为什么Al电极在原电池中的化学式是Al-3e+4OH-=AlO2-+2H2O

2024年11月20日 02:34
有4个网友回答
网友(1):

分析本题条件可知,该题中只有AL与NaOH发生反应,所以AL作负极,Mg应该作正极。则负极反应可以分两步思考:第一步,Al-3e=Al3+。第二步,Al3+与NaOH发生反应:
Al3+ + 4OH-=AlO2-+2H2O。两步综合起来思考,将第一步与第二步相加就得
Al-3e+4OH-=AlO2-+2H2O。各项都乘以2可以得负极总反应:2Al-6e+8OH-=2AlO2-+4H2O。而正极反应可以写成6H2O+6e=6OH- +3H2,将负极总反应与正极反应相加得
2Al+2OH-+2H2O=2AlO2- + 3H2 。同学如果明白了记得给一个鼓励,谢谢!

网友(2):

这是因为在原电池中,Al是先失去3电子,变成铝离子,而三价的铝离子跟过量的氢氧根反应,生成偏铝酸根。因为电解质溶液中含有的氢氧根量绝对比铝离子多,所以这道题把氢氧根离子看作过量,生成偏铝酸根,如果是适量的话,则会生成氢氧化钠,所以实质上,那个化学是两部分反应的结合,而下面的那个化学方程式是铝做为金属时与氢氧化钠的反应!!具体反应如下:
Al-3e=Al3+
Al3++4OH-=AlO2-+2H2O
把这两个结合就是你要的原电池中反应的化学方程式

网友(3):

抵消了一部分

Mg、Al 、NaOH溶液为电解质溶液,只有Al和NaOH溶液反应,所以Al为负极
两极反应: (要保证正负极得失电子相等)
负极 2 Al - 6e- + 8 OH- = 2 AlO2- + 4 H2O
正极 6 H2O + 6 e- = 3 H2↑ + 6 OH-
总反应 2 Al + 2 OH- + 2 H2O = 2 AlO2- + 3 H2 ↑

负极消耗8 OH-,正极产生6 OH-,总反应相当于消耗2 OH-
所以总反应中NaOH的化学计量数是 2

网友(4):

如果不要求正负极反应同时写,而是只写一个的话,电极反应是应写最简,而不是和总反应计量数相同~

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