Question

The following reaction happens in which test:
$N{a_2}S + N{a_2}[Fe{(CN)_5}NO] \to N{a_4}[Fe{(CN)_5}NOS]$
(A) Sodium sulfide test
(B) Sodium nitroprusside test
(C) Both (A) and (B)
(D) None of the above

Answer 1

In order to solve these types of questions we need to know the named reactions and the process by which it is made or in simple words we can say that the how it is prepared so we will do it by the help of lassaigne extract. The appearance of purple coloration confirms the sulfur.

Complete step-by-step answer: For solving this question we need the help of lassaigne test so we will study it first:Lassaigne test: When a small piece of sodium metal is heated gently in a fusion tube upto it to a shining globule then after it the small amount of substance is added and then the tube is heated strongly.We will heat it up to when it turns to red hot after it is plunged into distilled water which should be in china dish. Now the contents are boiled for some time, being cooled and then filtered. The remaining filtrate is known as sodium extract. Since this test was done by lassaigne so it is also called lassaigne extract. The extract contains the content which is sodium sulfide formed by the reaction between sulfur and sodium.According to reaction:$2Na + S \to N{a_2}S$
The lassaigne extract is divided into two parts and now the following test will be performed:
Now the first one is lead acetate test: One part of extract is acidified with acetic acid and then the lead acetate solution is added. Formation of black precipitate confirms the presence of sulfur in the organic compound.According to the equation:
$N{a_2}S + Pb{(C{H_3}COO)_2} \to PbS \downarrow + 2C{H_3}COONa$
Now we will be checking for second one which is sodium nitroprusside test:A few drops of sodium nitroprusside solution are added to another part of the lassaigne extract. The appearance of purple coloration confirms the presence of sulfur.According to the equation:$N{a_2}S + N{a_2}[Fe{(CN)_5}NO] \to N{a_4}[Fe{(CN)_5}NO.S]$
Since we have complete study of sodium nitroprusside solution and the above equation in that, the correct option is sodium nitroprusside test.

Hence (B) option is correct.

Note: We can see that this is mainly the test of presence of sulfur in it.
While we should know that the sodium sulphide test is the localized test for chemicals to detect any concentration of lead in a coating test by the application of sodium sulfide to the coating surface.