5. If 6.5 g of magnesium ribbon reacts completely
with hydrochloric acid, how many grams of
hydrogen gas would be liberated? Mg , + 2HC1(ag)
→ MgC1 + H, [H = 1.0, Mg = 24.0]

The mass of hydrogen gas liberated is 0.6 g.

Explanation:

Given data:

Mass of Mg = 6.5 g

Mass of hydrogen gas liberated = ?

Solution:

Chemical equation:

Mg + 2HCl     →    MgCl₂ + H₂

Now we will calculate the number of moles of Mg.

Number of moles = mass / molar mass

Number of moles = 6.5 g/ 24 g/mol

Number of moles = 0.3 mol

Now we will compare the moles of Mg with hydrogen gas.

            Mg         :          H₂

             1           :           1

             0.3       :        0.3

Mass of H₂:

Mass = number of moles × molar mass

Mass = 0.3 mol × 2 g/mol

Mass = 0.6 g