题目

Black beautyMy first home was a beautiful meadow with a pound of clear water. There were some large trees near the pond. On one side of the meadow was a field and on the other was the house of our master, Farmer Grey. He was a kind man.My mother and I had a happy life. She worked during the day. I played with the other young horses and had great fun. At night I lay next to her.One day, my master sold me to Squire Gordon. He lived with his family in a big house.“You are a beautiful horse,” he said, “You have a beautiful black coat. I shall call you Black Beauty.”I learned to carry my ma铅蓄电池是典型的可充型电池，它的正负极格板是惰性材料，电池总反应式为：Pb＋PbO2＋4H+＋2SO42-2PbSO4＋2H2O 请回答下列问题（不考虑氢、氧的氧化还原）：（1）放电时：正极的电极反应式是_______________；电解液中H2SO4的浓度将变__________；当外电路通过1mol电子时，理论上负极板的质量增加__________g。（2）在完全放电耗尽PbO2和Pb时，若按上图连接，电解一段时间后，则在A电极上生成__________、B电极上生成__________，此时铅蓄电池的正负极的极性将__________。