a) c% = mdx100/ms
b) ms = md+m.apa = 80+320 = 400 g sol. NaOH
=> c% = 80x100/400 = 20%
c) notam cu a = masa de apa evaporata
ms2 = ms-a = 400-a
c2 = 2c1 = 40%
=> 40 = 80x100/(400-a)
=> a = 200 g apa evaporata
d) M.NaOH = 23+16+1 = 40 g/mol
40g NaOH ......................... 16g O
100% ...................................... a% = 40%
e) NaOH + HCl --> NaCl + H2O