NEET Practice Questions (MCQs) with Answers & Solutions

In the estimation of sulfur in an organic compound, the sulfur is typically converted to sulfate ion (SO₄²⁻), which is then precipitated as barium sulfate (BaSO₄). The amount of sulfur is determined by measuring the mass of BaSO₄ formed. So, the correct answer is BaSO₄.

In the estimation of phosphorus in organic compounds, the phosphorus is precipitated as magnesium ammonium phosphate. Upon ignition, it is converted to magnesium pyrophosphate (Mg2P2O7), which is weighed to determine the amount of phosphorus. This method ensures accurate quantification of phosphorus content.

Sublimation is the best method to purify camphor from common salt. Camphor sublimes, i.e., it transitions directly from solid to vapor without passing through a liquid phase, while common salt does not. This property allows camphor to be separated effectively from the non-sublimable impurities like common salt.

Fractional distillation is used to separate a mixture of methanol and acetone. Both substances have different boiling points (methanol boils at 64.7°C and acetone at 56.0°C). Fractional distillation allows for the separation of components in a mixture based on differences in boiling points, making it suitable for separating methanol and acetone.

Sublimation is the method used to purify naphthalene because naphthalene sublimes, which means it can transition directly from a solid to a gas without passing through a liquid state. This property allows for its purification by heating the impure sample so that the naphthalene vaporizes and then condenses back into a solid upon cooling.

Distillation is the method used to separate a mixture of acetone and ethanol because they have different boiling points. Acetone boils at around 56°C, whereas ethanol boils at around 78°C. By heating the mixture, acetone will vaporize first, allowing it to be condensed and collected separately from ethanol.

Sublimation is the suitable technique for separating a mixture of calcium sulphate and camphor because camphor can sublimate (change directly from solid to gas) upon heating, while calcium sulphate does not. This property allows camphor to be separated from calcium sulphate effectively.

Steam distillation is the appropriate method for extracting essential oils from flowers. Essential oils are steam volatile and can be distilled along with water vapor, which allows them to be separated from the non-volatile organic compounds present in the flowers.