\(n_{SO_3}=\dfrac{8}{80}=0.1\left(mol\right)\)
\(SO_3+H_2O\rightarrow H_2SO_4\)
\(0.1......................0.1\)
\(C_{M_{H_2SO_4}}=\dfrac{0.1}{0.5}=0.2\left(M\right)\)
\(n_{CuO}=\dfrac{10}{80}=0.125\left(mol\right)\)
\(CuO+H_2SO_4\rightarrow CuSO_4+H_2O\)
\(0.1...........0.1\)
\(m_{CuO\left(dư\right)}=\left(0.125-0.1\right)\cdot80=2\left(g\right)\)