Holy Child Public School

Chemistry Assignment
Class. X
Chapter Chemical reactions and equations
Multiple choice questions
1. Which of the following is(are) an endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
(a) (i) and (iii) (b) (ii) only
(c) (iii) only (d) (ii) and (iv)

2. In a chemical reaction between sodium sulphate and barium chloride solution the
white precipitates formed are of:
a. Hydrochloric acid
b. Barium sulphate
c. Chlorine
d. Sulphur

3. A chemical reaction does not involve:

a. Formation of new substances having entirely different properties than that of the
reactants
b. Breaking of old chemical bonds and formation of new chemical bonds
c. Rearrangement of the atoms of reactants to form new products
d. Changing of the atoms of on element into those of another element to form new
products

4. All the methods mentioned below can be used to prevent the food from getting
oxidised except:
i. Storing the food in the air-tight containers
ii. Storing the food in refrigerator
iii. Keeping the food in clean and covered containers
iv. Always touching the food with clean hands
a) (i) and (ii) b) (i) and (iii) c) (i), (iii) and (iv) d) (iii) and (iv)

5. The displacement reaction between iron (III) oxide and a metal X is used for welding
the rail tracks. Here X is:
a) Copper granules
b) Magnesium ribbon
c) Sodium pellets
d) Aluminium dust
 6. The neutralisation reaction between an acid and a base is a type of:
a) Double displacement reaction
b) Displacement reaction
c) Addition reaction
d) Decomposition reaction

7. The chemical reaction between Hydrogen sulphide and iodine to give Hydrogen
iodide and sulphur is given below:

The reducing and oxidising agents involved in this redox reaction are:
a) Iodine and sulphur respectively
b) Iodine and hydrogen sulphide respectively
c) Sulphur and iodine respectively
d) Hydrogen sulphide and sulphur

8. When ferrous sulphate is heated strongly it undergoes decomposition to form ferric

oxide as a main product accompanied by a change in colour from:
a) Blue to green.
b) Green to blue.
c) Green to brown.
d)Green to yellow

9. Chemically rust is
a) hydrated ferrous oxide
b) only ferric oxide
c) hydrated ferric oxide
d) none of these

10. The electrolytic decomposition of water gives H2 and O2 in the ratio of

a) 1 : 2 by volume
b) 2 : 1 by volume
c) 8 : 1 by mass
d) 1 : 2 by mass
11. Which of the following is a displacement reaction?

12. MnO2 + 4HCl → MnCl2+ 2H2O + Cl2

Identify the substance oxidised in the above equation.
a) MnCl2
b) HCl
c) H2O
d) MnO2
13. An element X on exposure to moist air turns reddish-brown and a new compound
Y is formed. The substances X and Y are
a) X = Fe, Y = Fe₂O₃
b) X = Ag, Y = Ag₂S
c) X = Cu, Y = CuO
d) X = Al, Y = Al₂O₃
14. Consider reaction is an example of
4NH₃ (g) + 5O₂ (g) → 4NO (g) + 6H₂O (g)
A). Displacement reaction,
B) Combination reaction
C) Redox reaction
D) Neutralization reaction.
a) (A) & (D)
b) (B) & (C)
c) (A) & (C)
d) (C) & (D)
Assertion Reason
Following questions consist of two statements – Assertion (A) and Reason (R).
Answer these questions selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
15. Assertion (A) : Calcium carbonate when heated gives calcium oxide and
water.
Reason (R) : On heating calcium carbonate, decomposition reaction takes
place.
16. Assertion (A) : Brown fumes are produced when lead nitrate is heated.
Reason (R) : Nitrogen dioxide gas is produced as a by product due to the
decomposition of lead nitrate.
17. Assertion (A): Pungent smelling gas is produced when sulphur burns in
air.
Reason (R) : Sulphur trioxide is formed on reaction of sulphur with oxygen.
18. Assertion (A) : In electrolysis of water, the volume of hydrogen liberated
is twice the volume of oxygen formed.
Reason (R) : Water (H,0) has hydrogen and oxygen in the ratio of 1:2 by
volume.
19. Assertion (A) : When HCl is added to zinc granules, a chemical reaction
occurs.
Reason (R) : Evolution of a gas and change in colour indicate that the
chemical reaction is taking place.

Subjective questions:
1. Differentiate the following chemical reactions as exothermic or endothermic in
nature?
(a) Decomposition of ferrous sulphate
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(d) Dissolution of ammonium chloride in water
2. Identify the oxidising and reducing agent in the following reactions:
(a) 4NH3 + 5O2 → 4NO + 6H2O
(b) Fe2O3 + 3CO → 2Fe + 3CO2
(c) 2H2 + O2 → 2H2O
3. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble
white substance is formed. Write the chemical reaction involved and also mention the
type of the chemical reaction?
4. Illustrate the following reactions in the form of balanced chemical equations:
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar
concentrations gives sodium chloride and sodium hydrogen carbonate.
(b) Sodium hydrogen carbonate on reaction with hydrochloric acid gives sodium
chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide,
liberates iodine gas and also forms potassium sulphate.
5. Explain why fireflies glow at night?
6. Grapes hanging on the plant do not ferment but after being plucked from the plant can
be fermented. Under what conditions do these grapes ferment? Is it a chemical or a
physical change?
7. Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot.
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
8. We store hydrogen peroxide in dark coloured bottles.Justify.
9. A silver article generally turns black when kept in the open for a few days. The article
when rubbed with toothpaste again starts shining.
(a) Why do silver articles turn black when kept in the open for a few days? Name the
phenomenon involved.
(b) Name the black substance formed and give its chemical formula.
10. On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide
(black), oxygen gas and a brown gas X is formed.
(a) Write a balanced chemical equation of the reaction.
(b) Identify the brown gas X evolved.
(c) Identify the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?
11. Give the characteristic tests for the following gases
(a) CO2 (b) SO2 (c) O2 (d) H2
12. Name the term used for the physical state of the solution of the reactant or product
dissolved in water.
13. Foods should be kept in air tight containers. Give a reason.
14. Name the gases released at cathode and anode during electrolysis of water.
15. All decomposition reactions are endothermic reactions. Explain why?
16. Give two examples of bio exothermic reactions.
17. Digestion of food is said to be endothermic or exothermic? Justify.
18. Mention the chemical equations involved in the following:
i) In white washing
ii) in black and white photography
iii) in cement industry
19. Explain the following terms and write an example for each
i) Precipitation reaction
ii) Neutralization reaction
20. Green coloured solution of ferrous sulphate fades,on addition of zinc granules.
Explain.

Case study

Corrosion is a dangerous and extremely costly problem. Because of it, buildings

and bridges can collapse, oil pipelines break, chemical plants leak, and bathrooms
flood. Corroded electrical contacts can cause fires and other problems, corroded
medical implants may lead to blood poisoning. The most common kind of
corrosion results from electrochemical reactions. General corrosion occurs when
most or all of the atoms on the same metal surface are oxidized, damaging the
entire surface.

(a) what is the name given to corrsion of iron. Write the chemical reaction
responsible for corrosion of iron .
b) How can we clean the tarnished copper vessels?
c) list the two ways to prevent corrosion of iron
d)Write the composition of Stainless steel.,state its importance.