🌊PAPER 55-Qns

PRESIDENT’S OFFICE REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT IRINGA REGION 23, FORM

IRINGA REGION ANNUAL JOINT EXAMINATION

CHEMISTRY 032

Time: 3 Hours

Wednesday, 22 nd November 2023 a.m

Instructions.

1. This paper consists of section A carrying 16 marks, section B carrying 54 marks and section C carrying 30 marks

2. Answer all questions in section A and B and two questions in section C

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

4. The following constants may be used:

Atomic mass , H=1, Cl=35.5, Cu=63.5, S=32, O=16, Ca=40, Na=23, C=12

-GMV at s.t.p=22.4dm³

-1Faraday=96,500C

-Standard pressure=760mmHg

-Standard temperature=273k

- 1 Litre=1dm 3=1000 cm3

SECTION “A”( 16 Marks)

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

i. A wasp sting is alkaline. The solution to help ease the pain by neutralizing the alkali would be one with a PH of:-

1. 5

2. 7

3. 8

4. 10

5. 13

ii. Five separate 1g samples of magnesium were placed in different beakers each containing 50cm cubes of dilute sulphuric acid. The mixture which showed the fastest reaction rate of the start was the one containing magnesium.

1. Block

2. Granules

3. Powder

4. Ribbon

5. Turnings

iii. Sea water contains various salts. Which salt is present in the greatest proportion

1. Magnesium chloride

2. Calcium sulphate

3. Potassium chloride

4. Sodium chloride

5. Magnesium sulphate

iv. The pair of elements which is most likely to form a covalent bond when reacted together is:-

1. Sodium and iodine

2. Magnesium and oxygen

3. Aluminium and oxygen

4. Carbon and Chlorine

5. Calcium and carbon

v. What number of faradays of electricity is required to deposit 4g of calcium from molten calcium chloride?

1. 0.1

2. 0.2

3. 0.8

4. 0.3

5. 0.7

vi. The electronic configuration of this element Cl^- is

1. 2:8:7

2. 2:8:8

3. 2:8:8:1

4. 2:8:8:1

5. 2:8:6

vii. In order to produce the greatest amount of hydrogen in a short time one gram of magnesium ribbon should react with

1. 10cm² of 0.5m Sulphuric acid

2. 40cm² of 0.5m Acetic acid solution

3. 40cm³ of 0.5m Sulphuric acid solution

4. 20cm³ of 1m sulphuric acid solution

5. 20cm³ of 1m acetic acid solution

viii. Which of the following substances represent a group of acid oxide?

1. Carbon dioxide, carbon monoxide and sulphur dioxide

2. Sulphur trioxide, nitrogen dioxide and nitrogen monoxide

3. Carbon dioxide, sulphur dioxide and dinitrogen oxide

4. Sulphur trioxide, carbon dioxide and nitrogen dioxide

ix. Bee sting can be cured by

1. NaOH

2. NH₄OH

3. HCl

4. NaHCO₃

5. Dilute HNO₃

x. Boiling removes water hardness because it causes;

1. Removal of ions

2. Calcium bicarbonate to dissolve

3. Calcium carbonate to precipitate

4. Formation of calcium bicarbonate

5. Removal of potassium ions

2. Choose the correct answer in list A with the response in list B

LIST A	LIST B
i. Potassium ii. Sodium iii. Calcium iv. Magnesium v. Zinc vi. Iron	Melts and burns with bright white flame Burns with a brick red flame Melts easily and burn with lilac flame Burns vigorously with a yellow flame Burn slowly with dull red flame Glows red hot Turns orange then surface of the product turns black

SECTION “B” ( 54 MARKS)

3. (a) M is a metal above hydrogen in the reactivity series and its oxide has the formula M₂O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context answer the following (i) What kind of combination exists between M and O?

