Question

Which of the following halogens combine with dihydrogen at the lowest temperature?

• A. Iodine
• B. Fluorine
• C. Bromine
• D. Chlorine

Hint:

Higher reactivity means lower activation energy for reaction.

Answer 1

The Correct Option is B

Step 1: Recall reactivity of halogens.
Reactivity of halogens decreases down the group: \[ \text{F}>\text{Cl}>\text{Br}>\text{I} \] Step 2: Reaction with hydrogen.
Fluorine reacts explosively with hydrogen even in the dark and at very low temperatures.
Step 3: Conclusion.
Thus, fluorine combines with dihydrogen at the lowest temperature.