Question

Zn + HCl → ZnCl₂+ H₂ 

Calculate amount of zinc required to release 500g of hydrogen. (Zn = 65 U, H = 1 U, Cl = 35.5 U are the atomic masses).

Answer 1

The balanced chemical equation is 

Zn + 2 HCl → ZnCl₂ + H₂ 65 U + (2 × 36.5) U → (65 + 2 × 35.5) U + 2 U 65 g + 73 g → 136 g + 2g 

As per the balanced equation 65 g Zinc is reacting with hydrochloric acid to produce 2g of Hydrogen.

So the amount of Zinc required to produce 500 g hydrogen = 65/2 x500 = 16250 g.