General Chemistry Review Chapters 16-20

Questions and Answers

Which of the following statements is true about a solution prepared with equal amounts of HNO2 and NaNO2?

This solution will resist changes in pH.

This solution contains a weak acid and its conjugate base.

If a small amount of strong acid is added to the solution, NaNO2 will neutralize it.

If a small amount of strong base is added to the solution, HNO2 will neutralize it.

All of the above. (correct)

Which of the following would produce a buffer?

HNO3 / NaNO3

HF / KF (correct)

HC2H3O2 / NH3

HClO4 / NaOH

NH3 / NaCl

What is the pH of a 1.0 L buffer solution containing 0.500 M HF and 0.300 M NaF?

3.46

1.88

3.24 (correct)

2.00

0.30

Determine the pH of a 1.0 L buffer prepared by adding 0.100 moles of NaOH to 0.250 moles of HF.

3.28 Signup and view all the answers

What mass of NaC2H3O2 (molar mass = 82.03 g/mol) would need to be added to 0.450 moles of HC2H3O2 to prepare a 1.0 L buffer with a pH = 4.95?

59.9 g Signup and view all the answers

What is the pH after the addition of 2.5 g of KOH to 1.0 L of a buffer that is 0.400 M in HF and 0.250 M in LiF?

3.37 Signup and view all the answers

The addition of which of the following would destroy a 1.0 L buffer that is 0.50 M HC2H3O2 and 0.40 M NaC2H3O2?

15.0 g HCl Signup and view all the answers

For a titration of a weak acid with a strong base, the pH at the equivalence point ________.

Is greater than 7 Signup and view all the answers

Calculate the volume (mL) of 0.500 M NaOH required to reach the equivalence point in the titration of 25.0 mL of 0.650 M HF.

32.5 Signup and view all the answers

What is the initial pH for the titration of 30.0 mL of 0.850 M NH3 with 0.100 M HCl?

11.60 Signup and view all the answers

20.0 mL of 0.500 M HC2H3O2 is titrated with 0.350 M KOH. Determine the pH after 15.0 mL of the base has been added.

4.79 Signup and view all the answers

Calculate the pH at the equivalence point for the titration of 20.0 mL of 0.500 M HC2H3O2 with 0.350 M KOH.

9.01 Signup and view all the answers

Determine the pH when 5.00 mL of excess KOH (beyond the equivalence point) has been added to the titration of 20.0 mL of 0.500 M HC2H3O2 with 0.350 M KOH.

12.51 Signup and view all the answers

What is the molar solubility of PbBr2 in pure water?

1.05 × 10−2 Signup and view all the answers

Determine the molar solubility of CaCO3 in a solution of 0.500 M Na2CO3.

9.92 × 10−9 Signup and view all the answers

Which of the following is (are) spontaneous processes?

(i) and (ii) only Signup and view all the answers

Calculate the entropy of a system that has 2.50 × 10^8 possible arrangements.

2.67 × 10^-22 J/K Signup and view all the answers

A positive ΔSsystem indicates what about the overall spontaneity of a process?

Nothing; only ΔSuniverse can tell about the overall spontaneity of a process. Signup and view all the answers

Study Notes

Buffer Solutions

A solution comprising equal amounts of HNO2 (weak acid) and NaNO2 (conjugate base) will resist pH changes, showcasing its buffering capacity.
The combination of HF (weak acid) and KF (its salt) generates a buffer system.

pH Calculations

A buffer solution of 0.500 M HF and 0.300 M NaF produces a pH of 3.24.
Adding 0.100 moles of NaOH to 0.250 moles of HF results in a pH of 3.28.
To achieve a pH of 4.95 with 0.450 moles of HC2H3O2, 59.9 g of NaC2H3O2 is required.
After adding 2.5 g of KOH to a buffer of 0.400 M HF and 0.250 M LiF, the pH rises to 3.37.

Titration Insights

The addition of 15.0 g of HCl can neutralize a buffer solution of 0.50 M HC2H3O2 and 0.40 M NaC2H3O2, effectively destroying its buffering ability.
In titrations involving weak acids and strong bases, the pH at the equivalence point is always greater than 7, indicating a basic environment.
Calculating the titration of 25.0 mL of 0.650 M HF with 0.500 M NaOH requires 32.5 mL of NaOH to reach the equivalence point.
For the titration of 30.0 mL of 0.850 M NH3 with 0.100 M HCl, the initial pH is notably basic at 11.60.

pH During Titration

The pH after 15.0 mL of 0.350 M KOH is added to 20.0 mL of 0.500 M HC2H3O2 is measured at 4.79.
At the equivalence point for the same titration, the pH is recorded at 9.01.
Adding 5.00 mL of excess KOH post-equivalence in the same titration raises the pH to 12.51.

Solubility Products

The molar solubility of PbBr2 in pure water is derived from its Ksp of 4.67 × 10−6, yielding a solubility of 1.05 × 10−2 M.
CaCO3 displayed a molar solubility of 9.92 × 10−9 M when in a solution with 0.500 M Na2CO3.

Spontaneous Processes and Entropy

Processes considered spontaneous include a ball rolling down a hill and the rusting of a car.
An entropy calculation shows that a system with 2.50 × 10^8 arrangements has an entropy of 2.67 × 10^-22 J/K.
A positive ΔSsystem alone cannot determine overall process spontaneity; ΔSuniverse must be analyzed.

Changes in Entropy

The formation of ice from water at −25 °C would have a negative ΔS, indicating reduced disorder compared to the liquid state.

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This quiz focuses on fundamental concepts from General Chemistry, specifically covering chapters 16 to 20. You will explore various chemical principles, including properties of solutions and acid-base reactions. Test your knowledge with these flashcards designed for review and consolidation of key ideas.