Chemical Reactions and Equations

Q.1. What is the general name of substances which are added to fat & oil containing
food to prevent rancidity. (1 Mark)

Ans. Antioxidants

Q.2. Write balanced chemical equation for the reaction of barium chloride with
Aluminium sulphate. (1 Mark)

Ans. 3 BaCl2 + Al2­ (SO4)3 3 BaSO4 +2AlCl3.

Q.3. Identify the substance that is oxidised and the substance that is reduced in the
following reaction. 4 Na+O2 2 Na2O (1 Mark)

Ans. Substance Oxidised Na
Substance reduced O2

Q.4. Why does the colour of copper sulphate solution fade when iron nail is dipped in
it. (2 Mark)
Ans. The solution changes into iron sulphate Fe+CuSO4 FeSO4 + Cu

Q.5. What happens when quick lime is added to water? Write the chemical equation.
Which type of reaction is it endothermic or exothermic? (2 Mark)
Ans. Calcium oxide reacts vigorously with water to produce slaked lime (Calciumm hydroxide)
CaO+H2O Ca (OH)2­ +Heat energy. It is an exothermic reaction.

Q.6. Silver chloride turns grey when kept in sunlight. Write