Question

Determinati cati moli si cate molecule de piatra vanata trebuie adaugate peste 300 g solutie sulfat de cupru 25%, astfel incat sa se ajunga la concentratia de 40%?
multumesc

Answer 1

c=md/ms*100=>md=c*ms/100
md CuSO4=25*300/100=75g
Fie x-masa de piatra vanata adaugata [(cristalohidrat (ch)]
      n-nr. de moli de ch adaugat
      N-nr de molecule de ch adaugat
M CuSO4*5H2O=160+90=250g/mol
250g ch......160g CuSO4......90g H2O
xg ch...........a g CuSO4.........b g H2O
a=160x/250=0,64x g CuSO4
b=90x/250=0,36x g H2O
mdf=mCuSO4+md=(0,64x+75)g
msf=mch+ms=(x+300)g
cf=mdf/msf*100=>40=(0,64x+75)/(x+300)*100=>40/100=(0,64x+75)/(x+300)=>40(x+300)=100(0,64x+75)=>
=>40x+12000=64x+7500=>24x=4500=>x=4500/24=187,5g ch adaugat.
n=m/M=> n=187,5/250=0,75 moli de ch adaugat
n=N/NA=>N=n*NA=0,75*6,022*10^23=4,5165*10^23 molecule