FORM FOUR CHEMISTRY NECTA 2012

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

032/1  CHEMISTRY 1

 (For Both School and Private Candidates)

Time: 3 Hours  Thursday, 11th October 2012 p.m.

 Instructions

  1.  This paper consists of sections A, B and C.
  2.  Answer all questions in this paper.
  3.  Calculators and cellular phones are not allowed in the examination room.
  4.  Write your Examination Number on every page of your answer booklet(s).
  5.  The following constants may be used.

 Atomic masses:

 H = 1, C = 12, O = 16, N = 14, Na = 23, Mg = 24, Al = 26, S = 32, Cl = 35.5, Ca = 40, Mn = 55, Fe = 56, Cu = 64.

 Avogadro’s number = 6.02 x 1023.

 GMV at s.t.p. = 22.4 dm3.

 1 Faraday = 96,500 coulombs.

 Standard pressure = 760 mm Hg.

 Standard temperature = 273 K.

 1 litre = 1 dm3 = 1000 cm3.

SECTION A (20 Marks)

Answer all questions in this section.

1. For each of the items (i) – (x), choose the correct answer from the given alternatives and write its letter beside the item number in the answer booklet provided.

(i)  Which one of the following sets of laboratory apparatus are used for measure volume?

  1. Crucible, U-tube and volumetric flask
  2. Test tubes, beakers and glass jar
  3. Thistle funnel, separating funnel and beaker
  4. Burette, pipette and measuring cylinder
  5. Conical flask, test tube and measuring cylinder.
Choose Answer :


(ii)  The empirical formula of certain compound in CH3. Its molar mass is 30 g. What will be its molecular formular?

  1. CH4
  2. C2H4
  3. C2H6
  4. C2H8
  5. C4H12
Choose Answer :


 (iii)  In order to produce the greatest amount of hydrogen in a short time, one gram of magnesium ribbon should react with

  1. 10 cm3 of 0.5 M sulphuric acid
  2. 40 cm3 of 0.5 M acetic acid solution
  3. 40 cm3 of 0.5 M sulphuric acid solution
  4. 20 cm3 of 1 M sulphuric acid solution
  5. 20 cm3 of 1 M acetic acid solution.
Choose Answer :


(iv)  Fractional distillation process of a mixture of water and ethanol is possible because

  1. water and ethanol have the same boiling point
  2. water has lower boiling point than ethanol
  3. ethanol has lower boiling point than water
  4. water and ethanol form partially immiscible liquid solution
  5. water and ethanol are immiscible liquids.
Choose Answer :


 (v)  Which of the following substances represent a group of acidic oxides?

  1. Carbon dioxide, carbon monoxide and sulphur dioxide
  2. Sulphur trioxide, nitrogen dioxide and nnitrogen monoxide
  3. Carbon dioxide, sulphur dioxide and dinitrogen oxide
  4. Sulphur trioxide, carbon dioxide and nitrogen dioxide
  5. Carbon monoxide, nitrogen oxide and sulphur dioxide.
Choose Answer :


 (vi)  What will the molarity of a solution which contains 26.5 g of anhydrous sodium carbonate in 5 dm3 of solution?

  1. 0.05 M
  2. 0.25 M
  3. 5.30 M
  4. 0.025 M
  5. 0.50 M
Choose Answer :


 (vii)  The Brownian movement is taken to be the evidence of the:

  1. theory of association of water molecules
  2. theory of ionization of electrolytes
  3. theory of colloidal suspensions
  4. kinetic theory of behavior of substances
  5. Brownian theory.
Choose Answer :


 (viii)  One off the isotopes of an element X has an atomic number Z and a mass number A. What is the number of neutrons contained in the nucleus of the element X?

  1. Z
  2. A
  3. A + Z
  4. A – Z
  5. Z – A
Choose Answer :


(ix)  C2H4Cl can be represented in different structures which are called

  1. homologous series
  2. isomers
  3. structural formulae
  4. identical structures
  5. condensed structures.
Choose Answer :


(x)  _____ is the general term used to explain a mixture of different metals.

  1. Alloy
  2. Allotrope
  3. Amphoteric
  4. Amorphous 
  5. Isotope.
Choose Answer :


2. Match the items in List A with the responses in List B by writing the letter of the correct response beside the item number in the answer booklet provided.

LIST A LIST B
  1. Its hydride is the only alkaline gas.
  2. Possesses 11 electrons.
  3. Most electronegative element.
  4. Extracted by Frasch process.
  5. A noble gas.
  6. Exists in oxidation state of +3 in haematite.
  7. Least reactive metal in the reactivity series of metals. 
  8. A non metal which is a good conductor of heat and electricity.
  9. Vital for all living things
  10. Its oxide is yellow when hot and white when cold.


