Question

7.5 grams of a gas occupies 5.6 litres of volume at STP. The gas is

Answer 1

At STP, 
5.6 litres is occupied by 7.5g of a gas
Then, 
22.4 litres is occupied by
(22.4 × 7.5)/5.6 = 30 g of that gas 

(1 mole of every gas occupies around 22.4 l)

So, the molecular weight of the gas = 30g

The gas might be nitric oxide (NO)

because molar weight of NO = (N + O) = 14 + 16 = 30 g