Which of the following aqueous solutions of Na₂SO₄ is isotonic with a 0.15 M NaCl solution? A) 0.05 M B) 0.10 M C) 0.15 M D) none of these

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Quizplus · Accepted Answer

The key to solving this problem is to realize that isotonic solutions have the same concentration of solutes as a reference solution (in this case, 0.15 M NaCl). To determine which solution is isotonic with a 0.15 M NaCl solution, we need to calculate the molarity of NaCl in the given solution and see which solution has the same molarity of NaCl. To do this, we need to break down Na₂SO₄ into its constituent ions: Na+ and SO42-. NaCl also breaks down into its constituent ions: Na+ and Cl-. 0.15 M NaCl implies 0.15 M Na+ and 0.15 M Cl-. Since Na₂SO₄ contains only Na+ and SO42- ions, and we know that the concentration of Na+ ions in the isotonic solution must match 0.15 M of Na+ ions in 0.15 M NaCl, the total concentration of Na+ ions in the isotonic solution must be 0.15 M. The concentration of Na+ ions in a 0.05 M Na₂SO₄ solution is (0.05 M) x (1 mole of Na+/1 mole of Na₂SO₄) = 0.05 M Na+. The concentration of Na+ ions in a 0.10 M Na₂SO₄ solution is (0.10 M) x (1 mole of Na+/1 mole of Na₂SO₄) = 0.10 M Na+. The concentration of Na+ ions in a 0.15 M Na₂SO₄ solution is (0.15 M) x (1 mole of Na+/1 mole of Na₂SO₄) = 0.15 M Na+. Since the concentration of Na+ ions in a 0.15 M Na₂SO₄ solution matches the 0.15 M concentration of Na+ ions in 0.15 M NaCl, (C) 0.15 M is the correct choice. However, (B) 0.10 M also works because its concentration of Na+ ions matches that of the NaCl solution.

Which of the Following Aqueous Solutions of Na2SO4 Is Isotonic

Which of the Following Aqueous Solutions of Na₂SO₄ Is Isotonic