Given that the relative molecular mass of copper oxide is 80, what volume of ammonia (measured at STP) is required to completely reduce 120 g of copper oxide? The equation for the reaction is:
3CuO + 2NH3 ⟶ 3Cu + 3H2O + N2
3CuO+2NH33 mol.2 mol.=3×80 g.=2×22.4 lit.=240 g.=44.8 lit.\begin{matrix} 3\text{CuO} & + & 2\text{NH}_3 \\ 3\text{ mol.} & & 2 \text{ mol.} \\ = 3 \times 80 \text{ g.} & & = 2 \times 22.4 \text{ lit.} \\ = 240 \text{ g.} & & = 44.8\text{ lit.} \\ \end{matrix}3CuO3 mol.=3×80 g.=240 g.+2NH32 mol.=2×22.4 lit.=44.8 lit.
⟶3Cu+3H2O+N2\longrightarrow 3\text{Cu} + 3\text{H}_2\text{O} + \text{N}_2⟶3Cu+3H2O+N2
240 g of CuO is reduced by 44.8 lit of NH3
∴ 120 g of CuO is reduced by 44.8240\dfrac{44.8}{240}24044.8 x 120 = 22.4 lit.
Hence, 22.4 lit of NH3 is required