Answer:
22.7%
Explanation:
We must first put down the equation of reaction to guide our work while solving the problem.
KCN(aq) + HCl (aq)--> KCl(aq) + HCN(aq)
The questions specifically state that HCl is in excess so KCN is the limiting reactant.
Number of moles of KCN reacted= mass of KCN reacted / molar mass of KCN
Mass of KCN reacted= 3.2 g
Molar mass of KCN= 65.12 g/mol
Number of moles of KCN= 3.2/65.12 g/mol= 0.049 moles
Theoretical yield of HCN is obtained thus;
From the reaction equation;
1 mol of KCN produced 1 mole of HCN thus 0.049 moles of KCN will produce 0.049 moles of HCN.
Mass of HCN = number of moles ×molar mass
Molar mass of HCN= 27.0253 g/mol
Hence mass of HCN produced= 0.049mol × 27.0253 g/mol= 1.32g of HCN
Actual yield of HCN= 0.30g
% yield= actual yield/ theoretical yield ×100
% yield= 0.30/1.32 ×100
%yield= 22.7%
