Question

___1___Zn + __2___HCl → ___1___H2 + ____1__ZnCl2

How many grams of hydrogen gas form when 102 grams of hydrochloric acid reacts with 128 grams of zinc?

Answer 1

Mass = 2.8 g

Step-by-step explanation:

Given data:

Mass of HCl = 102 g

Mass of Zn = 128 g

Mass of H₂ = ?

Solution:

Chemical equation:

2HCl + Zn → H₂ + ZnCl₂

Number of moles of Zn:

Number of moles = mass/molar mass

Number of moles = 128 g/ 65.38 g/mol

Number of moles = 2 mol

Number of moles of HCl:

Number of moles = mass/molar mass

Number of moles = 102 g/ 36.5 g/mol

Number of moles = 2.8 mol

Now we will compare the moles of hydrogen gas with HCl and Zn.

HCl : H₂

2 : 1

2.8 : 1/2×2.8 = 1.4 mol

Zn : H₂

1 : 1

2 : 2

Number of moles of hydrogen formed by HCl are less thus it will limiting reactant.

Mass of Hydrogen:

Mass = number of moles × molar mass

Mass = 1.4 mol × 2 g/mol

Mass = 2.8 g