# For the reduction of 240 g of magnesium oxide, 80 g of coal were consumed: MgO + C = Mg

September 23, 2021 | education

| **For the reduction of 240 g of magnesium oxide, 80 g of coal were consumed: MgO + C = Mg + CO What is the mass fraction of pure carbon in this coal?**

1. Let’s write down the reaction equation:

MgO + C = Mg + CO.

2. Find the amount of magnesium oxide:

n (MgO) = m (MgO) / M (MgO) = 240 g / 40 g / mol = 6 mol.

3. Using the equation, we find the amount of pure coal and the mass:

np (C) = n (MgO) = 6 mol.

mh (C) = n (C) * M (C) = 6 mol * 12 g / mol = 72 g.

4. Let’s find the mass fraction of pure coal:

ω (C) = (mh (C) / mth (C)) * 100% = (72 g / 80 g) * 100% = 90%.

Answer: 90%.

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