Hess's law and enthalpy cycles

Hess's law and enthalpy cycles Quiz

Edexcel A-Level Chemistry: Quiz

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5 questions, one answer each

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  1. 1. Which of these is the correct expression for ΔrH using standard enthalpy changes of combustion?

    • A. Σ ΔcH(products) − Σ ΔcH(reactants)
    • B. Σ ΔcH(reactants) − Σ ΔcH(products)
    • C. Σ ΔcH(reactants) + Σ ΔcH(products)
    • D. Σ ΔcH(reactants) × Σ ΔcH(products)

  2. 2. Which has a standard enthalpy change of formation of zero?

    • A. CO₂(g)
    • B. H₂O(l)
    • C. O₂(g)
    • D. CH₄(g)

  3. 3. The enthalpy change of reaction A → B is −50 kJ mol⁻¹ and B → C is −30 kJ mol⁻¹. What is ΔH for C → A?

    • A. −80 kJ mol⁻¹
    • B. −20 kJ mol⁻¹
    • C. +20 kJ mol⁻¹
    • D. +80 kJ mol⁻¹

  4. 4. 0.0200 mol of a solid dissolves in 50.0 cm³ of water and the temperature falls by 4.0 K. Using c = 4.18 J g⁻¹ K⁻¹, what is ΔH?

    • A. −41.8 kJ mol⁻¹
    • B. +41.8 kJ mol⁻¹
    • C. +0.836 kJ mol⁻¹
    • D. −0.836 kJ mol⁻¹

  5. 5. Using ΔfH values CO(g) −111 and CO₂(g) −394 kJ mol⁻¹, what is ΔH for CO(g) + ½O₂(g) → CO₂(g)?

    • A. −505 kJ mol⁻¹
    • B. +283 kJ mol⁻¹
    • C. −283 kJ mol⁻¹
    • D. +505 kJ mol⁻¹

Quiz