Question

Extent of hydration of $Na ^{+}, Mg ^{2+}, Al ^{3+}$ is in order

• A. $Na^+ < Al^{3+} < Mg^{2+}$
• B. $Na^+ < Mg^{2+} < Al^{3+}$
• C. $Al^{3+} < Mg^{2+} < Na^+$
• D. Equal

Answer 1

Answer: (B)

$Na ^{+}, Mg ^{2+}$ and $Al ^{3+}$ are isoelectronic
Size $Na ^{+}> Mg ^{2+}> Al ^{3+}$
Charge $+1+2+3$
Smaller the size of cation,
Larger the charge,
Greater the hydration
Thus, $Na ^{+}< Mg ^{2+}< Al ^{3+}$