Question

calculate the mass , volume and number of molecules of hydrogen gas liberated when 325gm of zinic react with excess hcl (zn = 65 u , h = 1u , cl = 35u)​

Answer 1

Answer:

Zn(s)+2HCl(aq)→ZnCl

2

(aq)+H

2

(g)

1 mole of Zn reacts with 2 moles of HCl to produce 1 mole of hydrogen.

The atomic mass of Zn is 65.4 g/mol. The molar mass of HCl is 36.5 g/mol.

When we divide mass with atomic/molar mass, we get number of moles.

Number of moles of Zn =

65.4

65

=0.994 moles.

Number of moles of HCl =

36.5

65

=1.78 moles.

0.994 moles of Zn will react with 2×0.994=1.988 moles of HCl however only 1.78 moles of HCl are present. Hence, HCl is the limiting reactant.

1.78 moles of HCl will produce

2

1.78

=0.89 moles of H

2

.

The molar mass of H

2

is 2 g/mol.

Mass of H

2

obtained =2g/mol×0.89mol=1.78g=1.8g