When magnesium burns in air, the atoms of the metal reacts with the oxygen gas to produce magnesium oxide.

Which of the following is correct?

P. It is a combination reaction.

Q. It is a Redox reaction

R. It is a decomposition reaction

1. Only P
2. Only Q
3. Only R
4. Both Q and R

Which of the following is NOT correct about electro-refining of copper?

1. Cathode is pure copper rod and anode is impure copper block.
2. Cathode is impure copper block and anode is pure copper rod.
3. Electrolyte is copper sulphate solution, acidified with sulphuric acid.
4. Anode mud may contain silver and gold as insoluble impurities.

A reactive metal (P) is treated with H₂SO₄ (dil). The gas is evolved and is collected over water. Which of the following conclusion is correct

P. The gas is hydrogen

Q. The gas is lighter than air

1. Only P
2. Only Q
3. Both P and Q
4. Neither P nor Q

In which of the following solution, Zn can displace metal from the solution?

1. P
2. Q
3. R
4. S