Balance the half reaction, c5o5 2-(g) â co3 2-(aq), taking place in basic media. which answer below describes how many hydroxide ions are needed to balance the half reaction?

Answer is: 20 ions, left side.

Unbalanced half reaction: C₅O₅²⁻(g) → CO₃²⁻(aq).

1) There are 5 carbon atoms on the left side of half reaction and 1 carbon atom on right, so first add coefficient 5 in fron of carbon dioxide to balance carbon atoms: C₅O₅²⁻(g) → 5CO₃²⁻(aq).

2) Because there are more oxygen atoms on the right, add OH⁻ ions on the left side of half reaction and water on the right: OH⁻(aq) + C₅O₅²⁻(g) → 5CO₃²⁻(aq) + H₂O(l).

3) Balance oxygen (25 atoms on boths side) and hydrogen (20 atoms on both side of half reaction) atoms:

Balanced half reaction: 20OH⁻(aq) + C₅O₅²⁻(g) → 5CO₃²⁻(aq) + 10H₂O(l).