Calcium oxide weighing 5.6 g was mixed with carbon weighing 5.4 g.

Calcium oxide weighing 5.6 g was mixed with carbon weighing 5.4 g. The mixture was heated. determine the composition of the mixture after the reaction.

Given:
m (CaO) = 5.6 g
m (C) = 5.4 g

To find:
mixture -?

Decision:
1) CaO + 3C => CaC2 + CO;
2) n (CaO) = m (CaO) / M (CaO) = 5.6 / 56 = 0.1 mol;
3) n (C) = m (C) / M (C) = 5.4 / 12 = 0.45 mol;
4) n (CaC2) = n (CaO) = 0.1 mol;
5) m (CaC2) = n (CaC2) * M (CaC2) = 0.1 * 64 = 6.4 g;
6) n react. (C) = n (CaO) * 3 = 0.1 * 3 = 0.3 mol;
7) n rest. (C) = n (C) – n reag. (C) = 0.45-0.3 = 0.15 mol;
8) m rest. (C) = n rest. (C) * M (C) = 0.15 * 12 = 1.8 g.

Answer: The mass of CaC2 is 6.4 g; the remaining C – 1.8 g.