(i) A gas of mass 32 gms has a volume of 20 litres at S.T.P. Calculate the gram molecular weight of the gas.
(ii) How much Calcium oxide is formed when 82 g of calcium nitrate is heated? Also find the volume of nitrogen dioxide evolved:
2Ca(NO3)2 ⟶ 2CaO + 4NO2 + O2
[Ca = 40, N = 14, O = 16]
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(i) 20 lit. of gas weighs = 32 g.
1 mole = 22.4 lit. of gas will weigh = $\frac{32}{20}$ x 22.4 = 35.84 g.
Hence, gram mol. weight of the gas = 35.84 g.
(ii)
$$\begin{matrix} 2\text{Ca}(\text{NO}_3)_2 & \longrightarrow & 2\text{CaO} & + & 4\text{NO}_2 & + & \text{O}_2 \\ 2[(40) + & & 2(40 & & 4[22.4] \\ 2(14 +3(16))] & & + 16) & & \text{ lit.} \\ = 328 \text{ g} & & 112 \text{g} \\ \end{matrix}$$
(a) 328 g of Ca(NO3)2 produces 112 g of calcium oxide.
∴ 82 g of Ca(NO3)2 will produce = $\frac{112}{328}$ x 82 = 27.99 g = 28 g
Hence, 28 g of calcium oxide is produced.
(b) 328 g of Ca(NO3)2 produces 4(22.4) lit of nitrogen dioxide.
∴ 82 g of Ca(NO3)2 will produce = $\frac{4 \times 22.4}{328}$ x 82 = 22.4 lit.
Hence, vol of nitrogen dioxide evolved = 22.4 lit.