Ch.17 - Applications of Aqueous Equilibria

Problem 1

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Chapter 17, Problem 1

Which of the following mixtures has the highest pH? (a) Equal volumes of 1.0 M HCl and 1.0 M NaOH (b) Equal volumes of 0.1 M HNO3 and 0.1 M KOH (c) Equal volumes of 0.1 M HCN and 0.1 M NaOH (d) Equal volumes of 0.1 M NaF and 0.1 M HCl

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Identify the nature of each component in the mixtures: strong acid, strong base, weak acid, or weak base.

For each mixture, determine the reaction that occurs when the acid and base are mixed, and identify the resulting solution's components.

Calculate the pH of the resulting solution for each mixture by considering the strength of the acids and bases involved.

Compare the pH values of the resulting solutions to determine which mixture has the highest pH.

Conclude which mixture has the highest pH based on the comparison of the calculated pH values.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Base Neutralization

Acid-base neutralization occurs when an acid reacts with a base to produce water and a salt. The pH of the resulting solution depends on the strength and concentration of the acid and base involved. Strong acids and bases, like HCl and NaOH, completely dissociate in solution, leading to a neutral pH of 7 when mixed in equal concentrations. However, weak acids and bases do not fully dissociate, affecting the final pH.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral. A lower pH indicates a higher concentration of hydrogen ions (H+), while a higher pH indicates a higher concentration of hydroxide ions (OH-). Understanding the pH scale is crucial for determining the outcome of acid-base reactions and predicting the pH of mixtures.

Buffer Solutions

Buffer solutions resist changes in pH when small amounts of acid or base are added. They typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid. In the context of the question, mixtures involving weak acids or bases, such as HCN or NaF, can create buffer-like behavior, influencing the final pH compared to strong acid-base combinations.

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Buffer Solutions

Related Practice

Consider the titration of 50.0 mL of 1.00 M H₃PO₄ with 1.00 M KOH. Calculate the pH after the addition of each of the following volumes of base. (b) 50.0 mL (d) 100.0 mL

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Textbook Question

Consider the titration of 50.0 mL of 1.00 M H₃PO₄ with 1.00 M KOH. Calculate the pH after the addition of each of the following volumes of base. (a) 25.0 mL (c) 75.0 mL

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Textbook Question

Consider the titration of 50.0 mL of a 0.100 M solution of the protonated form of the amino acid alanine (H₂A⁺: K_a1 = 4.6 × 10^–3, K_a2 = 2.0 × 10^–10) with 0.100 M NaOH. Calculate the pH after the addition of each of the following volumes of base. (b) 25.0 mL (c) 50.0 mL

Open Question

What is the percent dissociation in a solution that is 0.50 M in acetic acid (CH3CO2H) and 0.10 M in sodium acetate (NaCH3CO2)? (Ka = 1.8 x 10^-5) (a) 0.018% (b) 0.090% (c) 7.2 x 10^-3% (d) 2.3%

Textbook Question

A 1.00 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 M HCl. (Ka = 3.5 x 10^-4) (a) 4.11 (b) 3.82 (c) 3.46 (d) 3.09

What is the pH of a buffer solution prepared by dissolving 0.250 mol of NaH2PO4 and 0.075 mol of NaOH in enough water to make 1.00 L of solution? (Ka (H2PO4-) = 6.2 X 10^-8) (a) 6.32 (b) 6.83 (c) 7.21 (d) 7.71

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