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CHEMISTRY: CHAPTER 4

SOLUTIONS



1. What is the final concentration of Cl- ion when 250 mL of 0.20 M CaCl2 solution is mixed with 250 mL of 0.40 M KCl solution? (Assume additive volumes.)
(A) 0.10 M
(B) 0.20 M
(C) 0.30 M
(D) 0.40 M
(E) 0.60 M


2. What volume of water should be added to 0.40 L of 6.0 M H2SO4 solution to produce a solution that is 2.0 M H2SO4?
(A) 0.40 L
(B) 0.80 L
(C) 1.2 L
(D) 1.6 L
(E) 2.4 L


3. Which of the following 0.20 M water solutions has the highest freezing point? (Assume ideal behavior.)
(A) urea, (NH2)2CO
(B) nitrogen pentoxide, N2O5
(C) ammonium chloride, NH4Cl
(D) ammonium phosphate, (NH4)3PO4
(E) ammonium hydrogen sulfate, NH4HSO4


4. A water solution of sucrose (C12H22O11, molar mass = 342) is known to be 6.0 molal. What one additional characteristic of the solution could be used to determine its density?
(A) mass
(B) molarity
(C) boiling point
(D) freezing point
(E) percent by mass


Solutions



5. Which expression gives the mole fraction of H2SO4 in a water solution that contains 3.0 moles of H2SO4 in 90. grams of water?


6. Which change is most likely to increase the solubility of an ionic solid in water?
(A) increasing the surface area of the solid in the system
(B) increasing the volume of water available in the system
(C) increasing the temperature of the system
(D) increasing the external pressure on the system
(E) increasing the mass of ionic solid available in the system


7. What piece of laboratory apparatus is least likely to be used to prepare a quantity of standard 1.00 M BaCl2 using solid BaCl2.2H2O and distilled water?
(A) funnel
(B) crucible
(C) thermometer
(D) volumetric flask
(E) laboratory balance


8. What is the percent methanol by mass in a solution that contains 20 grams of methanol,
CH3OH, in 30 grams of water?
(A) 20%
(B) 33%
(C) 40%
(D) 60%
(E) 67%


Solutions


9. A standard solution of sodium hydroxide can be used in a titration experiment to determine the formula mass of a solid acid. A common mistake in such a titration experiment is the failure to rinse the buret with the standard solution after the final water rinse but before measurements of the volume of the standard solution are taken. This mistake accounts for which of the following results?
I.
The volume of the standard solution used in the titration reaction is reported too small.
II. The volume of the solute used to dissolve the unknown acid is reported too small.
III. The number of moles of unknown acid used in the titration reaction is reported too large.
(A) I only
(B) II and III only
(C) III only
(D) I and III only
(E) I, II, and III


10. Which substance is most likely to be found in an aqueous solution that is both saturated and dilute at room temperature?
(A) sucrose
(B) silver acetate
(C) sodium chloride
(D) ammonium carbonate
(E) potassium hydroxide


11. Which substance is least likely to be found in an aqueous solution that is concentrated?
(A) sodium phosphate
(B) hydrogen bromide
(C) magnesium hydroxide
(D) aluminum chloride
(E) ammonium nitrate


12. The level of arsenic permitted in drinking water is 0.050 ppm (parts per million). Which of the following is another way to express that same concentration?
(A) 0.050 mg As/milliliter H2O
(B) 0.050 mg As/liter H2O
(C) 0.050 g As/million liters H2O
(D) 0.050 mg As/million liters H2O
(E) 0.050 mg As/million grams H2O


Solutions


Questions 13-14 refer to the solubility curve for KCl in water as shown below.

13. What is the molality of a saturated solution of KCl (molar mass 74.6) at 35C?
(A) 0.37
(B) 0.50
(C) 2.0
(D) 3.7
(E) 5.0


14. A saturated solution of KCl at 75C contains 100 g water. Which value is closest to the percent by mass of KCl in the solution?
(A) 33
(B) 50
(C) 60
(D) 67
(E) 75

Questions 15 and 16 refer to the solubility curve for KCl in water shown above. A mixture containing 100 g H2O and 40. g KCl is warmed to 60C and thoroughly stirred until no further changes occur.


15. The resulting system is best desribed as
(A) a colloid
(B) a suspension
(C) a saturated solution
(D) an unsaturated solution
(E) an isotonic solution


16. When the system is cooled from 60C to 30C, a white crystalline solid forms. Which is the best description of the liquid phase of the system?
(A) 50 g solution including 20 g solute
(B) 60 g solution including 40 g solute
(C) 100 g solution including 35 g solute
(D) 120 g solution including 20 g solute
(E) 135 g solution including 35 g solute


Solutions


Questions 17 and 18 refer to the table of information below. The molar masses and vapor pressures of benzene and toluene at 20C are given in this table.


17. Consider a solution whose mole fraction is 0.40 toluene Xtoluene = 0.40. Which location on this scale is the best estimate of the vapor pressure of the solution?

(A) A
(B) B
(C) C
(D) D
(E) E


18. For the solution described in question 17, which gives the best comparison between the ratio of the number of molecules of each substance in the liquid phase and the ratio of the number of molecules of each substance in the vapor phase over the liquid at 20C?


Solutions


19. Which accounts for the Tyndall effect in colloids?
(A) scattering of light by particles of matter
(B) absorption of light by particles of matter
(C) absorption of light of specific wavelength in the visible range
(D) absorption of light of specific wavelength in the ultraviolet range
(E) alternating patterns of refraction and reflection of light by lattice particles


20. A hydrophobic colloid is most likely to be stabilized in water by the presence of
(A) sodium ions
(B) stearate ions
(C) hydrogen ions
(D) sucrose molecules
(E) benzene molecules


21. Which applies to a 1.0 molar solution of potassium nitrate in water?
I.
Adding water raises the freezing point.
II. Adding water increases the vapor pressure of the solution.
III. Adding water decreases the density of the solution.
(A) I only
(B) II and III only
(C) I and III only
(D) II and III only
(E) I, II, and III


22. Compared to water, a 0.20 M solution of NaCl will have all of the following properties EXCEPT:
(A) greater density
(B) lower vapor pressure
(C) lower boiling point
(D) lower freezing point
(E) greater osmotic pressure


Solutions


23. In a spontaneous, exothermic dissolving process, which of these values has a negative sign?
I.
Gsoln
II. Hsoln
III. T
(A) I only
(B) III only
(C) I and II only
(D) II and III only
(E) I, II, and III


24. A saturated solution of KNO3 in equilibrium with excess solute is prepared at 20C. Which of the following describe the solution after the temperature of the system is increased to 40C while still in contact with excess solute?
I.
The molality of the solution increases.
II. The solution remains saturated.
III. The density of the solution increases.
(A) II only
(B) III only
(C) I and III only
(D) II and III only
(E) I, II, and III


25. A dilute solution of NaCl is prepared at 20C. Which of the following describes the solution after the temperature of the solution is increased 40C?
I.
The vapor pressure of the solution increases.
II. The number of ion pairs in solution increases.
III. The difference between the freezing point and the boiling point increases.
(A) I only
(B) III only
(C) I and II only
(D) I and III only
(E) I, II, and III


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Answer Key]