Question

Students in a chemistry class added 5 g of Zinc (Zn) to 50 g of hydrochloric acid (HCl). A chemical reaction occurred that produced zinc chloride (ZnCl2) and 6 g of hydrogen gas (H2).
Zn+ 2HCl → ZnCl2+H2

What is the mass of the zinc chloride?

Answer 1

Answer: 11 g

Explanation:

Zn + 2HCl    →   ZnCl₂ + H₂

Number of moles of Zn:

Number of moles = 5 g / 65.38 g/mol

Number of moles = 0.08 mol

Number of moles of HCl :  

Number of moles = 50 g / 36.5 g/mol

Number of moles = 1.4 mol

Compare the moles of both reactant with zinc chloride:

             Zn             :           ZnCl₂

              1             :             1

             0.08       :        0.08

           HCl          :         ZnCl₂

             2            :           1

            1.4          :         1/2×1.4 =0.7 mol

The number of moles of zinc chloride produced by Zn are less so it will limit reactants.

Mass of zinc chloride:

Mass = 0.08 mol × 136.3 g/mol

Mass = 11 g