Displacement reactions involving the halogens
3 marks · EasyWhat is observed when bromine water is added to a solution of potassium iodide?
Write the balanced chemical equation for the reaction.
State why this reaction occurs, using the reactivity trend of the halogens.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) The solution turns brown.
(b) 2KI(aq) + Br2(aq) -> 2KBr(aq) + I2(aq)
(c) Bromine is more reactive than iodine so bromine displaces iodine from potassium iodide.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · One mark for brown colour observed.
B2 (b) · 1 mark · One mark for correct balanced equation: 2KI(aq) + Br2(aq) -> 2KBr(aq) + I2(aq)
B3 (c) · 1 mark · One mark for correct explanation of reactivity: bromine is more reactive than iodine.
Worked solution
a) When bromine water is added to potassium iodide solution, iodine is formed and the solution turns brown.
b) This reaction occurs because bromine is more reactive than iodine and can displace iodine from its compound.