# Determine the mass fraction of hydrochloric acid added to 5.6 g of magnesium sulfide. The mass of the hydrochloric

Determine the mass fraction of hydrochloric acid added to 5.6 g of magnesium sulfide. The mass of the hydrochloric acid solution is 116.8 g.

Reaction equation: 2HCl + MgS = MgCl2 + H2S
Let’s find the amount of magnesium sulfide substance n = 5.6 g / 56 g / mol = 0.1 mol. By reaction with 2 mol of hydrochloric acid, 1 mol of magnesium sulfide reacts, n (HCl) / 2 = 0.1 / 1. n (HCl) = 2 * 0.1 = 0.2 mol. Then the mass of the hydrochloric acid substance is m = n * M = 0.2 mol * 36.5 g / mol = 7.3 g. Mass fraction of the acid w = mv-va / mr-pa = 7.3 g / 116.8 g = 0.0625 or 6.25%. (M is the molar mass determined by the periodic table).
Answer: the mass fraction of hydrochloric acid is 6.25%.

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