Elements, Compounds & Mixtures Quiz
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5 questions, one answer each
Each answer is checked as you go, with why.
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1. Which of these is a mixture rather than a compound?
- A. Water
- B. Carbon dioxide
- C. Air
- D. Sodium chloride
2. Which technique would best separate salt dissolved in water, recovering the salt as crystals?
- A. Filtration
- B. Crystallisation
- C. Chromatography
- D. Simple distillation
3. A student measures the melting point of a white solid and finds it melts sharply at exactly 158°C. This suggests the solid is:
- A. A mixture
- B. Pure
- C. A gas
- D. Insoluble
4. In a chromatogram, a dye spot travels 7.2 cm while the solvent front travels 8 cm. What is its Rf value?
- A. 0.72
- B. 0.8
- C. 0.9
- D. 1.11
5. A mixture of ethanol and water (different boiling points, fully miscible) needs to be separated into its pure components. Which method is most appropriate and why?
- A. Filtration, because one is a solid
- B. Fractional distillation, because the liquids have different boiling points and are miscible
- C. Crystallisation, because ethanol will crystallise out
- D. Chromatography, because it separates liquids by colour