  1. Sodium
  2. Aluminum
  3. Iron
  4. Gold
  5. Oxygen
  6. Flourine
  7. Sulphur
  8. Argon
  9. Ozone
  10. Iodine
  11. Mercury
  12. Chlorine
  13. Magnesium
  14. Calcium
  15. Nitrogen
  16. Carbon
  17. Lithium
  18. Potassium
  19. Hydrogen
  20. Zinc 
View Ans


SECTION B (54 Marks) 

Answer all questions in section.

3. (a) With the help of chemical equation, what will be observed when ammonia reacts with

(i) Hydrogen chloride.

(ii) Copper (II) oxide.

(b) It is not advisable to sleep inside a house which is not well ventilated with a burning wooden charcoal. Give a reason for that and write the chemical equation to represent your answer.

View Ans


4. Study the following part of the periodic table and then answer the questions that follow. Note: The letters used are not scientific symbols for the elements concerned.

Group

(a) Identify and write down the electronic configuration for the elements K, N, P and L.

(b) What type of bond will exist in a compound formed when Q combines with L? Write the chemical formula for the compound formed and list two chemical properties for the compound formed.

View Ans


5.  (a) A solution of sodium hydroxide was electrolysed using platinum electrodes. Write the reactions which took place at the electrodes and give a reason why the solution becomes alkaline. 

View Ans


(b) Electric current was passed through a solution of sodium hydroxide using platinum electrodes. Draw a labelled electrolytic cell for this electrolysis. Indicate the directions of the movement of ions. 

View Ans


6. (a) Give the name of the process of making coke from coal. Write one characteristic which make coke a better fuel than coal.

View Ans


(b)(i) State the difference between physical strength and chemical strength of metals.

(ii) Giving example, explain why preparation of metallic oxides by direct method is not intensively used. 

View Ans


7. (a) (i) People suffering from heart burn usually use wood ashes for relief. Mention characteristic which makes the ashes to be used for heart burn relief.

 (ii)Give four compounds found in laboratories which show the same characteristics as ashes.

View Ans


 (b) How many molecules are there in 11.2 litres of carbon dioxide at STP? 

View Ans


8. (a) (i) Name the products formed when nitrates of potassium and zinc decompose by heat. 

 (ii) Suggest why the nitrates of zinc and potassium behave differently on heating.

View Ans


(b) Mention two uses of sodium nitrate.

View Ans


9. Two experiments were carried out using the same mass of magnesium ribbon and the same volume of acids of the same concentration. The acids were 1M hydrochloric acid and 1M ethanoic acid. The results were as shown in the following figure:

 (a) If the experiments were conducted within the same time, is there a difference in volumes of hydrogen gas collected at the same room temperature and pressure? Give reasons for your answer.

 (b) When same mass, volume and concentration of powdered magnesium and ethanoic acid are allowed to react, new graph is formed. Giving reason (s), suggest the position of that graph whether will be above, between or below graphs A and B. 

View Ans


10. (a) (i) Name three gases which should not be produced in order to prevent the destruction of ozone layer. 

 (ii) List and explain three effects of ozone layer depletion.

View Ans


(b) Lack of safe water for domestic and industrial uses is a serious problem in most of Tanzanian towns. The major cause of this problem is pollution in the water sources. Slate three methods that could make water from a pond or a well be safe for drinking.

View Ans


11. (a) The chemical properties of concentrated sulphuric acid can be grouped into oxidizing property and dehydrating property. In which property should sulphuric acid be grouped when it reacts with copper metal? Give reason and write the equation of the reaction.

View Ans


 (b) The preparation of chlorine gas can be represented by the following equation: MnO2 + 4HCl ? MnCl2 + 2H2O + Cl2. Calculate the number of moles of HCl which are needed to react with 20 g of MnO2 and list two main chemical properties of chlorine gas.

View Ans


SECTION C (26 Marks) 

Answer all questions in this section. 

12. Consider a four carbon hydrocarbon (C4Hn), where n is an integer. Give the name of homologous series, molecular formula and structural formula for different isomers of the compound formed by each homologous. In each case indicate the causes of isomerism. 

View Ans


13.Describe four common stages for the extraction of metals. Does the extraction of gold follow all four stages? Give reasons.

View Ans


Download Learning
Hub App

For Call,Sms&WhatsApp: 255769929722 / 255754805256

GO TO NECTA EXAMS