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Combined Science — Chemistry Flashcards

6 cards from real O-LEVEL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the relative formula mass of NaCl? (Na=23, Cl=35.5)

    Answer: 58.5

    Mr(NaCl) = 23 + 35.5 = 58.5.

  2. Which type of reaction involves a more reactive element displacing a less reactive one from its compound?

    Answer: Displacement

    In a displacement reaction, a more reactive element displaces a less reactive element from its compound, e.g., zinc displacing copper from copper sulfate solution.

  3. What is the name given to a compound that contains only carbon and hydrogen?

    Answer: Hydrocarbon

    Hydrocarbons are compounds that contain only carbon and hydrogen atoms, e.g., methane (CH₄), ethane (C₂H₆).

  4. In the reactivity series, which metal is most reactive?

    Answer: Potassium

    Potassium (K) is one of the most reactive metals, placed at the top of the reactivity series, reacting vigorously with water.

  5. What is the term for the splitting of a compound using electricity?

    Answer: Electrolysis

    Electrolysis is the decomposition of an ionic compound (electrolyte) using electrical energy. 'Electro' means electricity, 'lysis' means splitting.

  6. How many moles are in 44 g of carbon dioxide (CO₂)? (C=12, O=16)

    Answer: 1

    Mr(CO₂) = 12 + (16×2) = 44. Moles = mass/Mr = 44/44 = 1 mole.

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