Đặt \(n_{O_2}=x\left(mol\right)\)
\(2Cu\left(NO_3\right)_2\xrightarrow[]{t^o}2CuO+4NO_2\uparrow+O_2\\ \Rightarrow n_{NO_2}=4a\\ \Rightarrow22,4.\left(4a+a\right)=5,6\\ \Rightarrow a=0,05\left(mol\right)\\ \Rightarrow n_{Cu\left(NO_3\right)_2}=2a=0,1\left(mol\right)\\ \Rightarrow m_{Cu\left(NO_3\right)_2}=0,1.188=18,8\left(g\right)\)