Question

Which half-reaction correctly describes an oxidation?
Upper C a (s) plus 2 e superscript minus right arrow upper C a superscript 2 plus (a q).
Upper B r subscript 2 plus 2 e superscript minus right arrow 2 upper B r superscript minus.
Upper N a superscript plus (a q) right arrow upper N a (s) plus e superscript minus.
Upper C r (s) right arrow upper C r superscript 3 plus (a q) plus 3 e superscript minus.

Answer 1

Oxidation is loss of electrons (electrons appear on the product side). The correct oxidation half-reaction is:

Cr(s) → Cr³⁺(aq) + 3 e⁻

(The others either show electrons on the reactant side (reductions) or are written with incorrect directions/charges.)