\(PTHH:C_2H_5OH+3O_2\rightarrow^{t^o}2CO_2+3H_2O\\ m_{C_2H_5OH}=115\cdot0,8=92\left(g\right)\\ \Rightarrow n_{C_2H_5OH}=\dfrac{92}{46}=2\left(mol\right)\\ \Rightarrow n_{O_2}=6\left(mol\right)\\ \Rightarrow V_{O_2}=6\cdot22,4=134,4\left(l\right)\\ \Rightarrow V_{kk}=\dfrac{134,4\cdot100\%}{20\%}=672\left(l\right)\)