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Chemistry · May / June 2020 · Paper 42 · Question 4

0620

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The question as text

Oxygen is produced by the decomposition of hydrogen peroxide. Manganese(IV) oxide is the catalyst for this reaction.

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  • 4(a)[2]

    substance that speeds up a reaction / increases rate (1)

    unchanged (chemically) at the end OR not used up OR lowers activation energy OR provides alternative pathway (1)

  • 4(b)[4]

    rate decreases (1)

    particles further apart / less particles per unit volume (1)

    fewer collisions per unit time / lower collision frequency (1)

    reaction stops because all hydrogen peroxide is used up

  • 4(c)[2]

    steeper gradient (1)

    reaches same volume of oxygen (1)

  • 4(d)[3]

    particles gain kinetic energy / particles move faster (1)

    greater number of collisions with activation energy (or more) / greater number of particles with activation energy (or more) / greater number of particles with energy required for reaction (1)

    more collisions are successful / more collisions are fruitful / more collisions lead to reaction (1)

  • 4(e)[3]

    48.0

    M1 moles of oxygen

    or moles of oxygen = 0.002 (1)

    24000

    M2 moles of hydrogen peroxide = M1 × 2 or moles of hydrogen peroxide = 0.004 (1)

    M3 concentration = M2 × 40 = 0.16 mol / dm3 (1)

    allow ECF

  • 4(f)[2]

    2KClO3 → 2KCl + 3O2

    ALL formulae correct (1)

    balancing (1)

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