Q3 / 160 · TS EAMCET 2018 (05 May Shift 1) · Chemistry

The correct option for the first ionisation enthalpy (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) of $\mathrm{Li}, \mathrm{Na}, \mathrm{K}$ and $\mathrm{Cs}$ respectively is

  • A
    $496,520,419,374$
  • B
    $374,419,496,520$
  • Correct answer
    C
    $520,496,419,374$
  • D
    $374,419,520,496$

Solution

First ionisation enthalpy increase with smaller size. Li is smallest. So, Li has highest first ionisation enthalpy. $$ \mathrm{Li}>\mathrm{Na}>\mathrm{K}>\mathrm{Cs} \text {. } $$

Hence, the correct answer is option: 'C'.

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