A solution contains 40.0 g of sodium chloride and 200.0 g of water. Calculate the NaCl

Question

concentration as a a) mass percentage, b) molality, c) mole fraction.

I have trouble finding mole fraction. I believe I've got the other two, but I'm not 100% sure.

Answer 1

% w/w = 16.7
m = 3.42
If you didn't get these show your work and I'll find the error.

mols NaCl = grams/molar mass
mols H2O = grams/molar mass
XNaCl = mols NaCl/total mols.
I worked it quickly and obtained 0.381 but you should confirm that.
As a check run XH2O and see if you get 1-0.381 because XNaCl + XH2O must = 1.00(within rounding error).

Answer 2

Dr.Bob, Could you please show the work for w/w and mol frac. I continue to get a completely bizarre number. The only one that I am getting correct is the molal part.

Answer 3

I was able to find both the Mol Frac and m now. The only problem is w/w.

m) (40.0gNaCl)*(1molNaCl/58.33gNaCl)=.684mol Nacl
-200.0gH20*(1molH20/18.02gH20)=11.mol H20
-200g= .2L
** .684mol NaCl/.2LH20= m=3.42

Mol Frac) .864molNaCl/(.864molNaCl+11.02)= .580

w/w .684/11.02= 3.63