JEE Main 2026 Chemistry question
First and second ionization enthalpies of lithium are 520 kJ mol⁻¹ and 7297 kJ mol⁻¹ respectively. Energy required to convert 3.5 mg lithium (g) into Li²⁺(g) [Li(g)→Li²⁺(g)] is (nearest integer) [Molar mass of Li=7 g mol⁻¹]
Answer: 3909
Solution
Energy per mole=520+7297=7817 kJ. Amount of Li=3.5×10⁻³/7=5×10⁻⁴ mol, so energy=7817×5×10⁻⁴=3.9085 kJ≈3909 J.
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