M CuSO4= 64+32+4*16=160 g/mol
M H2O= 2*1+18= 18 g/mol
M CuSO4*5H2O= 160 + 5*18=250 g/mol
c%= md/ ms * 100
250 g CuSO4*5H2O..... 160 g CuSO4.....90 g apa
25 g CuSO4*5H2O..... x..........................y
x= 16 g CuSO4
y= 9 g H2O
in solutie avem CuSO4 si H2O
md= m CuSO4= 16 g
m apa= 9 + 175=184 g
m solutie= md + m apa= 16+184=200 g
c= 16/200*100=8%