Question

Fe + H2SO4 --> Fe2(SO4)3 + H2

Answer 1

I assume you have to balance the reaction?

a Fe + b H₂SO₄   →   c Fe₂(SO₄)₃ + d H₂

Count the number of times an element occurs on either side of the reaction. These numbers must be equal.

Fe: a = 2c

H: 2b = d

S: b = 3c

O: 4b = 12c

Two of these equations depend on c, so we can treat it as a free variable. Let c = 1. Then a = 2 (Fe) and b = 3 (S), from which it follows that d = 6 (H). So the balanced reaction is

2 Fe + 3 H₂SO₄   →   1 Fe₂(SO₄)₃ + 6 H₂