Displacement reactions involving the halogens
2 marks · HardPotassium bromide solution is added to separate solutions of chlorine and iodine. Describe what you would observe in each case, and explain why these observations are different.
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
Also accept: Chlorine: solution turns orange as bromine is produced; iodine: no change as iodine is less reactive than bromine.
Common mistakes: Iodine gives colour change with potassium bromide (incorrect); wrong colour for displaced bromine.
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States that an orange colour appears or bromine is produced with chlorine.
B2 · 1 mark · Explains that no reaction (no colour change) occurs with iodine because iodine is less reactive than bromine.
Worked solution
Chlorine: An orange colour appears because chlorine displaces bromine from potassium bromide, forming bromine.
Iodine: There is no observable change because iodine is less reactive than bromine and cannot displace it from potassium bromide.