CHEM 1215 Unit 5 Practice Problems

 

 

1.      Predict whether DS will be positive, negative, or nearly zero for each of the following:

a.      shredding a piece of paper

b.   Ag+ (aq) +  Cl- (aq) à AgCl (s)

c.   melting a piece of ice

 

2.      Calculate the values for DH and DS for the following reaction and then use the definition to calculate the DG at 25oC:

a.  P4O10 (s) + 6 H2O (l) à 4 H3PO4 (aq)

 

3.      Calculate the value of DGo for the following reaction using the standard free energies of formation.

a.  SO2(g) + 2 H2 (g) à S (s) + 2 H2O (g)

 

4.      For the reaction in question 3, calculate the value of the equilibrium constant at 298K.

 

 

5.      Use the information from questions 3 and 4.  If the equilibrium concentrations of SO2 and H2 are 0.0050 M and 0.010 M, respectively, what is the concentration of water vapor at equilibrium?

 

6.      Calculate the maximum work that can be obtained from the combustion of 25.0 g of HC2H3O2 if the products are cooled to 25oC.

 

 

7.      At equilibrium, a saturated solution of cobalt (II) hydroxide contains 6.88 x 10-6 M Co2+ and 1.38 x 10-5 M OH-.  What is the value of DGo for the dissolution of cobalt (II) hydroxide?

 

8.      At the boiling point of a substance, the liquid and gas phases are in equilibrium.  Use the enthalpy and entropy data found in your text, calculate the boiling point of benzene, C6H6.

 

9.      Consider the following hypothetical reaction:  2 A (g) + B (l) à  3 C (g).  If this reaction is endothermic, under what conditions will the reaction be spontaneous?

 

10.  Determine the oxidation number for each element in the following compounds:

 

KMnO4                  K _______       Mn  ______     O  ______

H2                          H ______

Sn(CO3)2              Sn  _____        C  _____         O  _____

 

 

11.  Balance the following reactions using the half reaction method:

 

MnO4- (aq)  +  Cl- (aq) à Mn2+ (aq)  +  Cl2 (g)        (acidic solution)

 

 

MnO4- (aq)  +  I- (aq)  à  MnO2 (s)  +  I2 (aq)         (basic solution)

 

12.  Given the following reduction half-reactions, write the balanced equation for the spontaneous reaction that would occur in a galvanic cell.  Calculate the standard cell potential for the galvanic cell.  Write the equation for the reaction that actually occurs at the anode.

 

                        Al3+ (aq) + 3 e- à Al (s)                      Eored = -1.66 V

                        I2 (s) + 2 e-   à 2 I- (aq)                       Eored = 0.54 V

 

 

13.  Given that Eored (cathode) = 0.60V and Eored (anode) = -1.77 V, calculate the equilibrium constant for the reaction: 

 

S2O62- (aq) + N2 (g) + H2O (l) + 2 H+ (aq) à 2 H2SO3 (aq) + N2O (aq)

 

 

14.  Calculate the emf of the redox reaction shown in question 13 at 298K when the following concentrations are used:  [S2O62-] = 0.500 M, [N2] = 1.00 M, [H+] = 2.00 M, [H2SO3] = 1.50 M and [N2O] = 2.00 M.

 

 

15.  Identify the oxidant and reductant in the reaction shown in question 13.

 

 

16.  What will happen to the value of E for the reaction shown in question 13 if the following changes are made:

 

Sodium hydroxide is added?

The partial pressure of nitrogen increases?

 

17.  Which of the following is the stronger oxidizing agent:  Cr2O72-  or  BrO3- ?

 

 

18.  What volume of 0.125 M HCl is needed to neutralize 1.55 g of Mg(OH)2?

 

 

19.  What volume of 1.25 M NaOH is needed to neutralize 25.0 mL of 3.00 M H2SO4?

 

 

20.  What is the molarity of a solution prepared by dissolving 10.0 g of aluminum nitrate in enough water to prepare 250.0 mL of solution?

 

21.  What is the concentration of nitrate ions in 225 mL of a solution that contains 5.00 g of aluminum nitrate and 5.00 g of sodium nitrate.