CHM12 - Long Quiz 5 - 4th Term - 20092010

GENERAL CHEMISTRY                                                                             EXAM NO.5

TOPICS: Aqueous Solutions and Colligative Properties                

*Write your answers in yellow booklet.

*Submit the Take Home Exam on June 26, 2010, Saturday at 9 AM at N404.

*Bring the Course Syllabus of CHM12 for Course Syllabus.

I. TRUE or FALSE. Right minus wrong. Write T if the statement is TRUE and F if the statement is FALSE. (20 pts)

1. Water is considered as a universal solvent.

2.  Strong electrolytes dissociate in water completely.

3. If a solute is nonvolatile the vapor pressure of its solution is always less than that of the pure solvent.

4.  A solution is less disordered than that of a pure solvent.

5. The solute must be nonvolatile for the boiling-point elevation and vapor pressure lowering.

6.  Osmotic pressure is directly to the concentration the solution.

7. The movement of solvent molecules in osmosis is from higher concentration to a lower concentration.

8.  With respect to the solubility of gas in liquid, solubility is directly proportional to the temperature.

9. All colligative properties are affected by the presence of an electrolyte:

10. Commonly, weak acids are 5% ionized or less.

II. Identification. Write the answer (must be properly spelled and no acronyms) described in each item below. (20 pts)

1. It allows the passage of the solvent molecules but blocks the passage of solute molecules.

2. It is the ratio of the actual number of particles in solution after dissociation and the number of formula units initially dissolved in the solution.

3. These properties depend on the concentration of dissolved particles and not on their nature

4. It is the states that the partial pressure of the solvent over a solution is given by the product of the vapor pressure of the pure solvent and the mole fraction of the solvent in the solution.

5. It is the pressure required to prevent osmosis from occurring.

6. Ions that are not involved in the overall reaction.

7. It is the process of measuring the volume of a standard solution (known concentration) needed to react with a measured quantity of a sample.

8. It is the oxidation number of an element in an elementary substance.

For Nos. 9 and 10, consider the reaction:

Zn (s) + 2 H+ (aq) → Zn2+ (aq) + H2 (g)

9. It is the substance that is reduced.

10. It is the reducing agent.

III. Answer the following questions. Show the equations and/or computations necessary to support your answers. (125 ts)

1.      Predict the precipitate produced by the following reaction and write a net ionic equation for the reaction between Al(NO₃)_3(aq) and NaOH. (5 pts)

2.      Write the ionic and net ionic equations for the following reactions: (5 pts each)

1. BaCl_{2 (aq)} + ZnSO_{4 (aq)}
2. (NH₄)₂CO_3(aq) + CaCl_2(aq)
3. K₃PO_4(aq) + Sr(NO₃)_2(aq)
4. CH₃COOH_(aq) + KOH_(aq)
5. Ba(OH)_2(aq) + H₃PO_4(aq)\
6. HBr_(aq) + NH_3(aq)

3.      Balance the following redox equation by the ion-electron method. (10 pts each)

a.      MnO₄^- + SO₂ à Mn²⁺ + HSO₄^-

The reaction occurs in acidic solution.

b.     Cu + HNO₃ à Cu²⁺ + NO + H₂O

The reaction occurs in acidic solution.

c.      Bi(OH)₃ + SnO₂^2- à SnO₃

The reaction occurs in basic solution.

d. Br₂ à BrO₃^- + Br^-

The reaction occurs in basic solution.

4.      How many grams of sucrose (C₁₂H₂₂O₁₁) must be added to 552 g of water to give a solution with a vapor pressure 2.0 mmHg less than that of pure water at 20^oC? (The vapor pressure of water at 20^oC is 17.5 mmHg). (10 pts)

5.      An aqueous solution contains the amino acid glycine (NH₂CH₂COOH). Assuming no ionization of the acid, calculate the molality of the solution if it freezes at -1.1^oC. (10 pts)

6.      A solution containing 0.8330 g of a protein of unknown structure in 170.0 ml of aqueous solution was found to have an osmotic pressure of 5.20 mmHg at 25^OC. Determine the molar mass of the protein. (10 pts)

7.      Lysozome is an enzyme that cleaves bacterial cell walls. A sample of lysozome extracted from chicken egg white has a molar mass of 13, 930 g. A quantity of 0.100 g of this enzyme is dissolved in 150 g of water at 25^oC. Calculate the elevation in boiling point. (10 pts)

8.      What minimum pressure must be applied to seawater at 25^oC in order to carry out the reverse osmosis process? Treat seawater as a 0.70M NaCl solution. (10 pts)

ADNieva                                                                                                                                                           4Q 2009-2010