M,NaOH=40g/mol
M,NaCl= 58,5g/mol
c= mdx100/ms---->ms=md+m,apa= 4g+46g=50g
c= 4x100/50%=8%
md,acid= cxms/100= 36,5x50./100g=36,5/2gHCl
niuNaOH=m/M=4/40mol=0,1mol
niuHCl=36,5//2x36,5mol= 0,5mol
1mol.........1mol........1mol
HCl + NaOH---> NaCl +H2O
x..............0,1mol......y
y=0,1molNaCl----> m=niuxM=0,1X58,5g=.......................calculeaza
acidul este in exces, cu: 0,5mol-x=0,5-0,1=>0,4mol