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Ch.16 - Acid-Base Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.16 - Acid-Base EquilibriaProblem 97
Chapter 16, Problem 97

Predict which member of each pair produces the more acidic aqueous solution: (a) K+ or Cu2+ (b) Fe2+ or Fe3+ (c) Al3+ or Ga3+.

Verified step by step guidance
1
Step 1: Understand the concept of acidity in aqueous solutions. Acidity in aqueous solutions is often related to the ability of a cation to polarize water molecules, leading to the release of protons (H+). This is influenced by the charge density of the cation.
Step 2: Analyze the charge and size of the cations. Higher charge and smaller ionic radius generally increase the charge density, making the cation more effective at polarizing water molecules and thus more acidic.
Step 3: Compare the cations in each pair based on their charge and size. For example, between K+ and Cu2+, Cu2+ has a higher charge and likely a smaller radius, making it more acidic.
Step 4: Apply the same analysis to the other pairs. For Fe2+ vs. Fe3+, Fe3+ has a higher charge, and for Al3+ vs. Ga3+, consider the periodic trends and charge density.
Step 5: Conclude which cation in each pair is more acidic based on the analysis of charge density and polarization ability.

Key Concepts

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

Acidity and pH

Acidity refers to the concentration of hydrogen ions (H+) in a solution, which determines its pH level. A lower pH indicates a more acidic solution. Understanding how different ions affect the concentration of H+ is crucial for predicting the acidity of solutions.

Cation Charge and Hydrolysis

Cations can influence the acidity of a solution through hydrolysis, where they react with water to produce H+ ions. Generally, cations with higher positive charges, such as Cu2+ and Fe3+, tend to hydrolyze more significantly than those with lower charges, leading to increased acidity.
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Comparative Analysis of Metal Ions

When comparing metal ions, factors such as charge density and the ability to stabilize the resulting hydroxide ions play a role in acidity. For instance, smaller, highly charged ions like Al3+ are more acidic than larger, less charged ions like Ga3+, due to their stronger attraction to water molecules and greater tendency to release H+.
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Related Practice
Textbook Question

Which, if any, of the following statements are true? (a) The stronger the base, the smaller the pKb. (b) The stronger the base, the larger the pKb. (c) The stronger the base, the smaller the Kb. (d) The stronger the base, the larger the Kb. (e) The stronger the base, the smaller the pKa of its conjugate acid. (f) The stronger the base, the larger the pKa of its conjugate acid.

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Textbook Question
The fluoride ion reacts with water to produce HF. (c) Is fluoride acting as a Lewis acid or as a Lewis base when reacting with water?
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Textbook Question

Indicate whether each of the following statements is correct or incorrect. (c) Conjugate acids of weak bases produce more acidic solutions than conjugate acids of strong bases.

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Textbook Question

Identify the Lewis acid and Lewis base among the reactants in each of the following reactions:

(a) Fe(ClO4)3(s) + 6 H2O(l) ⇌ [Fe(H2O)6]3+(aq) + 3 ClO4-(aq)

(b) CN-(aq) + H2O(l) ⇌ HCN(aq) + OH-(aq)

(c) (CH3)3N(g) + BF3(g) ⇌ (CH3)NBF3(s)

(d) HIO(lq) + NH2-(lq) ⇌ NH3(lq) + IO-(lq) (lq denotes liquid ammonia as solvent)

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Textbook Question

Identify the Lewis acid and Lewis base in each of the following reactions:

(a) HNO2(aq) + OH-(aq) ⇌ NO2-(aq) + H2O(l)

(b) FeBr3(s) + Br-(aq) ⇌ FeBr4-(aq)

(c) Zn2+(aq) + 4 NH3(aq) ⇌ Zn(NH3)42+(aq)

(d) SO2(g) + H2O(l) ⇌ H2SO3(aq)

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Textbook Question

A solution is made by adding 0.300 g Ca1OH221s2, 50.0 mL of 1.40 M HNO3, and enough water to make a final volume of 75.0 mL. Assuming that all of the solid dissolves, what is the pH of the final solution?

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