Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

When sodium reacts with oxygen, heat energy is released and the compound $\text{Na}_2\text{O}$ is formed. The reaction equation is shown here: $2\text{Na}(\text{s}) + \tfrac{1}{2}\text{O}_2(\text{g}) \rightarrow \text{Na}_2\text{O}(\text{s})$. Which statement about this reaction is correct?

  • A$\Delta H^\circ$ for the reaction is equal to twice the bond energy of the Na-O bond.
  • B$\Delta H^\circ$ for the reaction is positive.
  • CThe equation represents the standard enthalpy change of combustion of sodium.
  • DThe equation represents the standard enthalpy change of formation of sodium oxide.

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