Chemical Reactions and Equations
1. Which of the following statement about the reaction below are incorrect?
2PbO (s) + C (s) → 2Pb (s) + CO2 (g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidized
(c) Lead oxide is getting oxidized
(d) Lead is getting reduced
i. (a) and (b)
ii. (a) and (c)
iii. (a), (b) and (c)
2. Fe203 + 2A1 → Al203 + 2Fe
The above reaction is an example of a
(a) Combination reaction
(b) Double displacement reaction
(c) Decomposition reaction
(d) Displacement reaction
3. What happens when dilute hydrochloric acid is added to iron filling? Tick the correct answer
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced
(c) No reaction takes place
(d) Iron salt and water are produced.
4. What is balanced chemical equation? Why should chemical equation be balanced?
5. Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and Sulpher dioxide.
(c) Barium chloride reacts with aluminum sulphate to give aluminum chloride and precipitate of barium sulphate
6. Balance the following chemical equations:
(a) HNO3 + Ca(OH)2 → Ca(OH)2 → Ca(NO3)2 +H20
(b) NaOH +H2SO4 → Na2SO4 + H20
(C) NaCl+AgNO3 → AgCl + NaNO3
(d) BaCl2 +H2SO4 → BaSO4 +HCl
7. Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminum + Copper chloride → Aluminum chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + potassium chloride
8. Write the balanced chemical equation for the following and identify the type of reaction in each case.
Potassium bromide (s) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide(s)
Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)
Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)
Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)
9. What does one mean by exothermic and endothermic reactions? Give examples.
10. Why respiration is considered an exothermic reaction? Explain.
11. Why decomposition reactions are called the opposite of combination reactions? Write equations for these reactions.
12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
13. What is difference between displacement and double displacement reactions? Write equations for these reactions.
14. In refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
15. What do you mean by a precipitation reaction? Explain by giving examples.
16. Explain the following in terms of gain and loss of oxygen with two examples each?
17. A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element `X’ and the black coloured compound formed.
18. Why do we apply paint on iron articles?
19. Oil and fat containing food items are flushed with nitrogen. Why?
20. Explain the following terms with one example each.
21. Why should a magnesium ribbon be cleaned before burning in air?
22. Write the balance equation for the following reactions Give reasons for the following reactions?
i. Hydrogen + Chlorine → Hydrogen chloride
ii. Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
iii. Sodium + water → Sodium hydroxide + water
23. Write the balanced chemical equation with state symbols for the following reactions?
i. Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and solution of sodium chloride.
ii. Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
24. A solution of a substance ‘X’ is used for white washing
i. Name the substance `X’ and writes its formula.
ii. Write the reaction of the substance `X’ named in (i) above with water
25. Why the amount of gas collected in one of the tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
26. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
27. Give an example of a double displacement reaction other than the one given in Activity 1.10.
28. Identify the substances that are oxidized and the substances that are reduced in the following reactions.
i. 4Na (s) + 02 (g) → 2Na20 (s)
ii. CuO (s) + H2 → Cu (s) + H2O (l)