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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 of sodium acetylsalicylate is roughly 120 g per 100 mL of water, what is the approximate molar concentration of the saturated NaC₉H₇O₄ solution used in the reaction?

Question

Quizplus · Accepted Answer

11ecba2d_11cb_b4da_a3bf_1b32ff42b841_MD0008_00 A saturated solution contains the maximum amount of a compound that will dissolve in a given volume of solvent under the given conditions. Solubility measurements are often stated as the mass of compound that will dissolve per 100 g of solvent. For water (density = 1 g/mL) as a solvent, this can be expressed as 100 mL. Applying unit conversions, the concentration of a saturated solution can be expressed in units of molarity, which is defined as moles of solute per liter of solvent (mol/L). At saturation, the NaC₉H₇O₄ solution contains 120 g of NaC₉H₇O₄ in every 100 mL of water. This ratio equates to a concentration of 1.20 g/mL. To convert this into molarity, the volume must be converted from milliliters to liters (1000 mL = 1 L), and the mass (grams) must be converted into moles using the molar mass of NaC₉H₇O₄ (202.2 g/mol). Multiplying 1.2 g/mL by the volume conversion and dividing the grams by the molar mass yields a saturating molarity of 5.9 mol/L. (Choice A) A value of 0.006 M results from converting the mass to moles but failing to convert the unit of volume from milliliters to liters. This gives units of mol/mL instead of mol/L. (Choice B) A value of 0.59 M results from converting the mass to moles but failing to divide by the volume of the solution. This gives units of moles rather than mol/L. (Choice D) A value of 1200 M results from converting the volume from milliliters to liters but failing to convert the mass to moles. This gives units of g/L, not mol/L. Educational objective: A saturated solution contains the maximum amount of compound that will dissolve in a given volume of solvent under the given conditions. Solubility (expressed as grams of solute per 100 g of solvent) can be stated in units of molarity (moles of solute per liter of solvent) using unit conversions and the molar mass of the solute.

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