Question

How much Cu2S is needed to make 256.0 g Cu? How much SO2 is produced?

Answer 1

molar mass of Cu = 63.5 g/mol
number of mole of Cu = (given mass)/(molar mass)
= 256/63.5
= 4.03 mole
reaction taking place is
Cu2S + O2 --> 2Cu + SO2
according to reaction
2 mole of Cu is produced by 1 mole of Cu2S
1 mole of Cu is produced by 1/2 mole of Cu2S
4.03 mole of Cu is produced by (1/2)*4.03 mole of Cu2S
number of mole of Cu2S required = 2.02 mole

molar mass of Cu2S = 159 g/mol
mass of Cu2S required = (number of mole of Cu2S)*(molar mass of Cu2S)
= 2.02*159
= 321.2 g

again according to reaction
1 mole of Cu2S give 1 mole of SO2
2.02 mole of Cu2S give 2.02 mole of SO2
number of mole of SO2 produced = 2.02 mole

molar mass of SO2 = 64 g/mol
mass of SO2 produced = (number of mole of SO2)*(molar mass of SO2)
= 2.02*64
= 129.3 g