Textbook Question
Which of the following compounds are more soluble in acidic solution than in pure water? Write a balanced net ionic equation for each dissolution reaction. (b) Fe(OH)3
Ch.17 - Applications of Aqueous Equilibria
Chapter 17, Problem 115
Consider saturated solutions of the slightly soluble salt AgBr. Is the solubility of AgBr increased, decreased, or unaffected by the addition of each of the following substances? (a) HBr, (b) HNO3, (c) AgNO3, (d) NH3.
Verified step by step guidance1
Step 1: Understand the concept of solubility equilibrium. AgBr is a slightly soluble salt, and its solubility can be represented by the equilibrium: AgBr(s) ⇌ Ag⁺(aq) + Br⁻(aq). The solubility product constant (Ksp) governs this equilibrium.
Step 2: Analyze the effect of adding HBr. HBr is a strong acid that dissociates completely in water to give H⁺ and Br⁻ ions. Adding HBr increases the concentration of Br⁻ ions, which shifts the equilibrium to the left according to Le Chatelier's principle, decreasing the solubility of AgBr.
Step 3: Consider the addition of HNO3. HNO3 is a strong acid that dissociates to give H⁺ and NO₃⁻ ions. Since neither of these ions directly affects the Ag⁺ or Br⁻ ions in the solubility equilibrium, the solubility of AgBr is unaffected by HNO3.
Step 4: Evaluate the effect of adding AgNO3. AgNO3 dissociates to give Ag⁺ and NO₃⁻ ions. The increase in Ag⁺ ion concentration shifts the equilibrium to the left, decreasing the solubility of AgBr due to the common ion effect.
Step 5: Assess the impact of adding NH3. NH3 can react with Ag⁺ ions to form a complex ion, [Ag(NH3)2]⁺, which reduces the concentration of free Ag⁺ ions. This shifts the equilibrium to the right, increasing the solubility of AgBr.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Solubility Product Constant (Ksp)
The solubility product constant (Ksp) is an equilibrium constant that applies to the solubility of sparingly soluble ionic compounds. It is defined as the product of the molar concentrations of the ions, each raised to the power of their coefficients in the balanced equation. For AgBr, Ksp = [Ag+][Br-]. Changes in ion concentration due to the addition of other substances can shift the equilibrium, affecting solubility.
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Solubility Product Constant
Common Ion Effect
The common ion effect refers to the decrease in solubility of a salt when a solution already contains one of the ions present in the salt. For example, adding HBr introduces Br- ions, which can shift the equilibrium of AgBr dissolution to the left, reducing its solubility. This principle is crucial for understanding how the addition of certain substances can impact the solubility of AgBr.
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Complex Ion Formation
Complex ion formation occurs when metal ions bind with ligands to form a more stable complex. In the case of AgBr, the addition of NH3 can lead to the formation of the complex ion [Ag(NH3)2]+, which effectively reduces the concentration of free Ag+ ions in solution. This shift can increase the solubility of AgBr by driving the dissolution equilibrium to the right, allowing more AgBr to dissolve.
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Related Practice
Textbook Question
Is the solubility of Zn(OH)2 increased, decreased, or unchanged on addition of each of the following substances? Write a balanced net ionic equation for each dissolution reaction. (See Appendix C.6 for formulas of complex ions.) (a) HCl
Textbook Question
Is the solubility of Zn(OH)2 increased, decreased, or unchanged on addition of each of the following substances? Write a balanced net ionic equation for each dissolution reaction. (See Appendix C.6 for formulas of complex ions.) (b) KOH