A student attempts to illustrate the reaction between aqueous sodium phosphate and…
CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
A student attempts to illustrate the reaction between aqueous sodium phosphate and aqueous aluminum nitrate to produce solid aluminum phosphate and aqueous sodium nitrate. The balanced molecular equation for the reaction is
Na₃PO₄(aq) + Al(NO₃)₃(aq) → AlPO₄(s) + 3 NaNO₃(aq)
The student’s particulate diagram of a reaction mixture that has supposedly gone to completion is described below.
• 4 solvated Na⁺ ions (blue spheres labeled “+”).
• 1 solvated PO₄³⁻ ion (purple tetrahedral cluster labeled "3–").
• 1 solvated Al³⁺ ion (silver sphere labeled “3+”).
• 3 solvated NO₃⁻ ions (green trigonal clusters labeled “–”).
• 1 solid unit of AlPO₄ (a silver sphere touching a purple tetrahedral cluster) present at the bottom of the container.
No other species are shown.
Critically analyze this diagram for consistency with both the balanced equation and the principles of mass and charge conservation.
(a) Determine the stoichiometrically correct ratios of all ionic and solid species that should be present after the reaction has gone to completion according to the balanced equation.
(b) Identify every mass-balance error in the student’s diagram by comparing the required numbers from part (a) with the particle counts depicted.
(c) Evaluate the diagram for overall charge balance. State the total charge that should reside in the solution phase and the total charge actually depicted, and explain any discrepancy.
(d) Provide a complete, itemized description of a corrected particulate diagram that accurately represents the reaction mixture at completion, clearly specifying the number and physical state of each distinct species.