Final answer:
The balanced chemical equation for the reduction-oxidation reaction between potassium and chromium ions, with phase notations, is K(s) + Cr3+(aq) → Cr(s) + K+(aq).
Step-by-step explanation:
The chemical equation provided by the student, K(s) + Cr3+(aq) → Cr(s) + K+(aq), expresses a redox (reduction-oxidation) reaction where elemental potassium (K) is oxidized to potassium ions (K+) and chromium ions (Cr3+) are reduced to elemental chromium (Cr). Identifying the phases in this reaction: elemental potassium is a solid (s), chromium ions are in an aqueous solution (aq), elemental chromium is a solid (s), and potassium ions are in an aqueous solution (aq). The balanced chemical equation with phase notations would be K(s) + Cr3+(aq) → Cr(s) + K+(aq).