Question

Which of the following pairs contain isostructural species? \[ \begin{aligned} \text{I. } & \mathrm{H_3PO_3,\ H_2SO_4} \\ \text{II. } & \mathrm{SO_3,\ BF_3} \\ \text{III. } & \mathrm{O_3,\ NO_2^-} \end{aligned} \] The correct answer is

• A. I, II only
• B. II, III only
• C. I, II, III
• D. I, III only

Hint:

Common isostructural pairs: \[ \boxed{\mathrm{SO_3\ \&\ BF_3}} \] \[ \boxed{\mathrm{O_3\ \&\ NO_2^-}} \] Both members of each pair have identical molecular geometry.

Answer 1

The Correct Option is C

Step 1: Compare the structures. \[ \mathrm{H_3PO_3} \] and \[ \mathrm{H_2SO_4} \] both possess tetrahedral arrangement around the central atom. \[ \boxed{\text{Pair I is isostructural}.} \] \[ \mathrm{SO_3} \] and \[ \mathrm{BF_3} \] are both \[ \boxed{\text{trigonal planar}.} \] Hence, \[ \boxed{\text{Pair II is isostructural}.} \] \[ \mathrm{O_3} \] and \[ \mathrm{NO_2^-} \] both have \[ \boxed{\text{bent (V-shaped) geometry}.} \] Thus, \[ \boxed{\text{Pair III is isostructural}.} \] Therefore, \[ \boxed{\text{I, II and III}} \] Hence, \[ \boxed{(C)} \] is the correct answer.