A solution was prepared by dissolving 29.0 g of KCl in 225 g of water.
A)Calculate the mass percent of in the solution.
B) Calculate the mole fraction of in the solution.
C)Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL and what is teh molality of KCl
all these answers were great but the last part was for molality which required the mass of solvent on denominator.. thats all and i got the answer..thanks!!
3 Answers

b) 225 g water
mol = 225g / 18.016g/mol = 12.5 mol water
29.0 g KCl
mol = 29.0 / 74.55g/mol = 0.389 mol KCl
Therefore mole fraction KCl = 0.389 / (.389 + 12.5) = 0.030
c) from above, mol KCl is 0.389, vol = 0.239L
Molarity = 0.389mol / 0.239L = 1.63 mol/L

Mass percent and mole fraction work pretty much the same way – they are both percentages. Any percent is sample / total x 100.
A) is straight forward. B) Convert both to moles and the sample / total.
C) If the solvent is water, then molarity and molality are the same thing as the density of water 1g/ml – Liters = Kilograms.
Convert the KCl to mole and then divide by lters.

I can only answer A. Divide KCl with H20. So 29g/225g = 0.13 times 100. It’s about 13% mass in the solution.