Question

If 2.00 g of Mg reacts completely with 50.0 mL of HCl solution as shown in the following reaction, what is the molarity of the HCl solution?

Answer 1

Answer:

Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(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 =65.465=0.994 moles.

Number of moles of HCl =36.565=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 21.78=0.89 moles of H2.

The molar mass of H2 is 2 g/mol.

Mass of H2 obtained =2g/mol×0.89mol=1.78g=1.8g