Textbook Question
Calculate the molar solubility of Cr(OH)3 in 0.50 M NaOH; Kf for Cr(OH)4- is 8 x 10^29.
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Ch.17 - Applications of Aqueous Equilibria
Chapter 17, Problem 128
Hard water contains alkaline earth cations such as Ca2+, which react with CO32- to form insoluble deposits of CaCO3. Will a precipitate of CaCO3 form if a 250 mL sample of hard water having [Ca2+] = 8.0 x 10^-4 M is treated with the following? (a) 0.10 mL of 2.0 x 10^-3 M Na2CO3 (b) 10 mg of solid Na2CO3
Verified step by step guidance1
Step 1: Calculate the moles of Ca^{2+} in the 250 mL sample of hard water using the concentration [Ca^{2+}] = 8.0 \times 10^{-4} \text{ M}.
Step 2: For part (a), calculate the moles of CO_3^{2-} added by using the volume (0.10 mL) and concentration (2.0 \times 10^{-3} \text{ M}) of Na_2CO_3 solution.
Step 3: For part (b), convert the mass of Na_2CO_3 (10 mg) to moles using its molar mass, and then determine the moles of CO_3^{2-} provided.
Step 4: Determine the reaction quotient Q_{sp} for the potential formation of CaCO_3 using the concentrations of Ca^{2+} and CO_3^{2-} in the solution.
Step 5: Compare Q_{sp} to the solubility product constant K_{sp} of CaCO_3. If Q_{sp} > K_{sp}, a precipitate will form; if Q_{sp} < K_{sp}, no precipitate will form.
Related Practice
Open Question
Zinc hydroxide, Zn(OH)2 (Ksp = 4.1 x 10^-17), is nearly insoluble in water but is more soluble in strong base because Zn2+ forms the soluble complex ion [Zn(OH)4]2- (Kf = 3 x 10^15). (a) What is the molar solubility of Zn(OH)2 in pure water? (You may ignore the OH- from the self-dissociation of water.) (b) What is the pH of the solution in part (a)? (c) What is the molar solubility of Zn(OH)2 in 0.10 M NaOH?
Textbook Question
Citric acid (H3Cit) can be used as a household cleaning agent to dissolve rust stains. The rust, represented as Fe(OH)3, dissolves because the citrate ion forms a soluble complex with Fe3+
(a) Using the equilibrium constants in Appendix C and Kf = 6.3 x 10^11 for Fe(Cit), calculate the equilibrium constant K for the reaction.
(b) Calculate the molar solubility of Fe(OH)3 in 0.500 M solution of H3Cit.
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Open Question
The pH of a sample of hard water having [Mg2+] = 2.5 x 10^-4 M is adjusted to pH 10.80. Will Mg(OH)2 precipitate?
Open Question
In quantitative analysis, Al3+ and Mg2+ are separated in an NH4+ - NH3 buffer having pH approximately equal to 8. Assuming cation concentrations of 0.010 M, show why Al(OH)3 precipitates but Mg(OH)2 does not.
Textbook Question
Can Fe2+ be separated from Sn2+ by bubbling H2S through a 0.3 M HCl solution that contains 0.01 M Fe2+ and 0.01 M Sn2+? A saturated solution of H2S has [H2S] ≈ 0.10 M. Values of Kspa are 6 x 10^2 for FeS andd 1 x 10^-5 for SnS.
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