1. Tardigrade
  2. Question
  3. Chemistry
  4. The ionization enthalpies of Li and Na are 520 kJ mol-1 and 495 kJ mol-1 respectively. The energy required to convert all the atoms present in 7 mg of Li vapours and 23 mg of sodium vapours of their respective gaseous cations respectively are

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Q. The ionization enthalpies of $Li$ and Na are $520 \,kJ\, mol^{-1}$ and $495\, kJ\, mol^{-1}$ respectively. The energy required to convert all the atoms present in $7\, mg$ of $Li$ vapours and $23\, mg$ of sodium vapours of their respective gaseous cations respectively are

Classification of Elements and Periodicity in Properties

Solution:

No. of moles of $Li = \frac{7}{1000 \times 7} = 10^{-3}$
No. of moles of $Na = \frac{23}{1000 \times 23} = 10^{-3}$
$\therefore \quad$ The amount of energies required for $10^{-3}$ mole each of $Li$ and $Na$ are $520 \,kJ \times 10^{-3}$ and $495 \,kJ \times 10^{-3}$ or $520\, J$ and $495\, J$ respectively.