Vardaan Learning Institute

Topic: Chemical Reactions and Equations

Class: 10 (Science) Type: Bonus Practice Paper Max. Marks: 50
Name:
Date:
SECTION A: OBJECTIVE TYPE QUESTIONS (1 Mark Each)
1. Which of the following reactions involves the combination of two elements?
  1. $CaO + CO_2 \rightarrow CaCO_3$
  2. $4Na + O_2 \rightarrow 2Na_2O$
  3. $SO_2 + \frac{1}{2}O_2 \rightarrow SO_3$
  4. $NH_3 + HCl \rightarrow NH_4Cl$
2. When crystals of lead nitrate are heated strongly in a dry test tube:
  1. crystals immediately melt
  2. a brown residue is left
  3. white fumes appear in the tube
  4. a yellow residue is left
3. Which of the following is an endothermic reaction?
  1. Dilution of sulphuric acid
  2. Sublimation of dry ice
  3. Condensation of water vapours
  4. Respiration in human beings
4. Identify the reducing agent in the following reaction:
$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
  1. $Fe_2O_3$
  2. $CO$
  3. $Fe$
  4. $CO_2$
5. What happens when dilute hydrochloric acid is added to iron fillings?
  1. Hydrogen gas and iron chloride are produced.
  2. Chlorine gas and iron hydroxide are produced.
  3. No reaction takes place.
  4. Iron salt and water are produced.
6. Decomposition of vegetable matter into compost is an example of which type of reaction?
  1. Endothermic reaction
  2. Exothermic reaction
  3. Displacement reaction
  4. Decomposition reaction
7. Which of the following is effective in preventing rancidity?
  1. Adding antioxidants
  2. Storing food in air-tight containers
  3. Flushing with Nitrogen
  4. All of these
8. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is:
  1. 1:1
  2. 2:1
  3. 4:1
  4. 1:2
9. Which of the following gases can be used for storage of fresh sample of an oil for a long time?
  1. Carbon dioxide or oxygen
  2. Nitrogen or oxygen
  3. Carbon dioxide or helium
  4. Helium or nitrogen
10. One of the following does not happen during a chemical reaction. This is:
  1. Breaking of old chemical bonds and formation of new chemical bonds
  2. Formation of new substances with entirely different properties
  3. Atoms of one element change into those of another element to form new products
  4. A rearrangement of atoms takes place to form new products
Directions (Q11-Q14): In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
11. Assertion (A): White silver chloride turns grey in sunlight.
Reason (R): Decomposition of silver chloride in presence of sunlight takes place to form silver metal and chlorine gas.
12. Assertion (A): Burning of Magnesium ribbon is a physical change.
Reason (R): Burning of Magnesium ribbon forms Magnesium Oxide which is a new substance.
13. Assertion (A): In a reaction of copper with oxygen, copper serves as a reducing agent.
Reason (R): The substance which gains oxygen in a chemical reaction is a reducing agent.
14. Assertion (A): Chemical equation is balanced to satisfy the law of conservation of mass.
Reason (R): The total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants.
SECTION B: SHORT ANSWER QUESTIONS (3 Marks Each)
15. Balance the following chemical equations:
  1. $HNO_3 + Ca(OH)_2 \rightarrow Ca(NO_3)_2 + H_2O$
  2. $NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O$
  3. $NaCl + AgNO_3 \rightarrow AgCl + NaNO_3$
16. A solution of a substance 'X' is used for whitewashing.
(i) Name the substance 'X' and write its formula.
(ii) Write the reaction of the substance 'X' named in (i) above with water.
(iii) Why does the wall shine after 2-3 days of whitewashing?
17. Why does the colour of copper sulphate solution change when an iron nail is dipped in it? Write the balanced chemical reaction involved. Identify the type of reaction.
18. What is a precipitation reaction? Give an example. Explain how it is different from a double displacement reaction which is not a precipitation reaction.
19. Write the balanced chemical equations for the following reactions:
(a) Calcium hydroxide + Carbon dioxide $\rightarrow$ Calcium carbonate + Water
(b) Zinc + Silver nitrate $\rightarrow$ Zinc nitrate + Silver
(c) Aluminium + Copper chloride $\rightarrow$ Aluminium chloride + Copper
20. Explain redox reaction with an example. Identify the substance oxidized and reduced in the reaction:
$MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2$
SECTION C: LONG ANSWER QUESTIONS (5 Marks Each)
21. (i) Define corrosion. What are the conditions necessary for the corrosion of iron?
(ii) Name the protective method used to prevent corrosion of:
(a) Iron railing
(b) Iron pans
(iii) Write the chemical formula of rust.
(iv) Explain the term 'Rancidity'. Name two antioxidants.
22. Identify the type of chemical reaction taking place in each of the following:
(a) Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.
(b) On heating copper powder in air in a china dish, the surface of copper powder turns black.
(c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphur is experienced.
(d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.
(e) Quick lime reacts vigorously with water releasing a large amount of heat.
SECTION D: CASE STUDY (4 Marks)
23. Read the following text and answer the questions:
A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products. The properties of the products are different from those of the reactants.

During a chemistry lab experiment, a teacher demonstrated a reaction by taking a small amount of calcium oxide or quick lime in a beaker and slowly added water to it.

(i) Which type of reaction is demonstrated by the teacher? (1 Mark)
(ii) Is energy released or absorbed in this reaction? (1 Mark)
(iii) Write the balanced chemical equation for the reaction. (2 Marks)
24. Read the following text and answer the questions:
Corrosion is the phenomenon of deterioration of surface of metal by the action of air and moisture. It is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually a metal) by chemical and/or electrochemical reaction with their environment.

(i) What is the chemical name and formula of rust? (1 Mark)
(ii) Which two conditions are necessary for the rusting of iron? (1 Mark)
(iii) Suggest any two methods to prevent corrosion of iron. (2 Marks)
"All the best!"