$n_{CH_4}=17,92/22,4=0,8mol$
$a/CH_4+2O_2\overset{t^o}\to CO_2+2H_2O$
b/Theo pt :
$n_{H_2O}=2.n_{CH_4}=2.0,8=1,6mol$
$⇒m_{H_2O}=1,6.18=28,8g$
$c/n_{CO_2}=n_{CH_4}=0,8mol$
$⇒V_{CO_2}=0,8.22,4=17,92l$
$n_{O_2}=2.n_{CH_4}=2.0,8=1,6mol$
$⇒V_{kk}=1,6.22,4.5=179,2l$