a)md=4g ms=4+46=50g c=md.100/ms=2%
b)NaOH+HCl=NaCl+H2O
40g.....36,5....58,5g
4g...........x.........y
x=3,65g HCl consumat in reactie
y=5,85g NaCl rezultată din reactie
md1=c1.ms1/100=36,5.50/100=18,25g acid clorhidric in solutie
mHCl exces=18,25-3,65=14,6g