In $Kjeldahl’s$ method,$CuSO_4$ acts as

Given below are two statements :
Statement $I :$ In Lassaigne's test,the covalent organic molecules are transformed into ionic compounds.
Statement $II :$ The sodium fusion extract of an organic compound having $N$ and $S$ gives prussian blue colour with $FeSO_4$ and $FeCl_3$.
In the light of the above statements,choose the correct answer from the options given below.

Given below are two statements :
Statement $I$ : Nitrogen,sulphur,halogen and phosphorus present in an organic compound are detected by Lassaigne's Test.
Statement $II$ : The elements present in the compound are converted from covalent form into ionic form by fusing the compound with Magnesium in Lassaigne's test.
In the light of the above statements,choose the correct answer from the options given below :

Match the List-$I$ with List-$II$:

List-$I$ (Reagent)	List-$II$ (Functional Group detected)
$A$. Sodium bicarbonate solution	$I$. Double bond/unsaturation
$B$. Neutral ferric chloride	$II$. Carboxylic acid
$C$. Ceric ammonium nitrate	$III$. Phenolic $-OH$
$D$. Alkaline $KMnO_4$	$IV$. Alcoholic $-OH$

Choose the correct answer from the options given below:

Nitrogen can be estimated by Kjeldahl's method for which of the following compounds?

Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?