a: \(CuCl_2+2KOH\rightarrow Cu\left(OH\right)_2\downarrow+2KCl\)
b: \(n_{CuCl_2}=\dfrac{54}{135}=0.4\left(mol\right)\)
=>\(n_{Cu\left(OH\right)_2}=0.4\left(mol\right)\)
\(m_{Cu\left(OH\right)_2}=0.4\cdot\left(64+16\cdot2+2\right)=39.2\left(g\right)\)