Identify one statement that does not hold true for electrorefining of copper:

1. Electrolyte is acidified CuSO₄ solution
2. Cathode is a thin strip of impure copper
3. Anode dissolves in the electrolyte
4. Anode gets thicker.

The observation when ammonium salt reacts with caustic soda:

1. A reddish brown gas
2. A colourless gas which gives dense white fumes with conc. HCI
3. A green coloured gas which turns moist blue litmus paper red.
4. A colourless gas which turns lime water milky.

Fused alumina is reduced to aluminium by electrolytic reduction, since:

1. alumina is highly stable.
2. alumina is least stable.
3. alumina is not reduced by drying agents.
4. alumina is not reduced by reducing agents.

Assertion (A): Addition reaction is a characteristic property of alkenes

Reason (R): Alkenes are double bond compounds.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.