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).