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chem

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an aq. solution(NaCl) made by using 133g diluted to a total solution volume of 1 L.Calculate the molarity, molality & mass % of the solution(density of solution = 1.08g/mL)
[ans: M=1.92M, m=2.0m, 10.4 %]
i need the calculation work bcus my ans is contradict from the real ans.

~for M i got 2.28M
my calculation: M=2.28/1
but the ans is 1.92M.
~for m i got same with the ans.
~for the mass% i got 12.31%
my calculation: mass%=133/1080x100%
but the ans is 10.4%

  • chem -

    Unless I have missed something in reading the problem, I agree with your answer of 2.28M as well as with 12.31% although I might round that to 12.3%. I don't agree with the 2.0m
    (Note: 1.92M comes out VERY close to 2.0 m--actually about 1.98 and using 2.0m gives 10.4% so if the 1.92 is off and the answer book used that as a guide for the others then all will be off).
    For m, I get something close to 2.40m.
    2.28 x 58.44 = 133 g
    Soln has mass of 1080 and that -133 g leaves 967 g solvent (or 0.967 kg). Then 2.28/0.967 = 2.40m and that could be changed by 0.01 or so due to rounding. You may want to do that more accurately than I.

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