Răspuns :
2Al + 3H₂SO₄ ⇒ Al₂(SO₄)₃ + 3H₂
MAl=27g/mol
MH₂=2AH=2*1=2g/mol
n=m/M=135/27=5 moli Al
2 moli Al..........................3 moli H₂
5 moli Al..........................x moli H₂
x=3*5/2=7,5 moli H₂
n=m/M=>m=n*M=7,5*2=15g H₂
MAl=27g/mol
MH₂=2AH=2*1=2g/mol
n=m/M=135/27=5 moli Al
2 moli Al..........................3 moli H₂
5 moli Al..........................x moli H₂
x=3*5/2=7,5 moli H₂
n=m/M=>m=n*M=7,5*2=15g H₂
Reactia este: 2Al+3H2SO4=Al2(SO4)3+3H2
Apoi dintr-un tabel/sistem periodic stim ca nr. de masa A este: A aluminiu =27 si A hidrogen=1
Deci un mol Al are 27 g, iar un mol H2 are 2 g
Se construiește regula de trei simpla dupa reactia scrisa mai sus:
2*27g Al..................3*2g H2
135g Al.....................x g H2
x=(135*3*2):(2*27)=15
R: 15 g H2