\(n_{AgCl}=\dfrac{43.05}{143.5}=0.3\left(mol\right)\) \(\Rightarrow n_{HCl}=0.3\left(mol\right)\)
\(n_{HCl}=\dfrac{6.72}{22.4}=0.3\left(mol\right),n_{Cl_2}=\dfrac{4.48}{22.4}=0.2\left(mol\right)\)
\(H_2+Cl_2\underrightarrow{^{^{t^0}}}2HCl\)
\(0.15....0.15.......0.3\)
\(H\%=\dfrac{0.15}{0.2}\cdot100\%=75\%\)