Lassaigne S Test

We are given the following information: - Mass of organic compound = 0.8 g - Mass of barium sulphate precipitated = 1.2 g - The chemical reaction involving HNO₃ and the barium chloride shows that the element X is in the form of sulphate. 1. Molar Mass of Barium Sulphate The molar mass of barium sulphate (BaSO₄) is calculated as: 2. Moles of Barium Sulphate The moles of barium sulphate precipitated is given by: 3. Moles of Element X In the reaction, one mole of element X reacts to form one mole of barium sulphate. Hence, moles of X in the compound is equal to the moles of BaSO₄ formed: 4. Mass of Element X The mass of element X is: From the stoichiometry and element identification, we deduce that X is sulfur, which has an atomic mass of 32 g/mol. Thus: 5. Percentage of Element X The percentage of element X in the compound is: 6. Formula of Violet-Coloured Compound The violet-coloured compound formed when Lassaigne's extract reacts with sodium nitroprusside is , which corresponds to the formula in option (B). Thus, the percentage of element X is 20.6% and the formula of the violet-coloured compound is Na₄[Fe(CN)₆NOS], corresponding to option (B).