\(n_{N_2}=\dfrac{1.12}{22.4}=0.05\left(mol\right)\)
\(n_{CO_2}=\dfrac{8.8}{44}=0.2\left(mol\right)\)
\(n_{H_2O}=\dfrac{4.5}{18}=0.25\left(mol\right)\)
\(m_O=7.5-0.05\cdot2\cdot14-0.2\cdot12-0.25\cdot2=3.2\left(g\right)\)
\(n_O=0.2\left(mol\right)\)
\(CT:C_xH_yO_zN_t\)
\(x:y:z:t=0.2:0.5:0.2:0.1=2:5:2:1\)
\(CT:C_2H_5ON\)