JEE MAIN - Chemistry (2020 - 9th January Evening Slot - No. 3)
The first and second ionisation enthalpies of a
metal are 496 and 4560 kJ mol–1, respectively.
How many moles of HCl and H2SO4,
respectively, will be needed to react completely
with 1 mole of the metal hydroxide ?
1 and 2
1 and 0.5
1 and 1
2 and 0.5
Explanation
First ionization enthalpies = 496 kJ/mole
Second ionization enthalpies = 4560 kJ/mol
According to the given information, the difference between first and second ionization enthalpy is very high so Metal belong to 1st group i.e. Monovalent cation.
Metal hydroxide will be of type, MOH.
MOH + HCl $$ \to $$ MCl + H2O
MOH + $${1 \over 2}$$H2SO4 $$ \to $$ $${1 \over 2}$$M2SO4 + H2O
So one mole of HCl required to react with one mole MOH.
And $${1 \over 2}$$ mole of H2SO4 required to react with one mole MOH.
Second ionization enthalpies = 4560 kJ/mol
According to the given information, the difference between first and second ionization enthalpy is very high so Metal belong to 1st group i.e. Monovalent cation.
Metal hydroxide will be of type, MOH.
MOH + HCl $$ \to $$ MCl + H2O
MOH + $${1 \over 2}$$H2SO4 $$ \to $$ $${1 \over 2}$$M2SO4 + H2O
So one mole of HCl required to react with one mole MOH.
And $${1 \over 2}$$ mole of H2SO4 required to react with one mole MOH.
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