Select the correct answer from A, B, C, D and E for each statement given below:

A: Hydrogen

B: Copper [II] oxide

C: Oxygen

D: Copper [II] hydroxide

E: Ammonia

1. The black residue obtained on heating copper carbonate.

2. The basic gas obtained when two gases react in presence of a catalyst and the reaction is exothermic.

3. The gas obtained when potassium chlorate is heated in the presence of a catalyst.

4. The pale blue precipitate obtained when copper [II] sulphate reacts with sodium hydroxide.

5. The gas which reacts with oxygen to give a neutral liquid.

Give a word equation for each of the following reactions.

1. Two solids which combine on heating, to give a liquid.

2. Two gasses which combine to give a solid.

3. A compound which on heating shows – color change from brown to yellow.

4. A salt which reacts with ammonium hydroxide to give a reddish-brown precipitate.

5. An exothermic reaction where both the reactants are gases, one of which is oxygen.

Give reasons for the following:

1. Even though rusting is an exothermic reaction, the heat evolved when an iron nail rusts are unnoticeable.

2. Electrolytic decomposition of water is a reaction involving a change of state.

3. A characteristic change of colour is seen when a piece of iron is added to copper [II] sulphate solution.

4. The catalytic oxidation of sulphur dioxide to sulphur trioxide is represented by a double arrow [⇌] between reactants and products, formed in the chemical reaction.

5. Silver salts are kept in dark coloured bottles.

Write word equations for the following chemical reactions given below. Also state the observation seen in each case.

1. ZnCO₃ $\xrightarrow{\Delta}$ ZnO + CO₂

2. NaCl + AgNO₃ ⟶ AgCl ↓ + NaNO₃

3. Na₂SO₃ + 2HCl $\xrightarrow{\Delta}$ 2NaCl + H₂O + SO₂

4. $2\text{SO}$2 + \text{O}2 \xrightleftharpoons [450\text{\degree C }]{\text{V}2\text{O}5} 2\text{SO}_3

5. Pb(NO₃)₂ + 2NH₄OH ⟶ 2NH₄NO₃ + Pb(OH)₂ ↓