Question

A sodium salt on treatment with \[MgC{{l}_{2}}\] gives white precipitate only on heating. The anion of the sodium salt is-
A.\[HCO_{3}^{-}.\]
B.\[CO_{3}^{2-}.\]
C.\[NO_{3}^{-}.\]
D.\[SO_{4}^{2-}.\]

Answer 1

Hint: We know that the Salts that are produced by the reaction between a strong base and a strong acid are neutral in nature. The bonds formed between the anion and the cation are strong, and they do not break apart in solution.

Complete answer:
As we know that the salts formed from neutralization reactions between weak bases and strong acids are found to be acidic in nature. Ammonium chloride is an example of acidic salt. The ions when they are taken as sodium salts and how they react when silver nitrate is added to them and how they further react when dilute nitric acid is added to it.
Accordingly, if ions show all the same reactions, then it will take to form sodium salt and further it will carry the reaction in the same way as stated. This is so because the statement further states that when magnesium carbonate is added to the above solution then a white precipitate is obtained which further is undissolved in dilute carbon dioxide. So, when we look at the magnesium chloride. The salt will be sodium bicarbonate and the anion is \[HCO_{3}^{-}.\] When sodium bicarbonate react with \[MgC{{l}_{2}}\] it produce Magnesium bicarbonate which is also soluble in water But, on heating \[Mg{{\left( HC{{O}_{3}} \right)}_{2}}~\] it produce \[Mg\left( C{{O}_{3}} \right)~\] which gives white precipitate

Therefore, the correct answer is option A.

Note:
Remember that the salts resulting from the neutralization reaction between a weak acid and weak base can be mildly basic, mildly acidic, or neutral depending on the nature of the bases and acids involved. The degree of hydrolysis and ionization of water is independent of the concentration of the solution.