MC=12g/mol
MCuO=ACu+AO=64+16=80g/mol
MCO2 = AC+2AO=12+2*16=44g/mol
MCu=64g/mol
a) C + 2CuO = CO2 + 2Cu
12g C...............2*80g CuO
1,2g C.................x=16g CuO (m pur)
puritatea = mpur/ mimpur*100 => mimpur=mpur*100/puritate = 16*100/80 = 20g CuO
b) 12g C......................44g CO2
1,2g C..........................4,4g CO2
c) 12g C......................2*64g Cu
1,2g C............................x=12,8g Cu