Question:
The first and second ionisation enthalpies of a metal are 496 and $4560 \mathrm{~kJ} \mathrm{~mol}^{-1}$, respectively. How many moles of $\mathrm{HCl}$ and $\mathrm{H}_{2} \mathrm{SO}_{4}$, respectively, will be needed to react completely with 1 mole of the metal hydroxide?
Correct Option: , 4
Solution:
A large difference between first and second ionisation enthalpies $\left(4560-496=4064 \mathrm{~kJ} \mathrm{~mol}^{-1}\right)$ confirms the metal to be an alkali metal and thus is monovalent and form hydroxide of the type $\mathrm{M}(\mathrm{OH})$.
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