Al(s) + H2SO4(aq) → Al2(SO4)3(aq) + H2(g)

Question

What is the coefficient of H2 in the balanced equation, obtained by using oxidation numbers?

Answer 1

2Al(s) + H2SO4(aq) → Al2(SO4)3(aq) + H2(g)
..0x2 = 0..2*1+ = 2.........2*3+ = 6..............0
multiply Al half by 1 and multiply H2SO4/H2 half by 3 to give

2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g)