Passage
Although acetylsalicylic acid (aspirin) is a well-known and widely used analgesic and anti-inflammatory agent, copper(II) acetylsalicylate, a copper complex formed from aspirin and copper, has also been found to exhibit some distinctive and potentially beneficial pharmacological properties. Formation of copper(II) acetylsalicylate is achieved when the conjugate base of aspirin, acetylsalicylate (C₉H₇O₄⁻) , binds to Cu²⁺ ions in solution, as outlined in Reaction 1.4 NaC₉H₇O₄(aq) + 2 CuSO₄(aq) → Cu₂(C₉H₇O₄) ₄(s) + 2 Na₂SO₄(aq) Reaction 1Using Reaction 1, a researcher synthesized a sample of copper(II) acetylsalicylate for analysis. A small volume of 0.50 M aqueous copper(II) sulfate (molar mass = 159.6) was mixed into 100 mL of filtered, saturated aqueous sodium acetylsalicylate (molar mass = 202.2) at room temperature and slowly stirred. Formation of copper(II) acetylsalicylate (molar mass = 843.7) was immediately observed as a bright blue precipitate. The precipitate was then isolated by filtration and dried, affording the product complex in high yield.
Adapted from: Seguel GV, Rivas BL, Contreras JG. Synthesis and characterization of copper complexes: interaction of metalliccarboxylates with 1,3-thiazole ligand. Journal of the Chilean Chemical Society. 1970; 58(4) :1967.
-If the solubility product constant K_sp for NaC₉H₇O₄ is estimated to be 34.9, what is the approximate acetylsalicylate ion concentration in the saturated NaC₉H₇O₄ solution used for the reaction?

Question

Quizplus · Accepted Answer

11ecba2d_11cd_628d_a3bf_bdcd10fbdf70_MD0008_00 For the dissolution of compound Z into ions X and Y, a general dissolution reaction can be written as: 11ecba2d_11cd_628e_a3bf_0d19bfade3c3_MD0008_00 From the general dissolution reaction above, an equilibrium constant associated with the dissolution process can be written to give the solubility product constant K_sp: 11ecba2d_11cd_628f_a3bf_c1d062e64e60_MD0008_00 In the K_sp expression, [X] and [Y] are the molar concentrations of the X and Y ions, and c and d are the respective coefficients of the balanced dissolution reaction. The K_sp is the product of the maximum concentrations of each ion possible in the solution under the given conditions. As a result, the K_sp correlates to the limit of solubility for the compound (a saturated solution). For the dissociation of NaC₉H₇O₄, which releases one Na⁺ ion and one C₉H₇O₄⁻ ion, K_sp = [Na⁺][C₉H₇O₄⁻]. Because 1 mole of Na⁺ and 1 mole of C₉H₇O₄⁻ are released into solution for each mole of NaC₉H₇O₄ that dissociates, [Na⁺] and [C₉H₇O₄⁻] are always equal. Therefore, the concentration of the acetylsalicylate ion in a saturated solution is equal to the square root of the K_sp: 11ecba2d_11cd_6290_a3bf_2f49d4f45597_MD0008_00 11ecba2d_11cd_6291_a3bf_77408994e343_MD0008_00 Here, it is unnecessary to perform a rigorous manual calculation of the square root of 34.9. Instead, the correct answer can be identified by approximation. Because 5² = 25, and 6² = 36, the square root of 34.9 must be between 5 and 6. (Choice A) 2.95 M is half of the molar concentration of the C₉H₇O₄⁻ ion. In the saturated solution, both the Na⁺ ion and the C₉H₇O₄⁻ ion have a concentration of 5.91 M. The calculation does not require dividing the result in half. (Choice C) 17.4 M is obtained if the K_sp is divided in half rather than taking the square root. (Choice D) 34.9 is the value of the K_sp rather than the concentration of the C₉H₇O₄⁻ ion. Educational objective: The solubility product constant K_sp represents the limit of solubility for a compound, and it is defined as the product of the molar concentrations of the dissolved species each raised to the power of their respective balanced equation coefficients. This relationship can be used to find molar concentrations of ions in saturated solutions.

Passage Although Acetylsalicylic Acid (Aspirin) Is a Well-Known and Widely Used