question_answer

"Metals are usually not found as nitrates in their ores". Out of the following two (a and b) reasons which is/are true for the above observation?

I. Metal nitrates are highly unstable. [NEET 2015 ]

II. Metal nitrates are highly soluble in water.

A) I and II are true

B) I and II are false

C) I is false but II is true      

D) I is true but II is false

Correct Answer: C

Solution :

[c] Metals are usually not found as nitrates in their ores, because metal nitrates are highly, soluble in water. For example, \[KN{{O}_{3}}\] (salt peter) would be classified as completely soluble. Thus, \[KN{{O}_{3}}\] could be expected to dissociate completely in aqueous solution into \[{{K}^{+}}\]and \[NO_{3}^{-}\] ions

\[KN{{O}_{3}}{{K}^{+}}(aq)+NO_{3}^{-}(aq)\]

The nitrate anion has three equivalent oxygen surrounding a central nitrogen atom. This tends to spread the single negative charge and make it easier for water (using hydrogen bonds) to separate the ions in solution.