a,\(CuO+2HCl\rightarrow CuCl_2+H_2\left(1\right)\)
b,
\(n_{CuO}=\frac{20}{80}=0,25\left(mol\right)\)
Theo PT (1) :
\(n_{HCl}=2n_{CuO}=0,25.2=0,5\left(mol\right)\)
\(n_{CuCl2}=n_{CuO}=0,25\left(mol\right)\)
\(\Rightarrow V_{HCl}=\frac{0,5}{2}=0,25\left(l\right)\)
\(\Rightarrow m_{CuCl2}=0,25.135=33,75\left(g\right)\)