Question

Given below are statements about some molecules/ions. Identify the CORRECT statements.
A. The dipole moment value of $\mathrm{NF_3}$ is higher than that of $\mathrm{NH_3}$.
B. The dipole moment value of $\mathrm{BeH_2}$ is zero.
C. The bond order of $\mathrm{O_2^{2-}}$ and $\mathrm{F_2}$ is same.
D. The formal charge on the central oxygen atom of ozone is $-1$.
E. In $\mathrm{NO_2}$, all the three atoms satisfy the octet rule, hence it is very stable.
Choose the correct answer from the options given below:

• A. A, B, C, D & E
• B. B & C only
• C. B, C & D only
• D. A, C & D only

Hint:

Always check molecular geometry and electron count before deciding dipole moment and octet rule validity.

Answer 1

The Correct Option is C

Let's analyze each statement about the molecules and ions given in the question to determine which of them are correct:

1. Statement A: "The dipole moment value of \(\mathrm{NF_3}\) is higher than that of \(\mathrm{NH_3}\)."

Explanation: Ammonia \((\mathrm{NH_3})\) has a higher dipole moment than nitrogen trifluoride \((\mathrm{NF_3})\). This is due to the orientation of their bond dipoles. In \(\mathrm{NH_3}\), the lone pair of electrons is directed upwards, enhancing the dipole, while in \(\mathrm{NF_3}\), the lone pair is directed against the bond dipoles of the N-F bonds, which reduces the net dipole moment. Hence, this statement is incorrect.

1. Statement B: "The dipole moment value of \(\mathrm{BeH_2}\) is zero."

Explanation: Beryllium hydride \((\mathrm{BeH_2})\) is linear, and the dipole moments of the two Be-H bonds cancel each other out. Therefore, the molecule has a net dipole moment of zero. This statement is correct.

1. Statement C: "The bond order of \(\mathrm{O_2^{2-}}\) and \(\mathrm{F_2}\) is the same."

Explanation: The bond order of \(\mathrm{O_2^{2-}}\) (peroxide ion) is 1, and the bond order of \(\mathrm{F_2}\) is also 1. Therefore, these two molecules have the same bond order. This statement is correct.

1. Statement D: "The formal charge on the central oxygen atom of ozone is -1."

Explanation: In the ozone molecule \((\mathrm{O_3})\), the formal charge calculation shows that the central oxygen atom has a charge of -1. This statement is correct.

1. Statement E: "In \(\mathrm{NO_2}\), all the three atoms satisfy the octet rule, hence it is very stable."

Explanation: The nitrogen dioxide molecule \((\mathrm{NO_2})\) has an odd number of valence electrons (17), so it does not satisfy the octet rule for all atoms. It is actually a free radical, which makes it reactive, not 'very stable'. Hence, this statement is incorrect.

Based on the analysis above, the correct statements are B, C, and D.

Correct Answer: B, C & D only