Calculate how much silicon oxide (4) can be reduced with 40 kg carbon if the mass fraction of impurities in the coke is 10 percent.

1. Let’s compose the equation of the chemical reaction:

SiO2 + 2C = Si + 2CO.

2. Find the chemical amount of carbon:

40 kg = 40,000 g.

ω (C) = 100% – ω (impurities) = 100% – 10% = 90%.

m (C) = m (mixture) * ω (C) / 100% = 40,000 g * 90% / 100% = 36,000 g.

n (C) = m (C) / M (C) = 36000 g / 12 g / mol = 3000 mol.

3. According to the reaction equation, we find the chemical amount, and then the mass of silicon oxide:

n (SiO2) = n (C) / 2 = 3000 mol / 2 = 1500 mol.

m (SiO2) = n (SiO2) * M (SiO2) = 1500 mol * 60 g / mol = 90000 g = 90 kg.

Answer: m (SiO2) = 90 kg.