Question

Which of the following oxidises water to oxygen?
A. Chlorine
B. Fluorine
C. Bromine
D. Iodine

Answer 1

Hint: A strong oxidising agent among the halogens can easily oxidise water to oxygen. Among the halogens the as the size of the halogen increases oxidising property decreases.

Complete Step by Step Answer:
The electronic configuration of $F$$ is: $$1s^22s^22p^5$.
$F$ has $5$ electrons in a 2p shell. So, to get stability it needs one more electron and accepts one electron. Thus it acts as an oxidising agent not as a reducing agent. It is more reactive than oxygen.
Thus it can easily oxidise water to oxygen gas and reduce itself. The reaction is given as follows
$2{{F}_{2}}+2{{H}_{2}}O\to 4HF+{{O}_{2}}$
Thus in this reaction fluorine gas reacts with two moles of water and oxidises water to oxygen gas and reduces itself to hydrogen fluoride. Thus oxygen gas and hydrogen fluoride are formed as products.
Chlorine, bromine and iodine are less reactive than oxygen so, they can’t oxidise water to oxygen gas.
Thus we can write that fluorine oxidises water to oxygen gas.
Thus the correct option is B.

Note: A strong oxidising agent means it helps to oxidise other substances and itself get reduced. Due to small size and high electronegativity fluorine attracts the electron and does not remove it easily.