CHE 105/110 Introduction to Chemistry - Exercises and Answers

1.

What are the three colligative properties that involve phase changes?

1.

boiling point elevation, freezing point depression, vapor pressure depression

3.

If 45.0 g of C₆H₆ and 60.0 g of C₆H₅CH₃ are mixed together, what is the mole fraction of each component?

3.

mole fraction C₆H₆: 0.469; mole fraction C₆H₅CH₃: 0.531

5.

If 36.5 g of NaCl are mixed with 63.5 g of H₂O, what is the mole fraction of each component?

5.

mole fraction NaCl: 0.157; mole fraction H₂O: 0.843

7.

A solution is made by mixing 12.0 g of C₁₀H₈ in 45.0 g of C₆H₆. If the vapor pressure of pure C₆H₆ is 76.5 torr at a particular temperature, what is the vapor pressure of the solution at the same temperature?

7.

65.8 torr

9.

At 300°C, the vapor pressure of Hg is 32.97 torr. If 0.775 g of Au were dissolved into 3.77 g of Hg, what would be the vapor pressure of the solution?

9.

27.26 torr

11.

If 25.0 g of C₆H₁₂O₆ are dissolved in 100.0 g of H₂O, what is the boiling point of this solution?

11.

100.71°C

13.

If 1 mol of solid CBr₄ is mixed with 2 mol of CCl₄, what is the boiling point of this solution?

13.

92.9°C

15.

If 123 g of C₁₀H₁₆O are dissolved in 355 g of C₆H₆, what is the freezing point of this solution?

15.

−5.65°C

17.

C₈H₁₇OH is a nonvolatile solid that dissolves in C₆H₁₂. If 7.22 g of C₈H₁₇OH is dissolved in 45.3 g of C₆H₁₂, what is the freezing point of this solution?

17.

−18.3°C

19.

If 25.0 g of C₆H₁₂O₆ are dissolved in H₂O to make 0.100 L of solution, what is the osmotic pressure of this solution at 25°C?

19.

33.9 atm

21.

At 298 K, what concentration of solution is needed to have an osmotic pressure of 1.00 atm?

21.

0.0409 M