Question

A moisten salt is rubbed with oxalic acid between the fingers and smells like vinegar. It indicates the presence of:
A,.Sulphur
B.Nitrate
C.Nitrite
D.Acetate

Answer 1

Hint:Vinegar is a common name for the aqueous solution of one of the members of the carboxylic acid family and is produced by the fermentation of ethanol or sugar using a special type of bacteria.
Complete step by step answer:
Now in the given question there is an unknown salt which is rubbed with oxalic acid such that it leads to formation of a compound that smells like vinegar.
 As we all know that vinegar is an aqueous solution of acetic acid including trace chemicals for flavoring purpose. It contains $5 - 8\% $ of acid by volume and is prepared by using gram-negative bacteria which is capable of oxidizing ethanol into acetic acid
This means the compound which was formed after rubbing oxalic acid smelling like vinegar must be acetic acid
Furthermore we know that salts usually have two constitutes
a cation that carries positive charge
an anion that carries negative charge
 Now since all the options are types of anions this indicate the test that was carried out will also be that of an anion
Since only acetate ion on reaction with oxalic acid can lead to formation of acetic acid for which the chemical reaction is shown below
$HOOC - COOH + 2C{H_3}COONa \to NaOOC - COONa + 2C{H_3}COOH$
Hence the anion present in the salt is ‘acetate’ and thus option ‘D’ is the correct option .

Note:
 If we further want to confirm presence of acetate ion in the given salt we can do the Ester Test for which we have to take the given moisturized salt and add drops of sulphuric acid than ethanol, if a fruity smell (due to formation of Ester) is observed we can again confirm presence of acetate ion in the salt