Zn (s) + 2HCl (aq) - >ZnCl2 (aq) + H2 (g)

Which statement is true at STP? (The atomic mass of Zn is 65.39 u.)

2 mol of HCl produce 1 L of H2 gas.

1 L of Zn produces 1L of H2 gas.

65.39 g of Zn produce 22.4 L of H2 gas.

1 L of HCl produces 1 mol of H2 gas.

To answer this we need to assume that at STP 1 mol of a substance is equal to 22.4 L. We use this data for the calculations.

Statement 1

2 mol HCl (1 mol H2 / 2 mol HCl) = 1 mol H2 thus at STP 22.4 L H2

This statement is false.

Statement 2

1 L Zn (1 mol Zn / 22.4 L Zn) (1 mol H2 / 1 mol Zn) (22.4 L H2 / 1 mol H2) = 1L H2

This statement is true.

Statement 3

65.39 g Zn (1 mol Zn / 65.39 g Zn) (1 mol H2 / 1 mol Zn) = 1 mol H2

This statement is true.

Statement 4

1L HCl (1 mol HCl / 22.4 L HCl) (1 mol H2 / 2 mol HCl) = 0.022 mol H2

This statement is false.