How many liters of acetylene can be extracted from CaC2 with a mass of 8 g, containing 20% of impurities?

Given:
m (CaC2) = 8 g
ω approx. = 20%

To find:
V (C2H2) -?

Decision:
1) CaC2 + 2H2O => Ca (OH) 2 + C2H2;
2) ω (CaC2) = 100% – ω approx. = 100% – 20% = 80%;
3) m clean. (CaC2) = ω (CaC2) * m tech. (CaC2) / 100% = 80% * 8/100% = 6.4 g;
4) M (CaC2) = Mr (CaC2) = Ar (Ca) * N (Ca) + Ar (C) * N (C) = 40 * 1 + 12 * 2 = 64 g / mol;
5) n (CaC2) = m (CaC2) / M (CaC2) = 6.4 / 64 = 0.1 mol;
6) n (C2H2) = n (CaC2) = 0.1 mol;
7) V (C2H2) = n (C2H2) * Vm = 0.1 * 22.4 = 2.24 l.

Answer: The volume of C2H2 is 2.24 liters.