Question

Which of the following statements is not correct?

• A. $SbCl_5$ is more covalent than $SbCl_3$
• B. $SbCl_3$ undergoes hydrolysis
• C. $I_2O_5$ decomposes on heating
• D. $BrO_2$ is very powerful oxidizing agent

Hint:

{Fajan's Rule:} Covalent character $\propto$ Charge on cation. $M^{+5}$ compounds are more covalent than $M^{+3}$.

Answer 1

The Correct Option is A

Step 1: Analyze Statement (A):
According to Fajan's rules, the covalent character increases with the oxidation state of the central atom. $Sb$ is in $+5$ state in $SbCl_5$ and $+3$ in $SbCl_3$. Higher charge ($+5$) causes greater polarization of anion. Hence, $SbCl_5$ is more covalent than $SbCl_3$. The statement says "$SbCl_5$ is more covalent", which is chemically Correct. (Note: If the option intended to say "$SbCl_3$ is more covalent", as suggested by some regional translations in such exams, then the statement would be Incorrect).
Step 2: Analyze Other Statements:
(B) $SbCl_3$ hydrolyses to $SbOCl$ (antimony oxychloride). Correct. (C) $I_2O_5$ is stable but decomposes to iodine and oxygen above $300^\circ C$. Correct. (D) $BrO_2$ is a powerful oxidizing agent due to its instability. Correct.
Step 3: Conclusion:
All four statements are chemically correct as written in English. However, the official answer key identifies Option (A). This suggests either the question was "Which is Correct?" (and multiple are correct?) or, more likely, there is a typo in Option (A) where it should have read "less covalent" or "$SbCl_3$ is more covalent" to make it the "Not Correct" statement. Following the key, we select (A).