Let's solve the problem step-by-step to find the percentage of element X and the formula of the violet-colored compound formed when the Lassaigne's extract of the organic compound is treated with sodium nitroprusside.
First, we'll calculate the percentage of the element X in the organic compound based on the mass of barium sulphate
(BaSO4) precipitated.
The molecular weight of barium sulphate,
BaSO4, is:
Molecular weight of
BaSO4=137+32+64=233g∕mol The atomic weight of sulphur (S) is
32g∕mol. When barium sulphate is formed, one mole of
BaSO4 contains one mole of sulphur:
Moles of
BaSO4 formed
= Mass of
BaSO4∕ Molecular weight of
BaSO4 :
Moles of
BaSO4==≈0.00515molMoles of sulphur
= Moles of
BaSO4=0.00515molThe mass of sulphur in the compound is then:
Mass of sulphur
= Moles of sulphur
× Atomic weight of sulphur
=0.00515mol×32g∕mol=0.1648gNow, the percentage of element X (sulphur in this case) in the organic compound is:
So, the percentage of element X is
20.6%.
Next, we need to determine the formula of the violet-colored compound formed when Lassaigne's extract is treated with sodium nitroprusside. The violet coloration is characteristic of the reaction between sodium nitroprusside and sulphur in the extract.
The chemical formula for the violet-colored compound formed in this reaction is:
Na4[Fe(CN)5NOS]Thus, the correct answer is:
Option B
20.6&Na4[Fe(CN)5NOS]