The student leaves one end of a wooden splint in $R$ for ten minutes, then places the damp end of the wooden splint into the flame of a Bunsen burner with the air hole open. The student decides that $R$ contains sodium ions. State the observation that supports this decision.
Explain why the air hole on the Bunsen burner has to be open for this flame test.
The student adds dilute nitric acid to $R$ and sees a colourless gas fizzing out, which turns limewater milky. State the conclusions drawn from these observations.
The student adds aqueous barium nitrate to some of the mixture from (b)(i). The student concludes that $R$ contains sulfate ions. State the observation that leads to this conclusion.
The student adds aqueous silver nitrate to some of the mixture from (b)(i). The student sees a colourless solution. State a conclusion from this observation.
The student adds aqueous sodium hydroxide to $R$ and heats the mixture. Describe a test and observation that show that $R$ does not contain ammonium ions.
Solution $R$ is a mixture of two different ionic compounds. Suggest the names of these two compounds.
The student tests another solution, $P$, and finds it hard to tell whether the solution contains chloride ions or bromide ions. The student also has aqueous potassium chloride and aqueous potassium bromide. Suggest how the student could use the aqueous potassium chloride and aqueous potassium bromide to make it easier to decide whether $P$ contains chloride ions or bromide ions.
The student adds dilute hydrochloric acid to a different solution and a gas is released. The gas is then led through limewater. Describe how the gas can be passed through limewater. You may draw a labelled diagram to help answer the question.