Hess's law and enthalpy cycles Quiz
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5 questions, one answer each
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1. Which expression gives ΔrH from standard enthalpies of formation?
- A. ΣΔfH(products) − ΣΔfH(reactants)
- B. ΣΔfH(reactants) − ΣΔfH(products)
- C. ΣΔfH(products) + ΣΔfH(reactants)
- D. ΣΔfH(reactants) only
2. Which substance has a standard enthalpy of formation of zero?
- A. C(diamond)
- B. H₂O(l)
- C. CO₂(g)
- D. O₂(g)
3. ΔfH of NO(g) = +90.3 kJ mol⁻¹. What is ΔH for N₂(g) + O₂(g) → 2NO(g)?
- A. +90.3 kJ mol⁻¹
- B. +180.6 kJ mol⁻¹
- C. −180.6 kJ mol⁻¹
- D. +45.2 kJ mol⁻¹
4. ΔcH of C(graphite) = −393.5 and ΔcH of CO(g) = −283.0 kJ mol⁻¹. What is ΔfH of CO(g)?
- A. −676.5 kJ mol⁻¹
- B. +110.5 kJ mol⁻¹
- C. −110.5 kJ mol⁻¹
- D. −393.5 kJ mol⁻¹
5. A reaction has ΔH = −92 kJ mol⁻¹. What is ΔH for the reverse reaction?
- A. −92 kJ mol⁻¹
- B. 0 kJ mol⁻¹
- C. −46 kJ mol⁻¹
- D. +92 kJ mol⁻¹