$n_{Al}=10,8/27=0,4mol$
$a/2Al+3H_2SO_4\to Al_2(SO_4)_3+3H_2↑$
b/Theo pt :
$n_{H_2}=3/2.n_{Al}=3/2.0,4=0,6mol$
$⇒V_{H_2}=0,6.22,4=13,44l$
$c/m_{ddspu}=10,8+200-0,6.2=209,6g$
Theo pt :
$n_{Al_2(SO_4)_3}=1/2.n_{Al}=1/2.0,4=0,2mol$
$⇒m_{Al_2(SO_4)_3}=0,2.342=68,4g$
$⇒C\%_{Al_2(SO_4)_3}=\dfrac{68,4}{209,6}.100\%=32,63\%$