Cm= md/MxVs ; M.NaOH = 23+16+1 = 40 g/mol
=> Cm = 0,4/40x0,1 = 0,1 mol/L = 10la-1 mol/L
NaOH = baza tare care va ioniza complet in solutie apoasa
=> [HO-] = Cm = 10la-pOH
=> 10la-1 = 10la-pOH => pOH = 1
stim ca pH + pOH = 14 => pH = 14-1 = 13
b.
turnesol = albastru
fenolftaleina = rosu-carmin