Question

The balanced chemical reaction: KCN(aq) + HCl(aq) ---> KCl(aq) = HCN(g)

If a sample of 0.140g of KCN is treated with an excess of HCl, calculate the amount of HCN formed, in grams.

**Please show work, I am trying to understand the math behind this for exams.

Answer 1

Mass of KCN reacted=0.140 g

Moles of KCN reacted=mass/molar mass of KCN=0.140g/65.12g mol^-1 =0.00215 moles

The coefficients of a reactant in a balanced chemical equation is the measure of the mole of the reactant taking part in the reaction.

1 mole KCN reacts with 1 mole HCl(though it is in excess) to form 1 mole of HCN

So, 0.00215 moles of KCN will form 0.00215 moles of HCN(1:1 ratio)

Mass of HCN formed=moles*molar mass of HCN=0.00215 moles*27.02 g/mol=0.0580g (Answer)