Khí thoát ra : Metan
\(C_2H_2 + 2Br_2 \to C_2H_2Br_4\)
\(\%V_{CH_4} = \dfrac{3,36}{8,96}.100\% = 37,5\%\\ \%V_{C_2H_2} = 100\% - 37,5\% = 62,5\%\)
\(n_{C_2H_2} = \dfrac{8,96.62,5\%}{22,4} = 0,25(mol)\\ Ca_2C_2 + 2H_2O \to Ca(OH)_2 + C_2H_2\\ n_{Ca_2C_2} = n_{C_2H_2} = 0,25(mol)\\ \Rightarrow m_{đất\ đèn} = \dfrac{0,25.104}{80\%} = 32,5\ gam\)