An entrance JEE Main & Advanced AIEEE 2003 exam question:

Which one of the following nitrates will leave behind a metal on strong heating?

A. Copper nitrate
B. Manganese nitrate
C. Silver nitrate
D. Ferric nitrate

I looked up the answer and it was given to be silver nitrate, and I took it up as something to be remembered. However, when I checked online for the decomposition of other options such as ferric nitrate I found many research papers discussing the same which is not something one asks students who have just studied chemistry up to 12th grade.

Also, is there a way to decide which one will, because if it says strong heating, shouldn't most metals leave their salts and exist as free metals if we go on increasing temperature?


Most metal nitrates decompose on heating to give metal oxides. Decomposition of silver nitrate is different as it yields elemental silver. $$\ce{2AgNO3 -> 2Ag + O2 + 2NO2}$$ Usually the metals which lie very low in the activity series decompose to give their elemental form. I don't think it's possible to extract metals from just any nitrate by strong heating. They will yield their respective oxide which won't give the element rather they'll just fuse (melt) just like stable metal oxides like $\ce{Al2O3}$ does.


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