1
Which reaction is not feasible?
- 2KI + Br2 2KBr + I2
- 2KBr + I2 2KI + Br2
- 2KBr + Cl2 2KCl + Br2
- 2H2O + 2F2 4HF + O2
Answer
(2) 2KBr + I2 2KI + Br2
Solution
As per NCERT, the oxidising power of halogens decreases in the order F2 > Cl2 > Br2 > I2, so a halogen displaces only a halogen lower in the series from its halide.
⇒ Br2 displaces I- and Cl2 displaces Br-: reactions (1) and (3) occur.
⇒ F2 is so reactive that it oxidises water to O2: reaction (4) occurs.
∵ I2 is a weaker oxidising agent than Br2, it cannot oxidise Br- to Br2.
∴ 2KBr + I2 2KI + Br2 is not feasible.
Answer: (2)
AIPMT 2002