Question

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?
(A)-Metal nitrates are unstable
(B)- Metal nitrates are highly soluble in water
(a)- A is false but B is true
(b)- A is true but B is false
(c)- A and B are true
(d)- A and B are false

Answer 1

Some of the commonly known nitrates are sodium nitrate and potassium nitrate. They can be found in nature as nitrate form and they can be mixed in water.

Complete answer:
We get metals commercially from the ores of respective metals. But in the ores, metals are combined with many other elements from which the metals by stepwise step process are extracted profitably. The metals are usually combined as oxides, carbonates, sulfates, sulfides, etc, but they are not usually found as nitrates.
We are given two statements here: (A)-Metal nitrates are unstable
(B)- Metal nitrates are highly soluble in water
So, statement A is false, because (A)-Metal nitrates are unstable
(B)- Metal nitrates are highly soluble in water
The statement A is false because the metal nitrates like sodium nitrate and potassium nitrate having formula $NaN{{O}_{3}}$ and $KN{{O}_{3}}$ are stable. That means they can be found as such in nature.
The statement B is true because the metal nitrates like sodium nitrate and potassium nitrate having formula A is false but B is true$NaN{{O}_{3}}$ and $KN{{O}_{3}}$ are highly soluble in water. Due to this high solubility, they are easily washed away by the rainwater and get dissolved in the water, which prevents them from forming ores.

Therefore, the correct answer is an option (a)- A is false but B is true.

Note:
$NaN{{O}_{3}}$ which is nitrate of the metal is also known as Chile saltpeter and commercially this salt is used for the extraction of sodium metal. The solubility of sodium nitrate in water is 91.2 g and the solubility of potassium nitrate is 383 g.