Question

Covellite is a soft, indigo-blue mineral in which the copper to sulfur ratio by mass is 1.00 g of S to 0.506 g of Cu. Chalococite is a soft, black mineral in which the copper to sulfur ratio by mass is 1.00 g of S to 0.253 g of Cu. What are the copper to sulfur ratios in covellite and chalococite?

Would the answer be the following?

Covellite: Cu2S

Chalococite: Cu4S

Answer 1

Covellite is a soft, indigo-blue mineral in which the copper to sulfur ratio by mass is 1.00 g of S to 0.506 g of Cu.

0.506g Cu (1mol Cu/63.546g) = 7.962 x 10^-3 mol Cu

1.00g S (1mol S/32.065g) = 0.0311 mol S

mol Cu/mol S = 7.962 x 10^-3/0.0311 = 0.256/1

The ratio of Cu to S is about 0.256/1 or 1/1 .i.e. CuS

Chalococite is a soft, black mineral in which the copper to sulfur ratio by mass is 1.00 g of S to 0.253 g of Cu

0.253g Cu (1mol Cu/63.546g) = 3.981 x 10^-3 mol Cu

1.00g S (1mol S/32.065g) = 0.0311 x10^-2 mol S

mol Cu/mol S = 7.962 x 10^-3/3.118 x 10^-2 = 0.128/1

The ratio of Cu to S is about 0.128/1 or 1/1 .i.e. CuS