# pH Changes in primary cells

Primary Cells - pH changes during discharge

Alkaline Cell:

Manganese Dioxide Zinc Alkaline Cell

Anode (-) $\ce {Zn(s) + 2OH^{−}(aq) → ZnO(s) + H2O(l) + 2e^{−}}$

Cathode (+) $\ce {2MnO2(s) + H2O(l) + 2e^{−} → Mn2O3(s) + 2OH^{−}(aq)}$

Overall $\ce {Zn(s) + 2MnO2(s) → ZnO(s) + Mn2O3(s)}$

• $\ce {OH-}$ ions are consumed at the anode
• $\ce {OH-}$ ions are formed at the cathode
• $\ce {same[OH^{−}]}$
• pH - no change

Is this correct? Do pH changes occur during the discharge process?

## 1 Answer

No, the reaction does not produce hydroxide ions. But the solution is already basic (probably between pH 12 and 14).

• I fixed your edits - because I wrote it wrong at first... or have I corrected it incorrectly? Can you take a look again? Sep 7 '14 at 2:47
• So was my answer.
– LDC3
Sep 7 '14 at 2:48
• so there is no change - but the solution remains basic? Sep 7 '14 at 2:50
• Yes, the solution remains basic.
– LDC3
Sep 7 '14 at 2:55