A reaction vessel initially contains aqueous calcium ions (depicted as yellow spheres…
CHEMISTRY · Multi-part · AP · Chemistry · Chemical Reactions · Chemical Reactions
Problem
A reaction vessel initially contains aqueous calcium ions (depicted as yellow spheres labeled Ca²⁺) and aqueous sulfate ions (depicted as red tetrahedral clusters labeled SO₄²⁻). After some time, the particulate diagram of the vessel shows all of the following species:
• 6 Ca²⁺ ions solvated in the solution.
• 4 SO₄²⁻ ions solvated in the solution.
• An unidentified solid substance X forming a crystal lattice at the bottom of the vessel, represented by a repeating array of yellow spheres alternating with red tetrahedral clusters in a 3 : 2 ratio (three yellow clusters for every two red clusters).
No other ions are present.
Assume that only a single precipitation process has occurred and that charge and mass are conserved.
(a) Deduce the empirical formula of the solid substance X that has precipitated, based on its described lattice pattern.
(b) Propose the balanced net-ionic equation that accounts for the formation of X from the initial aqueous ions present. Clearly show states of matter.
(c) Using your equation from part (b), calculate how many calcium ions and sulfate ions must have combined to produce the amount of precipitate implied by the current particle counts in solution.
(d) Compare your calculated required amounts with the particle counts actually observed in the solution. Discuss whether the diagram is fully consistent with the law of conservation of charge and mass, and if not, explain the discrepancy and indicate what modifications to the diagram would correct it.