Question

Ammonium silver nitrate solution is called:
A.reagent
B.Fehling solution
C.(A) and (B)
D.None of these

Answer 1

Hint: The alkaline solution of ammonium silver nitrate reacts with aldehydes to form carboxylic acid and metallic silver is formed which shines like a silver mirror. When it is reacted with ketones they do not react with it. Hence, Ammonium silver nitrate solution $\left[Ag{\left(N{H}_3\right)}_2\right]N{O}_3$ is used to distinguish between aldehydes and ketones.

Complete step by step answer:
Ammonium silver nitrate is a solution of silver nitrate and ammonia. It was named Tollen’s reagent after a German scientist Bernhard Tollens. It is used to test the aldehyde functional group .It has a short shelf- life hence it has to be prepared fresh for use. Its preparation is as follows-
In solution of silver nitrate, a few drops of sodium hydroxide is added and brown precipitate of silver oxide is obtained. The reaction is as follows-
$2AgN{O}_3+2NaOH\to \underset{\text{brown ppt}.}{A{g}_{2}O}+2NaN{O}_3+H_{2}O$
This brown ppt. is then dissolved in ammonia to obtain ${\left[Ag{\left(N{O}_3\right)}_2\right]}^{+}$ complex.This complex is known as Tollen;s reagent.

$\underset{\text{brown ppt}.}{A{g}_{2}O}+2NaN{O}_3+H_{2}O+4N{H}_3\to 2\left[Ag{\left(N{O}_3\right)}_2\right]N{O}_3+2NaOH$
When tollens reagent reacts with aldehyde, aldehyde is oxidized and forms carboxylic acid. The silver ions in tollen’s reagent convert to metallic silver which forms a silver mirror at the bottom of the test tube.This test is also known as silver mirror test.The reaction is –
$R-CHO+2A{g}^{+}+2^{-}OH\to R-COOH+2Ag+H_{2}O$

Hence the correct option is A.

Additional Information:
- Fehling solution is prepared by mixing cupric sulphate penta-hydrate solution and Rochelle salt (potassium sodium tartrate tetra-hydrate).
-It is also used to distinguish between aldehydes and ketones because aldehydes give positive results to the test.
-It is also used to determine monosaccharide and other reducing sugars.
-It is also used to detect glucose in urine for diabetic patients.
-It is used in breakdown of starch to glucose syrup and maltodextrins. Maltodextrins are polysaccharides used as food additives.

Note:
The uses of ammonium silver nitrate solution are-
-It is used to distinguish between aldehydes and ketones.
-It is used to apply a silver mirror to clean glassware.