Consider the following two graphs between atomic number of element and hydration enthalpies (at 25°C — s Block Elements Chemistry Question
Question
Consider the following two graphs between atomic number of element and hydration enthalpies (at 25°C) of corresponding ion. (M = Alkali metal and X = halogens) [SEE DIAGRAM] Then according to the given information which of the following is/are correct relationship between enthalpy of solution ($\Delta$H_solution) of a salt MX in water and difference of the enthalpies of hydration ($\Delta$H_hydration) of the constituent ion (M+ and X-).
💡 Solution & Explanation
Step 1: When highly reactive metals are burned in air, they can react with atmospheric nitrogen to form metal nitrides. Lithium (Li) and alkaline earth metals (Mg, Ca) easily form nitrides (Li3N, Mg3N2, Ca3N2) due to high lattice energy stabilization. Step 2: Potassium (K) has a larger cationic size and lower lattice energy, which prevents it from reacting directly with nitrogen gas to form a stable nitride on burning in air. Step 3: Upon exposure to moisture, the nitrides of Li, Mg, and Ca hydrolyze to release ammonia gas (NH3), which has a characteristic sharp smell. Since Potassium does not form a nitride, it does not produce ammonia under these conditions. Thus, option (c) is correct.