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

• A

  a and b are true
• B

  a and b are false
• Correct answer
  C

  a is false but b is true
• D

  a is true but b is false

Solution

Metals are usually not found as nitrates in their ores, because metal nitrates are highly soluble in water. 

The nature anion $\left(N{O}_3^{-}\right)$ has three equivalent oxygen surrounding a central nitrogen atom. This tends to spread the single negative charge and make it easier for water to separate the ions in solution.

Hence, the correct answer is option: 'C'.