Question

The first and second ionisation enthalpies of a metal are 496 and 4560 kJ $mol^{- 1}$ , respectively. How many moles of HCl and $H_{2}SO_{4}$ , respectively, will be needed to react completely with 1 mole of the metal hydroxide?

• A. 1 and 1
• B. 1 and 2
• C. 2 and 0.5
• D. 1 and 0.5

Answer 1

Answer: (D)

Metal: First ionization enthalpies = 496 kJ/mole
Second ionization enthalpies = 4560 kJ/mol
According to the given information of ionization enthalpies, metal belong to first group i.e. Monovalent cation
$\underset{1 m o l e}{M O H}+\underset{1 m o l e}{H C l} \rightarrow MCl+H_{2}O$
$\underset{1 m o l e}{2 M O H}+\underset{1 / 2 m o l e}{H_{2} S O_{4}} \rightarrow M_{2}SO_{4}+H_{2}O$
That is 1 mole HCl and 0.5 mole $H_{2}SO_{4}$ are needed respectively.