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Chemical Analysis: Qualitative and Quantitative Analysis

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Chemical Analysis: Qualitative and Quantitative Analysis

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Questions and Answers

What is the role of sodium carbonate in the extraction of caffeine?

React with tannin and gallic acid to form products soluble in dichloromethane (correct)

React with benzoic acid to form a solid precipitate

React with caffeine to facilitate extraction

React with water to remove impurities

What is the purpose of anhydrous sodium sulfate in the extraction process?

Remove water from the organic layer (correct)

React with caffeine to form a soluble compound

React with impurities to make them volatile

Enhance the solubility of benzoic acid

What is sublimation as described in the text?

Transition of a solid into a gas without passing through the liquid stage (correct)

Transition of a gas into a solid

Transition of a liquid into a gas

Transition of a solid into a liquid

Which type of impurity makes substances suitable for purification by sublimation?

Non-volatile impurities (B) Signup and view all the answers

At what temperature does benzoic acid change from a solid to a liquid?

$122C$ (B) Signup and view all the answers

What distinguishes pure substances from impure substances in terms of melting points?

Impure substances melt over a wide range of temperatures (B) Signup and view all the answers

Why is benzoic acid commonly used as a food preservative?

Due to its antifungal properties (B) Signup and view all the answers

What distinguishes substances suitable for sublimation purification?

Non-volatile impurities or lower vapor pressure than pure compounds (C) Signup and view all the answers

Which process involves the conversion of a solid directly into a gas?

Sublimation (B) Signup and view all the answers