The method and the results are on the periodic table groups lab. Do the analysis yourself first, then check the answers below.
Quick answer: Group 1 metals have one outer electron and become more reactive down the group, reacting with water to make hydrogen and an alkaline hydroxide. These answers go with the Chemistry 9-10 lab on periodic table groups: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Here are the periodic table groups lab answers for chemistry grades 9-10: graph, calculations, uncertainties and conclusion. First do the lab yourself, then compare, and go back to the lesson if needed.
These model answers use the sample results. They show how a pattern of reactions leads to an order of reactivity, and how the trend can be explained using electron shells.
Level: Chemistry grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE C1, IGCSE 9
Periodic table groups lab answers: the analysis explained
Question 1 Which reactions occurred
Chlorine reacted with potassium bromide and potassium iodide. Bromine reacted with potassium iodide only. Iodine reacted with none.Three reactions in total: Cl + KBr, Cl + KI, Br + KI.
Question 2 Write the equations
Cl₂ + 2KBr → 2KCl + Br₂Cl₂ + 2KI → 2KCl + I₂
Br₂ + 2KI → 2KBr + I₂
Each equation shows a more reactive halogen displacing a less reactive one.
Question 3 Order of reactivity
Chlorine displaced both other halogens, bromine displaced only iodine, and iodine displaced neither.Order: chlorine, bromine, iodine.
Question 4 Explain with electrons
Chlorine (2,8,7) has three shells and iodine has five. In chlorine the electron it gains goes into a shell closer to the nucleus with less shielding, so the attraction is stronger.Fewer shells means stronger attraction, so chlorine is more reactive.
Question 5 Why use a control
Iodine solution is brown already, and a brown product would look similar. The control shows the starting colour so that real changes can be compared.The control provides the starting colour for comparison.
Question 6 Make the tests fairer
Use the same volume and concentration in every tube, a white background and repeats of each mixture. A hexane layer (used by the teacher) could extract the halogen and show its colour more clearly.Fixed volumes, repeats and a white background.
Question 7 Predict for astatine
Astatine is below iodine in Group 7, so it is less reactive. A more reactive halogen displaces a less reactive one, so iodine would displace astatine.Yes: iodine is more reactive than astatine.
