Choose the conversion reaction which is exothermic & takes place by supply of catalytic energy.

1. Hydrogen to HCl
2. Ammonia to nitric acid
3. Nitrogen to nitric oxide
4. Oxygen to ozone.

Give a balanced equation for a direct combination reaction involving :

(a) Two elements — one of which is a neutral gas and the other a yellow non-metal

(b) Two elements – one of which is a neutral gas and the other a monovalent metal

(c) Two compounds – resulting in formation of a weak acid

Complete the statements by filling in the blank with the correct word/s :

1. Direct combination reaction of sulphur dioxide with water gives …………… [H₂SO₄/H₂SO₃/H₂S₂O₇].
2. Formation of hydrogen chloride from hydrogen and chlorine is an example of …………… [photochemical reaction / electrochemical reaction].
3. The reaction of hydrogen burning in oxygen to give a neutral liquid is an example of …………… [exothermic/endothermic] reaction.
4. The neutral gas evolved when lead nitrate undergoes thermal decomposition is …………… [nitrogen dioxide/oxygen/nitrogen].
5. The reddish brown precipitate obtained during a double decomposition - precipitation reaction between an iron salt and an alkali is …………… [iron [II] hydroxide / iron [III] hydroxide]

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

A : Ammonia
B : Hydrogen chloride
C : Hydrogen
D : Nitrogen dioxide
E : Nitric oxide

State the gaseous product formed, when -

1. An active metal reacts with dilute sulphuric acid.
2. A metallic nitrate undergoes thermal decomposition giving a coloured gas.
3. Two gases one of them neutral, combines by absorption of light energy.
4. An ammonium salt reacts with an alkali.
5. An exothermic reaction takes place between ammonia and a neutral gas.