Question

Which ion in each of the following pairs would you expect to be more strongly hydrated? Why?(a)Na⁺ or Mg⁺²b) Mg⁺² or Be⁺²c) Fe⁺² or Fe⁺³d) F^- or Br^-e) Cl^- or ClO₄^-f) ClO₄^- or SO₄^2-

Short answer

Higher the charger greater is the hydration energy and the smaller the size greater the hydration energy.

(a) Mg⁺² is more strongly hydrated

(b) Be⁺² is more strongly hydrated

(c) Fe⁺³ is more strongly hydrated

(d) F^- is more strongly hydrated

(e)Cl^- is more strongly hydrated

(f) SO₄^2- is more strongly hydrated

Step-by-step solution

Explanation regarding part (a)

Mg⁺² has a more positive charge and is smaller in size as compared to Na⁺. Hence it has more tendency to attract surrounding water molecules.

Explanation regarding part (b)

Mg⁺² and Be⁺² both have the same positive charge but the size of Be⁺² is smaller so it will get more hydrated.

Explanation regarding part (c)

Fe⁺³ will get more strongly hydrated because of the higher charge as compared to Fe⁺²

Explanation regarding part (d)

Both the ion F^-and Br^-have the same charge on it but F^- is smaller in size so it will get more hydrated.

Explanation regarding part (e)

Cl^- is much smaller in size as compared to ClO₄^- that’s why it will get strongly hydrated.

Explanation regarding part (f)

SO₄^2- has more negative charge on it as compared to ClO₄^- that’s why it will get strongly hydrated.