**(i)** Calculation:

Moles of oxygen = 1.6/32

Moles of oxygen = 0.05mol

1 mol of oxygen= 22.4L (at STP)

Volume of Oxygen (V1) = 22.4 × 0.05

Volume of Oxygen (V1) = 1.12L

V2 =?

P1 = 1atm

P2 = ½

P2 = 0.5atm

According to the Boyle’s law,

P1V1 = P2V2

V2 = 1 × 1.12/0.5

Hence, V2 = 2.24L

**(ii)** Calculation:

The number of molecules in 1.6g / 0.005mol = 6.022 × 1023 × 0.05

The number of molecules in 1.6g / 0.005mol = 3.011 × 10^{22}