Question

Magnesium metal reacts with hydrochloric acid to produce magnesium chloride in solution and hydrogen gas. How many hydrogen molecules are produced when 60.0 g of magnesium is reacted in excess hydrochloric acid? Show step-by-step solution.

Answer 1

Solution:

The balanced chemical equation:

Mg(s) + 2HCl(aq) = MgCl₂(aq) + H₂(g)

According to the chemical equation: n(Mg) = n(H₂)

Moles of Mg = n(Mg) = Mass of Mg / Molar mass of Mg

The molar mass of Mg is 24.305 g/mol

n(Mg) = (60.0 g / 24.305 g/mol) = 2.4686 mol

n(Mg) = n(H₂) = 2.4686 mol

At STP, the volume of 1 mole of a gas contains 6.022×10²³ atoms or molecules of that gas.

So,

Number of molecules of H₂ = (2.4686 mol × 6.022×10²³) = 1.4866×10²⁴ = 1.49×10²⁴

Answer: 1.49×10²⁴ molecules of H₂ are produced.