ALchem simple balance equation

2011-01-02 6:13 am

balance equation問題:
NO3-(aq) --> NO(g)

我寫左:
2H2O + 3e- + NO3- --> NO + 4 OH-

書的ans:
NO3- + 3e- + 4H+ --> NO +2H2O

我錯?
why?

回答 (2)

不用客氣

2011-01-02 7:41 am

✔ 最佳答案

The following equation is wrong:
2H2O + 3e⁻ + NO3⁻ → NO + 4OH-
This is because NO3⁻ ion CANNOT act as an oxidizing agent in neutral solutions or alkaline solutions. ONLY dilute HNO3 or NO3⁻ ion in dilute acid can act and an oxidizing and is reduced to give NO gas. Therefore, the correct equation should be :
NO3⁻ + 3e⁻ + 4H⁺ → NO + 2H2O

The following equation is also wrong:
7H⁺ + 8e⁻ + NO3⁻ → NH4⁺ + 3OH⁻
When an acid (H⁺) is used as the reaction, an alkali (OH⁻) will NEVER be one of the products.

參考: micatkie

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知識就是力量

2011-01-02 6:19 am

My guess:
These reactions are performed in acidic medium.
So product wont give OH^- as it is in alkaline medium.

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