FORM TWO CHEMISTRY NECTA 2012

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATION COUNCIL

CHEMISTRY FTNA 2012

(i)All domestic utensils made of iron undergo rusting when exposed to:

  1.  Air and fire
  2.  Air and oil
  3. Air and water 
  4. Water and oil
Choose Answer :


(ii)When a small amount of common salt is dissolved in a glass of water the mixture formed is:

  1. Heterogeneous 
  2. Homogeneous 
  3. Immiscible 
  4. Suspension
Choose Answer :


(iii) A chemist should acquire all of the following skills except:

  1. Experimentatio
  2. Observation 
  3. Problem identification 
  4. Surgery
Choose Answer :


(vi) An important property of oxygen which distinguishes it from other gases is that it:

  1. Burns and supports combustion
  2. Burns but does not support combustion 
  3. Neither burns nor supports combustion
  4. Supports combustion but does not burn
Choose Answer :


(v) The process of chlorination in water treatment aims at:

  1. Forming suspension 
  2. Killing micro-organisms 
  3. Making syrup 
  4. Removing bad odour
Choose Answer :


(vi) One of the following is not correct about coke being a better fuel than coal as it:

  1. Does not produce carbon dioxide gas
  2. Does not produce poisonous gas
  3. Has a higher heat content 
  4. Is clean and smokeless
Choose Answer :


(vii) Class E fire can best be extinguished by using:

  1. Carbon dioxide 
  2. Fire blanket
  3. Sand 
  4. Water
Choose Answer :


(viii)The following is a set of apparatuses which are used for heating:

A.crucible, test tube, evaporating dish

B.evaporating dish, tongs, crucible

C.test tube, evaporating dish, tongs

D.tongs, crucible, test tube

Choose Answer :


(ix)Which of the following methods can be used to get oil from cotton seeds?

A.Decantation  

B. Distillation

C. Grinding and distillation 

D. Grinding followed by squeezingChoose Answer :



(x)Which of the following apparatuses is suitable for measuring volumes of smaller quantities of liquids?

A.Beaker    

B. Burette

C. Conical flask 

D. Measuring cylinder

Choose Answer :


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

LIST A

LIST B

(i)A method used to separate mixtures of two or more liquids that form homogeneous solution by means of fractional column.

(ii)A substance that absorbs moisture from the atmosphere and dissolves in it.

(iii)Elements with stable structure.

(iv)Molecular mass of calcium carbonate.

(v)Poisonous gases prepared in it.

(vi)Produces a "pop" sound.

(vii)Quiet and unsteady flame.

(viii)Smokeless solid fuel.

(ix)Source of energy derived from animal waste,

(x)Used to prevent direct heat to reach the apparatus.

A. Biogas

B. Chromatograph

C. Coke

D. Corrosive

E. Deliquescent

F. Fractional distillation

G. Fume chamber

H. Hydrogen

I. Luminous flame

J. Noble gases

K. Non-luminous flame

L. Oxygen

M. Wire gauze 

N. 80g/mol 

O. 100g/mol.

View Ans


SECTION C

3.         (a) Mariam was preparing food for her family using hot oil in a frying pan. Accidentally the pan tripped over and a huge fire spread over her kitchen floor.

(i)Mention two extinguishers which would be appropriate for putting out the fire.

(ii)Which fire extinguisher would be dangerous to use when trying to put out the fire in (a) above? Give reason. (b) Mention three conditions for a fire to start.

(c) (i) What is combustion?

(ii) Give three areas where combustion is applied.

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4.         (a) In an experiment, two iron nails A and B were used whereby painting was applied on nail A. The two nails were placed in a moist environment and after one month the weight of each nail was determined. Which of the two nails would be heavier? Give reason.

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(b)State the method which will be used to protect each of the following from rusting:

(i)Covering iron sheets with a layer of most reactive metals (ii) Bicycle chain

(c)  Find the oxidation number of the underlined elements in the following:

(i)Mn04

(i) K2C%07

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5. Use the details given below about elements P, Q, R, S and T to answer questions (a) and (b).

Element
Atomic number
Atomic Mass
P
10
20
Q
11
23
R
12
24
S
13
26
T
14
32

(a) (i) Write down the electronic configuration of the elements represented by letters from P to T:

(i)How many neutrons are present in element Q? .

(c)Name the type ofbonds that will be formed in the combination between the following elements: (i) Q and T

(ii) S and T

(d)Write the chemical symbol for each of the following elements:

(i)Silver 

(ii)Lead .........

(iii)Manganese ......

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6.         (a) Explain why petroleum and coal are non-renewable resources of energy. (b) What is fuel?

 The problem facing Tanzania society is misuse of charcoal and firewood as a source of fuel. Give two points of advice to the society on how to use less charcoal and firewood efficiently.

(d) Mention three categories of fuel and give two examples in each category.

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(a) List down four careers that are a result of studying Chemistry.

 The following are possible causes of accidents which can occur in the Chemistry laboratory. State how you can avoid them.

(i)Poisonous chemicals left in an unlocked cupboard .........

(ii)A student picking up a bottle containing concentrated H2S04 acid by the neck .........

(iii)Concentrated acids stored in the upper most shelf of cupboard

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8.An experiment showed that 13.88g of calcium chloride were obtained from the combination of 5g of calcium with unknown relative mass of chlorine.

(i)What is the simplest formula of calcium chloride .

(ii)What kind of bond exists between calcium and chlorine?

(iii)Give two properties of the bond you have mentioned in (ii) above.

(b)      Define the following terms as applied in Chemistry

Decantation

Filtration

(iii)Picking

(iv)Funnel Separation

(c) (i)Which is the most abundant element on the earths outer crust? (ii) The term used for acidic chemicals which can burn your skin is

(iii) Give the name of a flame which forms soot .........

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9.(a) Explain why:

(i)a magnesium ion has a charge of 2+ .........

(ii)a magnesium oxide has no overall charge ..

(b)       Give the name of a bond which can be formed between two oxygen atoms .......

(c)      (i) State the modern periodic law

(ii)Give the special name for each of the following groups of elements in the periodic table:

Group I

Group Vll .........

(iii)Why is the atomic number a better way of identifying an element than the mass number? .

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10.(a) Mention four physical properties of water.

(b)      What will happen when:

(i)       a burning splint of wood is introduced into a gas jar containing oxygen gas

(ii)     oxygen gas reacts with metals .

(iii)   hydrogen gas reacts with oxygen gas .........

(c)      List four uses of hydrogen in our daily life.

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