2. How many electrons are there in the outermost shell of M?

3. Name the group to which M belongs?

4. State the reaction taking place at the cathode

5. Name the product at the anode

2. Give reasons for the following facts

   1. A cation is smaller than the atom from which it is formed. Why?

   2. An anion carries a negative charge. Why?

4. (a) Define the term molecular formula

   2. Briefly explain the following

1. Sacrificial protection

2. Why soda – an acid extinguisher containing sodium hydrogen carbonate knob (c) 1g of element T was completely converted to its chloride TCl₂ the mass of chloride formed was 3.96. calculate relative atomic mass of element T.

5. (a) A person suffering from indigestion produces 1.0 litres of gastric juice per day which contains about 2.00g of hydrochloric acid. How many ant acid tablets each contain 400Mg of sodium bicarbonate (NaHCO₃) are needed to neutralize all the hydrochloric acid produced in a day

(b) A mixture contained three colorless substances which were Alum, camphor and sugar. The solubility of these substances in different solvent is as follows

	Water	Ethanol	Ether
Alum	Soluble	Insoluble	Insoluble
Camphor	Insoluble	Soluble	Very soluble
Sugar	Soluble	Soluble	Insoluble

Use the information to answer the following questions.

1. What would be the quickest way to get some alum from the mixture?

2. How would you get a pure specimen of sugar from the mixture?

6. (a) A certain compound Q was heated and did not decompose. But when Q reacted with dilute hydrochloric acid gas P was produced the gas P turned lime water milky. When compound Q was burned in a direct flame it burned with golden – yellow flame.

1. Identify compound Q and gas P.

2. Write the balanced equation for the reaction between Q and dilute hydrochloric acid.

2. Two liquids A and B were mixed but after thoroughly shaking and allowing setting liquids floats.

1. What type of liquid does a mixture of A and B form

2. Which is the suitable apparatus that can be used to separate the two liquids?

2. i Why water is said to be universal solvent

ii.How can you test the presence of water in a substance?

6. (a) Iron is extracted in the blast furnace

1. Name the three raw materials fed at the top of blast furnace

2. Give one function of each raw material fed in the blast furnace

(b) (i) Write down three chemical equations that lead to the formation of iron in the blast furnace

(ii) At the bottom of the blast furnace two liquid are removed from different outers name the two liquids

6. (a) State le – principle

(b) In the industrial preparation of sulphur trioxide equilibrium is established between sulphur dioxide and oxygen gas as follow

2SO2(g) + O2(g) 2SO3(g) Δ H = - 94KJ/Mol

(c)How would you adjust temperature and pressure to maximize the proportion of the product at equilibrium

1. Why is it unfavorable to work with very high pressure and very low temperature in the contact process

2. What catalyst is used to speed up the rate of formation of sulphur trioxide before attaining the equilibrium?

SECTION “C” (30 Marks)

Answer only two questions

6. Lack of safe and clean water for industrial and domestic uses is a serious problem in most urban areas in Tanzania. The major cause of this problem is pollution in the water sources which cause the hardness of water. State six methods that could make such water clean and safe.

6. (a) In electrolytic production of hydrogen gas dilute mineral acid is used which method is used in its collection. Give reason

(b) If 0.2 faradays are used in production of hydrogen gas electrolytically then the gas formed is allowed to pass through a hot tube with a sample of copper (II) oxide and copper (II) sulphate.

1. In which chemical change and physical change occurred in the sample?

2. If the product for the chemical change involved one of its products was 10g of the solid and the other product was liquid. Calculate the volume of hydrogen gas that should be supplied and the volume of the hydrogen gas remained respectively to 0.2faraday at S.T.P

6. Three moles of sulphur dioxide gas combined with five males of oxygen gas to form sulphur trioxide gas in the contact process (i) Which reactant is present in smaller amount

(ii) Which reactant is present in large amount

(iii)Calculate the grams of the reactant left in the container (iv) How many moles of sulphur trioxide are produced?

(v) How many litres of sulphur trioxide are produced at S.T.P?

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