Sunday, September 29, 2013

Colour of Nitric acid

Question: Why does concentrated nitric acid trun yellow brown upon long standing?

Answer: Nitric acid (HNO3) is colourless in pure form. But it tends to acquire yellow brown colour as it become older. This is because it is a highly strong mineral acid. Due to this, it decomposes easily into oxides of nitrogen (NO2), oxygen and water.



The produced nitrogen oxides dissolve partly or completely in the acid and give yellow or even red colour at higher temperatures. 

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