Question

7. What is the mole fraction of urea, CH4N2O, in an aqueous solution that is 46% urea by mass? 8. What volume of a 0.850 M solution of CaCl2 contains 1.28 g of solute? 9. The volume of a 27.0% (by mass) solution is 162.9 mL. The density of the solution is 1.128 g/mL. What is the mass of solute in this solution? 10. Concentrated sodium hydroxide is 19.4 M and has a density of 1.54 g/mL. What is the molality of concentrated NaOH? 11. What is the freezing point of an aqueous 2.08 m NaCl solution? (Kp for water is 1.858°C/m.) 12. What is the freezing point of a 0.27 m solution of glucose, CaH12Oe, in water? (Kp for water is 1.858°C/m.)

Answer 1

Here you go:

7) We have urea as 46% by mass. So if we have a 100 gm solution of urea then we have 46 gm urea and 54 gm water.

So the number of moles of urea, n1 = 46/60.06 moles = 0.766 moles.

And no of moles of water present, N2 = 54/18 moles = 3 moles.

Thus mole fraction of urea, x1 = n1/(n1+n2) = 0.766/3.766 = 0.203

According to HOMEWORKLIB RULES I can't answer the rest of the questions and please post it separately!!