$n_{H_2}=6,72/22,4=0,3mol$
$PTPU :$
$2Al+3H_2SO_4\to Al_2(SO_4)_3+3H_2↑$
Theo pt :
$n_{Al}=2/3.n_{H_2}=2/3.0,3=0,2mol$
$⇒x=m_{Al}=0,2.27=5,4g$
Theo pt :
$n_{H_2SO_4}=n_{H_2}=0,3mol$
$⇒V_{H_2SO_4}=\dfrac{0,3}{1}=0,3l$
Theo pt :
$n_{Al_2(SO_4)_3}=1/3.n_{H_2}=1/2.0,3=0,1mol$
$⇒C_{M_{Al_2(SO_4)_3}}=\dfrac{0,1}{0,3}≈0,33M$