56.0 L of nitrogen gas is mixed with excess hydrogen gas and it is found that 20 L of ammonia gas is produced. The volume of unused nitrogen gas is found to be _________ L.

A sample of 4.5 mg of an unknown monohydric alcohol, R-OH was added to methylmagnesium iodide. A gas is evolved and is collected and its volume measured to be 3.1 mL. The molecular weight of the unknown alcohol is __________ g/mol. [Nearest integer]

Blister copper is produced by reaction of copper oxide with copper sulphide.

2Cu₂O + Cu₂S $$\to$$ 6Cu + SO₂

When 2.86 $$\times$$ 10³ g of Cu₂O and 4.77 $$\times$$ 10³ g of Cu₂S are used for reaction, the mass of copper produced is _____________ g. (nearest integer)

(Atomic mass of Cu = 63.5 a.m. u, S = 32.0 a.m. u, O = 16.0 a.m. u)

The complete combustion of 0.492 g of an organic compound containing 'C', 'H' and 'O' gives 0.793 g of CO₂ and 0.442 g of H₂O. The percentage of oxygen composition in the organic compound is ______________. (nearest integer)