The mixture contains calcium carbonate and magnesium carbonate. Calculate the mass fraction of calcium carbonate if the amount of the substance is 0.3 mol, and the amount of magnesium carbonate is 0.25 mol?
n (CaCO3) = 0.3 mol
n (MgCO3) = 0.25 mol
ω (CaCO3) -?
1) M (CaCO3) = Mr (CaCO3) = Ar (Ca) * N (Ca) + Ar (C) * N (C) + Ar (O) * N (O) = 40 * 1 + 12 * 1 + 16 * 3 = 100 g / mol;
2) m (CaCO3) = n (CaCO3) * M (CaCO3) = 0.3 * 100 = 30 g;
3) M (MgCO3) = Mr (MgCO3) = Ar (Mg) * N (Mg) + Ar (C) * N (C) + Ar (O) * N (O) = 24 * 1 + 12 * 1 + 16 * 3 = 84 g / mol;
4) m (MgCO3) = n (MgCO3) * M (MgCO3) = 0.25 * 84 = 21 g;
5) m mixture = m (CaCO3) + m (MgCO3) = 30 + 21 = 51 g;
6) ω (CaCO3) = m (CaCO3) * 100% / m mixture = 30 * 100% / 51 = 58.82%.
Answer: The mass fraction of CaCO3 is 58.82%.
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