Question

Ma puteti ajuta cu problema 5.3 din imagine?

Answer 1

a)  ms = 180g    c = 20%   q= 1,22g/cm³
md = c·ms/100 = 36g NaOH    n = 36/40 = 0,9 moli
b)  m H2O + 180 - 36 = 144g  n = 144/18 = 8moli
nNaOH / nH2O = 0,9/8
c)  solutia contine 0,9moli NaOH + 8moli H2O  = 8,9 moli
cNaOH = 0,9·100/8,9 = 10,11%
d)  X H2O = 8/8,9 = 0,898
e)  Vs = ms/q = 180/1,22 = 147,54cm³ = 0,14754 l
cM = nNaOH/Vs = 0,9/0,14754 = 6,1 mol/ l
f)  c1 = 1,5·20 = 30%    ms = 180 + x    md = 36 + x
(36 + x)·100/(180+x) = 30
360 + 10x = 540+3x    7x = 180  x = 25,7gNaOH
g)  c = 15%  md = 36g    ms = 180+x
36·100/(180+x) = 15      240 = 180+ x    x = 60gH2O