The organic compound which undergoes substitution reaction is:

1. C₂H₂
2. C₂H₄
3. C₁₀H₁₈
4. C₂H₆

Choose the correct answer from the options given : The electrolysis of acidified water is an example of :

1. Reduction
2. Oxidation
3. Redox reaction
4. Synthesis

The catalyst used in the Contact Process is:

1. Copper
2. Iron
3. Vanadium pentoxide
4. Manganese dioxide

Give one word or a phrase for the following statements:

(i) The energy released when an electron is added to a neutral gaseous isolated atom to form a negatively charged ion.

(ii) Process of formation of ions from molecules which are not in ionic state.

(iii) The tendency of an element to form chains of identical atoms.

(iv) The property by which certain hydrated salts, when left exposed to atmosphere, lose their water of crystallization and crumble into powder.

(v) The process by which sulphide ore is concentrated.