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| The chemical reactions are represented by simple chemical equations. The reaction at the positive plate is |

| PbO2 + H2SO4 = PbSO4 + H2O + O |

| The reaction at the negative plate is |

| Pb + H2SO4 = PbSO4 + 2H |

| Note the formation of gaseous oxygen (O) and hydrogen (2H). Although some of these gases react to form water (H2O), some escape into the atmosphere and represent a combustible and possible explosive mixture of the two, for which possibility precautions should be taken. The combined reactions at the two plates are as follows: |

| PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O |

| Figure 15-3 Chemical actions of lead-acid cell: (A) Discharging, (B) discharged, |

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