$(1)$ Weight of $H _{2}=$ mole $\times$ molecular weight

$=0.2 \times 2$

$=0.4\, g$

$(2)$ $6.023 \times 10^{23}= 1 \,mol$

$6.023 \times 10^{22}= 0.1 \,mol$

The weight of Nitrogen,

$N _{2}=0.1 \times 28=2.8 \,g$

$(3)$ Weight of silver is $0.1 \,g$

$(4)$ Weight of oxygen $=32 \times 0.1=3.2\, g$