of X are extracted by one litre of Y.

6.(a) State the following:

(i) Equilibrium law

(ii) Le Chaterlier's law

(b)In the preparation of ethylethanoate shown in the equation below, concentrated H₂S0₄is often added to the mixture.

(i)State two (2) functions of concentrated H₂S0₄in the production of the compound.

(ii)What will be the effect of adding NaOH(aq) instead of conc. H2S04 in the production of compound?

(c) (i) When 1.00moI/dm³of CH₃COOH were heated with 0.18 mol. of C₂H₅0H in a Idm³closed vessel, 0.829mol. CH COOH remained at equilibrium. Calculate the value of K .

(ii) What mass of ethylethanoate should be present in the equilibrium mixture formed under the same experimental conditions as 6(b)(i) above if 0.30 moles of ethanol were heated with 0.20 moles of ethanoic acid in 1.0dm³closed vessel?

7. (a) Explain why the first element in each group of the main periodic table shows properties which are not exhibited by other group elements.

(b)Account for the following observations and give chemical reactions whenever

necessary:

(i)The second electron affinity is always positive

(ii)Magnesium carbonate decomposes readily when heated while sodium carbonate has no action to heat.

(iii)Alluminium utensils rust quite easily.

(iv)Water is covalent compound but has a high boiling point.

(v)Hydrogen gas is evolved when magnesium metal is placed in a beaker containing ammonium chloride.

(c)Justify the periodicity of properties of elements in the periodic table based on electronic configuration.

(ii)What are s, p and d block elements of periodic table?

8.(a)Account for the following:

(i) Zinc and iron are both d-block elements but iron can be magnetized while zinc cannot.

(ii)Iron (Il) sulphate is green while zinc sulphate is white.

(b)(i) Manganese is said to exhibit variable oxidation numbers. List them.

(ii) Write the electronic configuration of manganese.(Atomic number = 25)

(iii)Give examples of compounds in which manganese exhibits different oxidation state. (Give example in each case.)

9. (a) State the following:

(i) Zeeman effect

(ii) Pauli's exclusion principle

(iii) Hund's rule of maximum multiplicity.

(b) (i) What is effective nuclear charge?

(ii) The first ionization energy of aluminum is less than that of magnesium. Giving reasons compare the second ionization energy of aluminum to that of magnesium.

(c) Explain why the CI-C-O bond angle in C1₂CO is 124⁰C and not 120⁰.

10.(a)Account for the uniqueness of hydrogen in the periodic table.

(b)(i) List all the isotopes of hydrogen and explain how they differ from one another.

(ii)Give the products of the following reactions:

© Distinguish between ortho and para hydrogen.

11.(a) Name the following compounds according to the IUPAC system:

(b)Compound X containing a carbon-carbon double bond would react with the following reagents:

(i) Y to form 2 - bromo - 2 - methylbutane

(ii)Z to form (CH₃)₂CHC(OH)(CH₃)₂

(iii)W to form 2 - chloro -2 - methylbutane.

Name compound X and reagents Y, Z and W

(c)Indicate a chemical test which may be used to distinguish the members of each of the following pairs. Indicate of the pair that gives the positive or greater reaction.

12. (a) Explain briefly the following terms:

(i)Nucleophiles

(ii)Nucleophilic substitution

(b)Arrange the following compounds in order of increasing easiness in substitution of the halogen atom by an electrophile. Give reasons for your arrangement

(c)Explain the fact that nucleophilic substitution reaction in I-bromobutane is bimolecular whereas nuncleophilic substitution reaction in 2-methyl-2bromopropane is monomolecular.

13.(a) Write the structural formulae of the following compounds:

(i) 2,4-dinitrophenoI (ii) p-aminophenol.

(b)Give the names and structures of dimethyl benzenes.

(c)Explain with the help of chemical equations which dimethyl benzene in 131b) above will yield:

(i)one (l)mononitrito product

(ii)two(2) mononitrito product

14.Give the organic product(s) of each of the following reactions:

(b)Describe the chemical test you would carry out to distinguish the following compounds: