a) ms = 180g c = 20% ⇒ md = 36g NaOH mH2O = 144g
b) nNaOH = 36/40 = 0,9 moli nH2O = 144/18 = 8 moli
NaOH : H2O = 0,9/8 = 9/80 = 0 1125
c) n solutie = 0,9 + 8 = 8,9 moli %NaOH = 0,9·100/8,9 = 10,11%%
%H2O = 8·100/8,9 = 89,88%
d) X H2O = 8/8,9 = 0,8988
e) md = 36 + x c = 30% ms = 180+x
(36+x)·100/(180+x) = 30 360 + 10x = 540 + 3x x = 25,71 g
f) ms = 180 + y md = 36 g c = 15%
36·100/(180+y) = 15 180+y = 240 y = 60 g