EasyChemistryHigh School (11–12)The p-Block Elements › Groups 17 and 18: Halogens and Noble GasesNumericalConceptualA-LevelIB
A student tests four mixtures. In each, one halogen is added to a solution that has the halide of…
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A student tests four mixtures. In each, one halogen is added to a solution that has the halide of another halogen. Use for F2 V, Cl2 V, Br2 V and I2 V. Find the cell potential for chlorine with a bromide solution, bromine with an iodide solution, iodine with a chloride solution, and fluorine with a chloride solution. Say which of the four reactions goes.
Need a reminder? The key ideaShow
A halogen oxidises the halide ion of another halogen when the cell potential is positive. The standard electrode potentials are F2 V, Cl2 V, Br2 V and I2 V. Work in moles: grams divided by molar mass, then use the ratios of the equation. At 273 K and 1 atm, 1 mol of gas fills 22.4 L.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Subtract the two potentials. The sign decides.
Step 1. Chlorine with bromide. . The reaction goes, and bromine forms.
Step 2. Bromine with iodide. . It goes, and iodine forms.
Step 3. Iodine with chloride. . It does not go.
Step 4. Fluorine with chloride. . It goes in principle. In water, fluorine reacts with the water first.
Answer: , , and . Three of the four go.
Check. A halogen only oxidises the halides of the halogens below it in the group.
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