题干

 在化学反应中,凡是元素化合价发生改变的反应,称为氧化还原反应.配平这类反应方程式往往采用“化合价升降法”更方便快捷,即反应中元素“化合价升高总数=化合价降低总数”.
例如:□Al+□MnO2═□Al2O3+□Mn,具体配平步骤如下:
①“标变价”:找出化合价发生改变的元素,并标出改变前后的化合价.
4Al0+3Mn+4O2═2Al2+3O3+3Mn0
②“列变化”:列出改变的价态数.
Al0→Al+3 升高3价 Mn+4→Mn0降低4价
③“找倍数”:找出化合价升、降的最小公倍数为3×4=12,从而确定Al、MnO2的系数.
4Al+3MnO2═2Al2O3+3Mn
④“配系数”:再用观察法,配平其它系数.
4Al+3MnO2═2Al2O3+3Mn
根据以上信息,结合已学知识,回答下列问题:
上一题 下一题 0.0难度 选择题 更新时间:2017-05-20 08:21:30

答案(点此获取答案解析)

同类题1

阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项。

    Gwondo was a trainer of dogs. He would go out every day with his dogs, to1 them how to catch animals so all his tribe(部落) could eat.

    Wherever Gwondo went, his tribe could see him away in the distance  2 his white hair would shine in the sunlight. The tribe 3would say to their children, "See, there is Gwondo and his dogs, searching for 4 for us all. " Gwondo went out hunting every day and always came 5 with much food. And all were very happy.

    Now Gwondo grew 6 and as all humans do, one day he died. The tribe felt sad and cried many days and many nights 7 one day the elders called to their children, " You have cried enough for Gwondo. Now it is time to 8 living. Go down to the beach and be happy."

    The children ran down to the beach and looked out to sea. 9, they all looked at each other, then turned and ran back to their elders, 10, "Come quickly. Gwondo, he is back with us. He is out in the sea. "The elders hurried to the 11 and said, "Yes! It is Gwondo back! He is now a dolphin and lives in the sea. "

    Now whenever you see 12 dolphins in the sea, look for the big old dolphin. You will know him because he has a large white fin on 13 back. He is Gwondo and he is training the young dolphins to chase(追逐) 14 close to the beach so that his tribe can catch them.

     Gwondo is known to all the tribes 15 the east coast of Australia. They call him their sea dog.