During the decomposition of magnesium carbonate, carbon dioxide was released, which was passed through lime water.

During the decomposition of magnesium carbonate, carbon dioxide was released, which was passed through lime water. This formed a precipitate weighing 2.5 g. Calculate the mass of magnesium carbanate.

MgCO3 = MgO + CO2.

Ca (OH) 2 + CO2 = CaCO3 ↓ + H2O.

Let’s find the amount of substance CaCO3.

n = m: M.

M (CaCO3) = 100 g / mol.

n = 2.5 g: 100 g / mol = 0.025 mol.

Let’s find the quantitative ratios of substances.

For 1 mol of CaCO3, there is 1 mol of CO2.

Substances are in quantitative ratios 1: 1.

The amount of CO2 and the amount of CaCO3 are equal.

n (CO2) = n (CaCO3) = 0.025 mol.

n (CO2) = n (MgCO3) = 0.2 mol.

Let’s find the mass of MgCO3.

M (MgCO3) = 84 g / mol.

m = 84 g / mol × 0.025 mol = 2.1 g.

Answer: 2.1 g.