When potassium cyanide (KCN) reacts with acids, a deadly poisonous gas, hydrogen cyanide ( HCN ), is given off. Here is the equation:
$$
\mathrm{KCN}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{KCl}(a q)+\mathrm{HCN}(g)
$$
If a sample of 0.140 g of KCN is treated with an excess of HCl , calculate the amount of HCN formed, in grams.