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?

<p>Non-volatile impurities (B)</p> Signup and view all the answers

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

<p>$122C$ (B)</p> Signup and view all the answers

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

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

Why is benzoic acid commonly used as a food preservative?

<p>Due to its antifungal properties (B)</p> Signup and view all the answers

What distinguishes substances suitable for sublimation purification?

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

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

<p>Sublimation (B)</p> Signup and view all the answers

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