Solubility Homework Set Worked Out Solutions

Solubility Homework Set Worked Out Solutions

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Unformatted text preview: solubility of Sn(OH)2 in water in grams/liter? 2.6 x 10‐7 g/L 3 Dr. Fus CHEM 123 15. What is the solubility of iodide ions in a saturated solution of lead (II) iodide (Ksp = 1.4 10‐8)? Be careful! This question asks for the solubility of iodide ions, not necessarily that of the ionic compound. ____Pb2+(aq) + 2I‐(aq) PbI2(s) Initial ‐‐‐‐‐ 0 M 0 M Change ‐‐‐‐‐ +1x M +2x M Equilibrium ‐‐‐‐‐ +x M +2x M Ksp=[ Pb2+] [I‐]2= (x)(2x)2= 4x3= 1.4 x 10‐8 x= 1.5 x 10‐3 M HOWEVER, this is NOT the final answer because, according to the ICE table, the equilibrium concentration (solubility) of iodide ions in the saturated solution is 2x: 2x=2(1.5 x 10‐3 M)= 3.0 x 10‐3 M 16. Which compound is the least soluble (mol/L) in water? (a) CaCO3 Ksp = 2.8 x 10–9 (b) PbI2 Ksp = 8.7 x 10–9 (c) AgBr Ksp = 5.0 x 10–13 (d) Fe(OH)2 Ksp = 8.0 x 10–16 (e) Co(OH)2 Ksp = 1.6 x 10–15 You can directly compare solids with the same ratio of cation to anion (i.e. higher Ksp, more soluble) to eliminate some possible answer choices. However, if the ratios differ, the molar solubility (x) for EACH compound must be calculated using an ICE table because the lowest Ksp does not necessarily correspond to the lowest molar solubility. (a) 5.29 x 10‐5 mol/L (b) 1.30 x 10‐3 mol/L (c) 7.07 x 10‐7 mol/L (d) 5.85 x 10‐6 mol/L (e) 7.37 x 10‐6 mol/L Of these values, (c) is the lowest. So AgBr is the least soluble (even though its Ksp is not the lowest). 17. Which of the following salts has the highest concentration of silver ion when dissolved in water? AgCl Ksp = 1.6 x 10‐10 Ag2CO3 Ksp = 8.1 x 10‐12 AgBr Ksp = 5.0 x 10‐13 Calculate the molar concentration of silver ion for each of the salts. (a) 1.26 x 10‐5 M (b) 2.53 x 10‐4 M (make sure to multiply x by 2!) (c) 7.07 x 10‐7 M Of these concentrations, (b) is the highest. So Ag2CO3 has the highest concentration of silver ion (Note: this is not just because silver has a subscript of 2 after it in Ag2CO3; you must calculate the actual concentration for each compound). 4 Dr. Fus CHEM 123 18. Which compound is least soluble in water? Ksp = 1.6 x 10‐15 a) Co(OH)2 b) Fe(OH)2 Ksp = 8.0 x 10‐16 c) AgBr Ksp = 5.0 x 10‐13 d) CaCO3 Ksp = 2.8 x 10‐9 Ksp = 8.7 x 10‐9 e) PbI2 Make sure to calculate molar solubility and not to merely compare Ksp values if the ion ratios diffrer. (a) 7.37 x 10‐6 mol/L (b) 5.85 x 10‐6 mol/L (c) 7.07 x 10‐7 mol/L (d) 5.29 x 10‐5 mol/L (e) 1.30 x 10‐3 mol/L Of these values, (c) is the lowest. So AgBr is the least soluble. Qualitative Analysis Group I (Section 17.7 & “Isolation and Characterization of Metal Ions: Exploitation of Differences in Solubility” Lab) 19. An aqueous solution contains the following twelve ions: Zn2+, Co2+, Pb2+, Ni2+, Cu2+, Sn2+, Fe2+, Sb3+, Al3+, Cr3+, Bi3+, and Ag+ and cold dilute HCl is added. What precipitate(s) will form? Look at the solubility rules. All chloride salts are soluble EXCEPT those with Ag+, Hg2+, and Pb2+. Therefore, of the cations listed, PbC...
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This homework help was uploaded on 03/28/2014 for the course CHEM 123 taught by Professor Larosa during the Spring '06 term at Ohio State.

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