CuSO4+2NaOH=Cu(OH)2+Na2SO4
1) n(CuSO4)=m(CuSO4)/M(CuSO4)=4/160=0.025
2) n(CuSO4)*2=n(NaOH)=0.025*2=0.05
3) m(NaOH)=M(NaOH)*n(NaOH)=40*0.05=2
4) m(раствора гидроксида натрия )=m(NaOH)/w(NaOH)=2/0.08=25 г