CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Aluminum sulfate, Al₂(SO₄)₃, is dissolved in water to create an aqueous solution that will be represented by a particle-level diagram.
A student begins with an empty 3-cm-by-3-cm square "box" and intends to show exactly six sulfate ions in that fixed volume.
(a) Determine the number of aluminum ions that must be placed in the box so that the diagram reflects complete dissociation and overall charge neutrality.
(b) Suppose a second diagram is drawn for a different solution in which the concentration of Al₂(SO₄)₃ is doubled while the box volume remains 3 cm × 3 cm. Describe quantitatively how the counts of each ion would change relative to the first diagram.
(c) Explain why it would be incorrect to depict the sulfate species as separate S6+ and O2− ions in this context.
(d) Identify one common student error when drawing the hydration shell around SO₄²⁻ ions, and describe how to avoid the error.