For which of the following reaction \Delta H^\circ value is equal to the first ionization energy of — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Recall the definition of the first ionization energy: the energy required to remove one electron from an isolated, neutral gaseous atom in its ground state. Step 2: The chemical equation must represent one mole of neutral Calcium in the gaseous state, Ca(g), losing one electron to form one mole of Ca^+(g) ions. Step 3: This process is represented by the equation in option (b): Ca(g) -> Ca^+(g) + e^-.