The student leaves one end of a wooden splint dipped in R for ten minutes. The damp end of the splint is then put into a blue Bunsen burner flame.\n\nThe flame first shows a red colour briefly and then becomes yellow.\n\nState two possible conclusions from this observation.
Explain why the observation in (a)(i) does not allow a definite conclusion.
The student first adds dilute nitric acid to R, then adds aqueous barium nitrate.\n\nThe student decides that R does not contain sulfate ions.\n\nState the observation that lets the student reach this conclusion.
The student adds dilute nitric acid to R, then adds aqueous silver nitrate.\n\nA white precipitate is seen.\n\nState a conclusion from this observation.
The student adds aqueous silver nitrate to aqueous sodium carbonate, and a white precipitate appears.\n\nThe student then adds dilute nitric acid drop by drop until there is no further change.\n\nThe white precipitate dissolves and a colourless solution is produced.\n\nDescribe one other observation.
Suggest why dilute nitric acid is added in (c).
The student adds a few drops of aqueous sodium hydroxide to R.\n\nState the observation that suggests R may contain $\text{Ca}^{2+}$.
Describe what else the student must do to confirm the presence of $\text{Ca}^{2+}$ ions.\n\nState what the student sees.
The student warms the solution from (e).\n\nThe student concludes that ammonia gas is produced.\n\nState the observation that confirms ammonia gas is produced.
Identify a cation present in R other than calcium.
Solution R is prepared from a mixture of two different ionic compounds.\n\nSuggest the names of these two compounds.