Questions and Answers
What is the effect of adding a soluble salt that contains one of the ions of the slightly soluble salt on the solubility of the slightly soluble salt?
What happens to the equilibrium when Pb2+ is added to the solubility equilibrium of solid PbCrO4?
What is the unit of molar solubility?
What is the solubility product for calcium oxalate?
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What is the effect of the common-ion effect on the solubility product of the slightly soluble salt?
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Why does the addition of Pb(NO3)2 to the solubility equilibrium of solid PbCrO4 decrease the solubility of PbCrO4?
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What is the purpose of calculating the molar solubility of a slightly soluble salt?
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What is the condition necessary for the common-ion effect to occur?
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What is molar solubility in the context of a saturated solution?
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Under what condition can the Ksp values of different compounds be meaningfully compared?
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What does the Ksp represent for a compound like calcium oxalate in a saturated solution?
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If a saturated solution of calcium oxalate produces a residue of 0.0061 g after evaporation, what information can be calculated?
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What is the molar solubility of calcium oxalate calculated from a 0.0061-g residue?
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If 1.2 x $10^{-3}$ mol of lead(II) iodide dissolves in 1 L of solution, what does this information imply about its solubility product constant?
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Why might Ksp values not always be directly compared between different compounds?
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In the context of solubility, what does the residue left after evaporation of a saturated solution represent?
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What condition must be met for precipitation to occur in a solution?
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What does it mean if Q equals Ksp in a solution?
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If the ion product Q is less than Ksp, what is the state of the solution?
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What is the significance of the ion product in solubility reactions?
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What happens to a solution when Q is greater than Ksp?
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In a solubility reaction, what does the term Ksp represent?
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If the concentrations of ions in a solution are equal to 0.15 M each, and Ksp is known to be $2.3 imes 10^{-9}$, what can be inferred?
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Why is the ion product referred to as the ion product instead of the reaction quotient?
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What does the solubility product constant (Ksp) represent in the context of ionic compounds?
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In the dissociation reaction of a slightly soluble ionic compound M𝑝X𝑞, which expression represents the solubility product?
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When calculating molar solubility, what must be taken into account if the coefficients of the ions differ?
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What relationship can be inferred if a compound is classified as insoluble in water?
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Which of the following salts' dissociation expression corresponds to the Ksp: Ksp = [Ca][F]2?
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What happens to the Ksp value as the solubility of a compound increases?
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In the context of molar solubility, what does the term 'molar solubility' specifically refer to?
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What does the notation M𝑝X𝑞 signify in a dissociation reaction?
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What happens to the solubility of insoluble ionic hydroxides as the pH increases?
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Which statement describes selective precipitation?
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How does lowering the pH affect the solubility of ionic compounds containing anions of weak acids?
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In fractional precipitation, what is essential for a reagent to be effective?
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Which of the following statements is true about the relationship between pH and ion concentration in a solution containing ionic hydroxides?
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What is the effect of adding H3O+ to a solution containing carbonate ions (CO32−)?
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Study Notes
Solubility Equilibria
- All ionic compounds dissolve in water to some degree, but many have low solubility and are classified as insoluble.
- The equilibrium constant Ksp can be used to determine the relative solubilities of salts in water.
Solubility Product Constant (Ksp)
- Ksp is the equilibrium constant for the solubility equilibrium of a slightly soluble (or nearly insoluble) ionic compound.
- It represents the dissociation of a solid salt into its aqueous ions.
- The solubility product expression is: Ksp = [Mm+]p [Xn−]q
Molar Solubility (s)
- Molar solubility is the number of moles of solute that will dissolve in a liter of solution.
- It is related to Ksp and represents the molarity of the dissolved solute in a saturated solution.
- Ksp values of compounds cannot always be compared, and the compounds must have the same dissociation stoichiometry.
Example Calculations
- Calculate the molar solubility of CaC2O4 given Ksp and residue mass.
- Calculate the solubility product constant of PbI2 given experimental data.
Solubility and the Common-Ion Effect
- Addition of a soluble salt that contains one of the ions of the slightly soluble salt decreases the solubility of the slightly soluble salt.
- This is because the added ion shifts the equilibrium to the left.
Precipitation
- Precipitation occurs when the concentrations of the ions exceed the solubility of the ionic compound.
- Compare the ion product, Q, to Ksp to determine if precipitation will occur:
- Q = Ksp: saturated solution, no precipitation.
- Q < Ksp: unsaturated solution, no precipitation.
- Q > Ksp: supersaturated solution, precipitation will occur.
Fractional Precipitation
- This technique is used to separate two or more ions from a solution by adding a reactant that precipitates first one ion, then another.
- A successful reagent can precipitate with more than one cation if their Ksp values are significantly different.
Effect of pH on Solubility
- For insoluble ionic hydroxides, higher pH decreases solubility, and lower pH increases solubility.
- For insoluble ionic compounds containing anions of weak acids, lower pH increases solubility.
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Description
Understanding solubility of ionic compounds in water and the solubility product constant (Ksp) that determines their relative solubilities.