Identify the incorrect statement from the following:
- The acidic strength of HX (X = F, Cl, Br and I) follows the order: HF > HCl > HBr > HI.
- Fluorine exhibits –1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also.
- The enthalpy of dissociation of F2 is smaller than that of Cl2.
- Fluorine is stronger oxidising agent than chlorine.
The Correct Option is A
Solution and Explanation
To identify the incorrect statement related to the chemical properties of halogen acids (HX), let's analyze each option:
-
Statement: The acidic strength of HX (X = F, Cl, Br, and I) follows the order: HF > HCl > HBr > HI.
Explanation: The acidic strength of hydrogen halides in aqueous solution is determined by the bond strength between hydrogen and the halide. As we move down the group from fluorine (F) to iodine (I), the bond strength decreases because the bond length increases. Consequently, HF is the weakest acid while HI is the strongest. Hence, the correct order of acidic strength is HI > HBr > HCl > HF. Therefore, this statement is incorrect.
-
Statement: Fluorine exhibits -1 oxidation state whereas other halogens exhibit +1, +3, +5, and +7 oxidation states also.
Explanation: Fluorine, being the most electronegative element, only exhibits a -1 oxidation state. Other halogens like Cl, Br, and I can exhibit positive oxidation states such as +1, +3, +5, and +7 due to their ability to expand their octet using d-orbitals. Thus, this statement is correct.
-
Statement: The enthalpy of dissociation of F2 is smaller than that of Cl2.
Explanation: The F-F bond in F2 is relatively weak due to strong repulsion between the lone pairs on the small fluorine atoms. As a result, the bond dissociation enthalpy of F2 is indeed lower than that of Cl2. Therefore, this statement is correct.
-
Statement: Fluorine is a stronger oxidizing agent than chlorine.
Explanation: Fluorine is the most electronegative element and has a high tendency to gain electrons, making it a very strong oxidizing agent, even stronger than chlorine. This statement is correct.
Conclusion: The incorrect statement is: "The acidic strength of HX (X = F, Cl, Br, and I) follows the order: HF > HCl > HBr > HI."
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