Two students independently attempt to depict a particle-level diagram for a 0.20 M…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Two students independently attempt to depict a particle-level diagram for a 0.20 M aqueous solution of potassium sulfate, K₂SO₄. Their verbal descriptions are given below.
• Diagram A: "I placed twice as many K⁺ ions as SO₄²⁻ ions, scattered uniformly. Around each SO₄²⁻ ion I drew the oxygen atoms of several water molecules pointing toward the ion. Around each K⁺ ion I drew the oxygen atoms pointing away."
• Diagram B: "I kept every formula unit intact, drawing K₂SO₄ as a single cluster surrounded by water molecules. I oriented the water molecules randomly because the compound is overall neutral."
Assume the solution volume represented by both diagrams is the same.
(a) Identify which diagram more accurately represents the solution at the particulate level.
(b) Cite two specific features from the more accurate diagram that make it consistent with the expected behavior of K₂SO₄ in water.
(c) For the less accurate diagram, describe two modifications that must be made to correct it.
(d) Explain why the polyatomic ion in K₂SO₄ must remain intact in the correct representation, even though the compound dissociates completely.