Question

The ease of adsorption of the hydrated alkali metal ions on an ion exchange resins follows the order?

• A.
  $\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$
• B.
  ${\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{R}{\mathrm{b}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$
• C.
  $\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}<{\mathrm{K}}^{+}<\mathrm{R}{\mathrm{b}}^{+}$
• D.
  $\mathrm{L}{\mathrm{i}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{R}{\mathrm{b}}^{+}$

Answer 1

The correct option is A

$\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$

The explanation for the correct option:

Option(A): $\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$

• The ease of adsorption of the hydrated alkali metal ions on an ion exchange resin decreases with the increase in the size of the alkali metal ion.
• Here the order of the size of alkali metal ion can be given as:

$\mathrm{L}{\mathrm{i}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<{\mathrm{K}}^{+}<\mathrm{R}{\mathrm{b}}^{+}$

• Thus, the ease of adsorption of the hydrated alkali metal ions can be given in the order:

$\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$

The explanation for the incorrect option:

Option(B): ${\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{R}{\mathrm{b}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$

• Here the order of the ease of adsorption of the hydrated alkali metal ions has been given in the wrong order as per the above-mentioned concept.
• Hence, the given option is the incorrect one.

Option(C): $\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}<{\mathrm{K}}^{+}<{\mathrm{Rb}}^{+}$

• The ease of adsorption of the hydrated alkali metal ions can be given in the order: $\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$, which is given in the reverse order of the size of the alkali metal ion.
• Hence, the given option does not coincide with the correct concept.

Option(D): $\mathrm{L}{\mathrm{i}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<{\mathrm{Rb}}^{+}$

• The order of the size of alkali metal ion can be given as: $\mathrm{L}{\mathrm{i}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<{\mathrm{K}}^{+}<\mathrm{R}{\mathrm{b}}^{+}$, which is given in the reverse order of the ease of adsorption of the hydrated alkali metal ions.
• Hence, the given concept does not represent the correct concept.

Hence, the ease of adsorption of the hydrated alkali metal ions on an ion exchange resins follows the order:
$\mathrm{R}{\mathrm{b}}^{+}<{\mathrm{K}}^{+}<\mathrm{N}{\mathrm{a}}^{+}<\mathrm{L}{\mathrm{i}}^{+}$, option (A) is the correct answer.