When burning 96 kg of pyrite (a mineral containing FeS2), sulfur dioxide with a volume of 30.69 m3 was formed.

When burning 96 kg of pyrite (a mineral containing FeS2), sulfur dioxide with a volume of 30.69 m3 was formed. Calculate the mass fraction of non-combustible impurities in pyrite.

1) Let’s compose the equation of combustion of pyrite:
4FeS2 + 11O2 = 2Fe2O3 + 8SO2 ↑
2) Calculate the amount of sulfur dioxide substance:
n (SO2) = V (SO2) / Vm = 30.69 / 22.4 = 1.37 kmol.
3) Determine the mass of pure FeS2, the mass of impurities and their mass fraction in the original substance:
Let the amount of pyrite matter per 1.37 kmol of sulfur dioxide is x.
Then, according to the reaction equation, we compose the proportion:
x / 4 = 1.37 / 8
n (FeS2) = 0.685 kmol.
The mass of pure pyrite reacted is:
m (FeS2) = n (FeS2) ∙ M (FeS2) = 0.685 ∙ 120 = 82.2 kg.
the mass of impurities is:
m (impurities) = 99 – 82.2 = 13.8 kg
Mass fraction of impurities:
ω (impurities) = (m (impurities) ∙ 100) / m (pyrite) = 13.8 ∙ 100/96 = 14.375%
Answer: 14.375%.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.