Questions and Answers
Which of the following statements is true about a solution prepared with equal amounts of HNO2 and NaNO2?
Which of the following would produce a buffer?
What is the pH of a 1.0 L buffer solution containing 0.500 M HF and 0.300 M NaF?
Determine the pH of a 1.0 L buffer prepared by adding 0.100 moles of NaOH to 0.250 moles of HF.
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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?
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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?
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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?
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For a titration of a weak acid with a strong base, the pH at the equivalence point ________.
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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.
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What is the initial pH for the titration of 30.0 mL of 0.850 M NH3 with 0.100 M HCl?
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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.
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Calculate the pH at the equivalence point for the titration of 20.0 mL of 0.500 M HC2H3O2 with 0.350 M KOH.
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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.
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What is the molar solubility of PbBr2 in pure water?
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Determine the molar solubility of CaCO3 in a solution of 0.500 M Na2CO3.
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Which of the following is (are) spontaneous processes?
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Calculate the entropy of a system that has 2.50 × 10^8 possible arrangements.
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A positive ΔSsystem indicates what about the overall spontaneity of a process?
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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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Description
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.