Use a copy of the Periodic Table where you need one.
Which cation gives a white precipitate with aqueous sodium hydroxide that is insoluble in excess?
Source: Learners' Alley, Qualitative Analysis slides
A solution is acidified with dilute nitric acid, then aqueous silver nitrate is added. A yellow precipitate forms. Which ion is present?
Source: Learners' Alley, Qualitative Analysis slides
A pungent gas turns damp blue litmus paper red, then bleaches it. What is the gas?
Source: Learners' Alley, Qualitative Analysis slides
Answer these questions about qualitative analysis.
Source: Learners' Alley, Qualitative Analysis slides
When sulfur is burned, sulfur dioxide is produced. How can the identity of sulfur dioxide be confirmed?
| test | observation | |
|---|---|---|
| A | insert a glowing splint into the gas | the glowing splint rekindles |
| B | use a piece of damp blue litmus paper | blue litmus paper turns red and is then bleached |
| C | use a piece of damp red litmus paper | red litmus paper turns blue and is then bleached |
| D | use a piece of filter paper soaked with acidified potassium manganate(VII) | purple potassium manganate(VII) turns colourless |
Source: 2023 GESS Sec 3 End-of-Year P1 Q34
Separate tests were performed on an unknown solution. The results are shown in the table. What is the unknown solution?
| test | observation |
|---|---|
| add aqueous sodium hydroxide | green precipitate forms and is insoluble in excess sodium hydroxide |
| add nitric acid | no observable change |
| add aqueous sodium hydroxide, aluminium foil and warm | pungent gas evolved which turned moist red litmus paper blue |
Source: 2023 GESS Sec 3 End-of-Year P1 Q35
An excess of aqueous sodium hydroxide is added to an aqueous solution of salt X and boiled. Ammonia gas is only given off after aluminium foil is added to the hot solution. What could X be?
Source: 2024 CHS Sec 3 End-of-Year Section A Q27
There are two unlabelled test tubes. One contains aqueous ammonium nitrate and the other contains aqueous sodium nitrate. Which test could identify the solutions?
Source: 2020 SJI Year 3 End-of-Year P1 Q20
Three substances were added separately to aqueous potassium sulfate and to aqueous potassium carbonate.
1 aqueous ammonia
2 barium nitrate solution
3 dilute hydrochloric acid
Which substance(s) would give different observations with the two solutions?
Source: 2020 SJI Year 3 End-of-Year P1 Q19
A solution of compound Z reacts with sodium hydroxide solution to form a white precipitate that is insoluble in excess sodium hydroxide solution. Aluminium powder is then added. The mixture is heated and a gas that turns damp red litmus paper blue is given off. What could Z be?
Source: 2024 CHIJ Prelim P1 Q18
Aqueous ammonia is commonly used to identify cations which are present in salt solutions.
Source: 2021 SJI Prelim P2 A2(b)
Describe what you see when:
Source: 2025 TKGS Prelim P2 Q(c)
Bcalcium, Ca2+[1]
The white precipitates of aluminium and zinc hydroxide dissolve in excess aqueous sodium hydroxide. Ammonium ions give no precipitate.
Biodide, I−[1]
Silver iodide is yellow. Silver chloride is white, sulfate is tested with barium nitrate, and any carbonate is removed by the nitric acid.
Cchlorine[1]
Chlorine is acidic and also bleaches. Ammonia turns red litmus blue, carbon dioxide is odourless, and sulfur dioxide is tested with acidified potassium manganate(VII).
A red-brown precipitate, insoluble in excess. [1]
Acidify with dilute nitric acid, then add aqueous barium nitrate: a white precipitate forms. [1]
Hold a lighted splint at the mouth of the tube: it is extinguished with a pop. [1]
Aqueous ammonia (in excess). [1]
Dacidified potassium manganate(VII) turns from purple to colourless[1]
Sulfur dioxide turns acidified potassium manganate(VII) from purple to colourless. A is the test for oxygen and B is the test for chlorine.
Ciron(II) nitrate[1]
The green precipitate shows iron(II) ions. No effervescence with nitric acid means no carbonate, and ammonia with aluminium foil shows nitrate ions.
Dsodium nitrate[1]
No ammonia before the aluminium is added, so there are no ammonium ions. Ammonia after adding aluminium shows nitrate ions.
Badd aqueous sodium hydroxide and warm[1]
Only ammonium nitrate gives ammonia when warmed with aqueous sodium hydroxide. With aluminium foil, both nitrates would give ammonia.
B3 only[1]
Aqueous ammonia gives no change with either. Barium nitrate gives a white precipitate with both (barium sulfate and barium carbonate). Only hydrochloric acid gives effervescence, with the carbonate.
Ccalcium nitrate[1]
A white precipitate insoluble in excess shows calcium ions. Ammonia after adding aluminium shows nitrate ions.
Add aqueous ammonia dropwise, then in excess: a green precipitate forms which is insoluble in excess. [1]
Fe2+(aq) + 2OH−(aq) → Fe(OH)2(s): correct ionic equation [1]
Correct state symbols [1]
A light blue precipitate. [1]
The light blue precipitate dissolves in excess aqueous ammonia, giving a dark blue solution. [1]