msf2=1790g
mCac2=800g
p=80%
MCaC2=64g/mol
MH2O=18g/mol
0.8*800=640g CaC2 pur
0.2*800=160g CaC2 impur
CaC2 + 2H2O --> C2H2 + Ca(OH)2
64g CaC2.........36g 2H2O
640g.......x=360g
ms1=md+mH2O=640+360=1000g
64g CaC2..........36g 2H2O
160g...................x=90g
ms2=md+mH2O=160+90=250g
msf1=ms1+ms2=1000+250=1250g
msi=msf2-msf1=1790-1250=540g