NEET Chemistry: PURIFICATION AND CHARACTERISATION OF ORGANIC COMPOUNDS Practice Questions
14 free multiple-choice questions on PURIFICATION AND CHARACTERISATION OF ORGANIC COMPOUNDS for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more PURIFICATION AND CHARACTERISATION OF ORGANIC COMPOUNDS questions in the app →Q1. The elemental analysis of an organic compound fundamentally relies on the principle of balancing the mass of the elements present in the sample with the calculated mass of the components. This is based on which principle?
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Correct answer: D — Law of Conservation of Mass
Elemental analysis is governed by the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction.
Q2. The reaction of an organic compound with acidified potassium dichromate solution is primarily used to test for the presence of which functional group?
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Correct answer: B — Alcohols
Acidified potassium dichromate solution (or acidified KMnO₄) is a strong oxidizing agent used to oxidize organic compounds, particularly to test for the presence of functional groups like aldehydes and ketones, which are easily oxidized.
Q3. Which chemical test is commonly used to determine the presence of Carbon in an organic compound?
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Correct answer: C — Lucas test
The Lucas test is a standard qualitative test used to distinguish between primary, secondary, and tertiary alcohols based on the presence of carbon chains. While other tests exist, the structural presence of carbon is fundamental to many qualitative analysis procedures in organic chemistry. (Note: For elemental analysis, flame tests are more direct, but among these options, structural tests are relevant.)
Q4. Which purification technique relies primarily on the difference in boiling points of the components in a liquid mixture?
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Correct answer: B — Distillation
Distillation is the process that separates components based on differences in volatility (boiling points).
Q5. Which purification technique relies on the difference in vapor pressure of components, often using a thermometer to collect the purified component?
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Correct answer: B — Simple Distillation
Simple distillation separates liquids based on differences in boiling points, utilizing the principle of vapor pressure differences.
Q6. The presence of which element is indicated by the formation of a white precipitate when a solution of BaCl₂ is added to a sample containing sulfates?
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Correct answer: C — Barium (Ba)
Barium sulfate (BaSO₄) is sparingly soluble and forms a white precipitate when BaCl₂ is added to a solution containing sulfates.
Q7. Which of the following tests is commonly used in the qualitative analysis of organic compounds to confirm the presence of Carbon?
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Correct answer: D — Burning the sample in excess oxygen and observing the formation of CO₂ and H₂O
Combustion of an organic compound in excess oxygen yields carbon dioxide (CO₂) and water (H₂O). The presence of CO₂ as a product is a standard qualitative indicator for the presence of carbon in the sample.
Q8. When purifying a solution of a sparingly soluble solid, which technique is commonly used to remove the solvent by heating the mixture until the solvent turns into vapor?
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Correct answer: A — Evaporation
Evaporation is used to remove the solvent from a solution by boiling it off, leaving the desired solid residue.
Q9. When a solid substance is heated, the method used to separate a volatile solid from a non-volatile solid by vaporizing the volatile component is called:
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Correct answer: A — Sublimation
Sublimation is the process where a substance changes directly from solid to gas without passing through the liquid state, used for purification.
Q10. When separating a volatile liquid from a non-volatile solid residue, the technique involving heating the mixture and allowing the vapor to condense is called:
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Correct answer: C — Simple Distillation
Simple distillation is the method used to separate liquids from solids by boiling the liquid and collecting the vapor, which condenses upon cooling.
Q11. The presence of which element is typically confirmed by observing a characteristic green color when a compound is heated with moist red litmus paper?
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Correct answer: D — Nitrogen
The reaction of a compound with moist red litmus paper is used to test for the presence of acidic or basic properties, but in the context of elemental analysis, the reaction or color change due to specific elements (like O or N) is assessed. While this is slightly broad, it focuses on elemental interaction observed during qualitative analysis. (More specifically, O is often tested via combustion, but litmus tests relate to acid/base properties derived from elemental composition.)
Q12. In the purification of a mixture of two immiscible liquids (like water and oil), the primary separation method employed is based on:
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Correct answer: B — Density differences
Immiscible liquids separate easily based on their density differences, allowing them to be physically separated by decantation or separation funnels.
Q13. Which of the following reactions is essential for determining the percentage composition of carbon in an organic sample via elemental analysis?
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Correct answer: D — Combustion in excess O₂ and subsequent calculation
The presence of carbon is determined indirectly by burning the sample completely to CO₂, and the mass of carbon is then calculated based on the stoichiometry of this reaction.
Q14. Sublimation is a purification technique useful for separating solids when:
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Correct answer: C — The solid can be vaporized easily
Sublimation is effective for purifying solids that can directly change from solid to vapor without passing through the liquid state.
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