THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL OF TANZANIA

FORM TWO NATIONAL ASSESSMENT

032   CHEMISTRY

Duration: 2:30 Hours

INSTRUCTIONS. 

1. This paper consists of sections A and B with a total of ten (10) questions.
2. Answer all questions in spaces provided.
3. All writing must be in blue or black ink except drawing which must be in pencil.
4. Calculators, cellular phones and any unauthorized materials are not allowed in the examination room.
5. Write your Examination Number at the top right corner of every page.
6. The following atomic masses may be used; H =1, N =14, O = 16, S = 32, Ca = 40

SECTION A (20 Marks)

Answer all questions in this section.

1. For each of the items (i) –(x), choose the correct answer from the among the given alternatives and write its letter in the box provide.

(i) What is the best way of keeping a clean test tube after use?

1. Keeping it in water
2. Keeping it on a test tube holder
3. Keeping it in a basin for test tubes
4. Keeping it on a test tube rack.

(ii) Which one of the following does not involve the processes of urban water treatment and purification?

1. Sedimentation
2. Distillation
3. Filtration
4. Chlorination.

(iii) Why hydrogen gas is not a constituent of air?

1. Because of being water soluble
2. Because of being denser than air
3. Because of being very light
4. Because of being highly flammable.

(iv) Which is the suitable alternative heat source to be used in absence of Bunsen Burner?

1. Torch and spirit burner
2. Torch and kerosene stove
3. Kerosene stove and spirit burner
4. Firewood and torch.

(v) Which group and period does the element with 11 electrons belong?

1. Group I and period 3
2. Group II and period 1
3. Group I and period 1
4. Group II and period 3.

(vi) What happens when substance A reacts with substance B to form a new substance C?

1. Substance A and B are said to have formed a solution
2. Substance A and B are said to have undergone a physical change.
3. Substance A and B are said to have undergone a chemical change.
4. Substance A and B are said to have undergone a dissolution.

(vii) Which components make fire triangle?

1. Oxygen, fuel and heat
2. Oxygen, nitrogen and heat
3. Oxygen, fuel and carbon dioxide
4. Oxygen, heat and hydrogen.

(viii) Which state is involved when drying wet clothes?

1. Liquid to solid
2. Solid to gas
3. Gas to liquid
4. Liquid to gas.

(ix) Which net charge exists in radicals?

1. Zero
2. Positive or negative
3. Neutral
4. Positive and negative.

(x) Why Non – luminous flame is the most applicable flame for heating purposes?

1. It is very nosy
2. It has no soot.
3. It is very hot
4. It has air holes open

2. (a) Match each item in List A with a correct response in List B by writing the letter of the correct response below the corresponding item number in the table provided.

   (b) Fill in the blank spaces by using the appropriate terms

(i)     In an atom, the effect of the charged nucleons is balanced by the charge of……………..

(ii)  Serum is separated from blood samples by employing a technique called………………..

(iii) Boiling points of substances reflect the strength of……………….

(iv) Grinding chalk into a powder involves changing the state of …………………….

(v)   The insoluble substances formed during filtration are collectively termed as ……………….

SECTION B (80 Marks)

Answer all questions in this section.

3. (a) State one use of each of the items (i) – (x) in administering First Aid.

(b) Give one function of each of the following apparatus in the chemistry laboratory.

(i) Spatula…………… …………… ……………….

(ii) Gas jar…………… …………….  …… ……….

(iii) Lie – big condenser …………… …… ………… 

(iv) Motor and pestle…… …………… …………… View Ans

(v) Wire gauze… ………… ………… …………….

4. (a) By giving one reason, explain the following facts.

(i)     During laboratory preparation of oxygen gas, little manganese dioxide is added to hydrogen peroxide

………… ………… ……… …………… 

………… ……… …………… ……………

(ii)  Fish can obtain oxygen for respiration although spend their lives in water.

…………… …………… ……………

 ………………… …….......... ....... ....

(iii) Oxygen gas can be used for welding activities although it does not burn.

……………… ……………… …… 

…………… ……………………… 

 (b) Which property enables the use of hydrogen gas in: 

(i)     Filling weather balloons?

……………… ………………… ……… ……… 

(ii)  Production of oxy – hydrogen flame?

………… ………… ………………………… ….

 (c) Give two domestic uses of oxygen gas.

(i)     ……………… ……………………… 

(ii)  ……………… ……………………… 

5. (a) Give three chemical tests for water and show the results obtained in each.

(i)     ………… …………… …………………

(ii)  ………… ……………… ………………

(iii) ………… ……………… ………………

(b) (i) Differentiate water treatment from water purification.

……… ……… ……………… … 

……… ……… … ……… ……… 

(ii) Why drinking water should be treated and purified? Give two reasons.

(i)     ………………… ………………… …… 

 (iii) How can drinking water be treated or purified?

(i)     ………… …………………… …… ….

(ii)  …………… ……………… ……… ….

(iii) … ……… ………………… ……… ….

6. (a) Differentiate hypothesis from analysis.

…………… ………………… ……

……… …………………… ………

 (b) Effective use of the four senses of observation is important before a chemist can make conclusion. With four points, show how the senses are used as tools of observation during experimentation by giving one example for each.

(i)     ………… ………… ……………

(ii)  ………… …………… ………….

(iii) ………… ……………… …… ….

(iv) ………… …………… ……………

7. What precautions will you take in handling chemicals having the warning signs shown in the table? Give two precautions in each sign.

8. Briefly explain the five classes of fires based on the nature of the burning material and the extinguisher required. Give one example for each class.

a)      ……… ………… ………………… …………………

b)     …………………… ………………………… ……… 

9. A certain gaseous compound contains 30.4% of nitrogen and 69.6% of oxygen by mass. If the molar mass of the compound is 92, calculate its molecular formula. 

………………… ………………… ………………

………………… …………………… …………… 

…………………… …………………… …………

10. Briefly explain five characteristics to be considered when looking for a good fuel.

(i)     ………………… …………………  

(ii)  ………………… …………………  

(iii) ………………… …………………  

(iv) ………………… …………………  

(v)   ……………… ……………………