Solubility Product Constant - General Chemistry - Quiz, Exercises of Chemistry

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1. 10 pts. Circle T or F to indicate if the statement is True or False:

T or F In order for an exothermic reaction to occur, the reactants must be less entropic than the products.

T or F A buffer solution can be made by combining a weak acid and its conjugate base in roughly equal proportions.

T or F When a solution containing a weak acid is titrated with a strong base, the pH at the equivalence point will be less than 7.

T or F In a constant-volume (bomb) calorimeter, the heat that is given off by the reaction is equal to the difference in energy between products and reactants.

T or F According to the second law of thermodynamics, the entropy of a chemical system can decrease only of the entropy in the surroundings increases by a greater amount.

2. 20 pts. Place your answers with units in the box to the left of each question. Use the correct number of significant figures. You will find scratch area and constants on the last page of this exam.

For a chemical process that gives off a gas, we observe that 35 kJ of heat is taken from the environment into the reaction vessel while 50 kJ of work is done by the expanding gas. What is the change in energy for the reaction (sign included)? What is the pH of a buffer solution that is 0.100 M weak acid and 0.120 M in its conjugate base? The Ka of the weak acid is 3.4 x 10-5.

In the following reaction, AgCl ( ) s Ag ( aq ) Cl ( aq )

• −

→ + , which is

more entropic, the reactants or the products? The solubility-product constant for PbSO 4 is 1.6x10-8. How many moles of lead (II) sulfate will dissolve in 1.0 L of solution?

Using the table provided with the exam, compute the free energy change (∆G) for the following reaction at a temperature of 298 K:

CCl 4 ( g ) + 2 H 2 ( g ) → CH 4 ( g ) + 2 Cl 2 ( g )

3. 5 pts. The heat capacity of a certain liquid is 0.317 J/g-K. If a 15.0 gram sample of this liquid at 25.0 °C is subjected to 1.50 kJ of heat, what will be the final temperature of the sample?
4. 5 pts. What is the pH of a solution prepared by mixing 65.0 mL of a 0.1920 M NaOH with 35.0 mL of a 0.4500 M acetic acid solution (HAc)?
5. 10 pts. A student uses a buret to transfer 20.00 mL of a 0.1000 M HCl solution to a 100.0 mL volumetric flask. Then she adds to this 20.00 mL of a 0.1000 M diethylamine solution. Finally she uses water to fill to the mark. What is the concentration of all ions in the resulting solution? What is the pH of the resulting solution? Be sure to answer both of these questions for full credit.

5. 10 pts. A student uses a buret to transfer 10.00 mL of a 0.1500 M NaOH solution into a flask already containing 20.00 mL of a 0.1500 M benzoic acid solution. What is the pH of the resulting solution?
6. 10 pts. When 135 grams of water at 25 °C are mixed with 55 grams of water at 75 °C, what is the final temperature of the mixture? Assume that there is no heat lost to the surroundings.
7. 10 pts. Using the thermodynamic parameters provided, calculate both the enthalpy change and the entropy change for the reaction:

2 SO 2 (g) + O 2 (g) → 2 SO 3 (g)

Is this process favorable from an enthalpic point of view? Explain.

Is this process favorable from an entropic point of view? Explain.

At what temperatures will this reaction be spontaneous?

8. 10 pts. Consider the following reaction:

2 NO(g) + O 2 (g) → N 2 O 4 (g)

a. Using the thermodynamic data table provided with the exam, calculate the molar Enthalpy change associated with this reaction.

b. Now suppose 13 atm of NO are reacted with 6 atm of diatomic oxygen gas. What would be the actual heat change in this case? Is the heat consumed or released? Assume conditions are 1.0 L and 300. K. The Ideal Gas constant is 0.0821 atm-L/mol-K.

9. 5 pts. Using only the following information,

O (g) NO(g) H 90.3 kJ/mol

2

1

N (g)

2

1

2 + 2 → ∆ =+

Cl (g) NOCl(g) H -38.6 kJ/mol

2

1

NO (g) + 2 → ∆ =

calculate the enthalpy change for this reaction:

2 NOCl(g) → O 2 (g) + N 2 (g)+Cl 2 (g) ∆H=?

10. 5 pts. Given the following information,

S (g) + O 2 (g) → SO 2 (g) ∆H=-580. kJ/mol

2 S(g) + 3 O 2 (g) → 2 SO 3 (g) ∆H=-1350. kJ/mol

calculate the enthalpy change for this reaction:

2 SO 2 (g) + O 2 (g) → 2 SO 3 (g) ∆H=?