Key Concept: A more reactive halogen displaces a less reactive halogen from its halide solution.
Section A: Reactivity and Predictions
1. Define a displacement reaction in terms of halogens. [1]
2. Put chlorine, bromine and iodine in order of decreasing reactivity. [1]
3. Predict the products (if any) for the reactions below. [3]
a) Chlorine + potassium bromide solution
b) Bromine + potassium iodide solution
c) Iodine + potassium chloride solution
4. Describe the color changes you would see for parts a and b. [3]
Section B: Ionic Equations
5. Write the ionic equation for chlorine displacing bromide ions. [2]
6. Explain why iodine does not displace bromide ions. [2]
Total marks: 12
Mark Scheme
1. A more reactive halogen replaces a less reactive halogen in its compound/solution [1]
2. Cl2 > Br2 > I2 [1]
3. a) KCl + Br2; b) KBr + I2; c) no reaction [3]
4. a) orange/brown from Br2 appears; b) brown solution/iodine forms (dark brown) [3]
5. Cl2 + 2Br- -> 2Cl- + Br2 [2]
6. Iodine is less reactive; cannot oxidize bromide to bromine [2]