Uploaded June 2020 | Updated September 2026, 2 weeks ago
In this demonstration, you will be introduced to three classic precipitation reactions.
copper(II) sulfate + sodium hydroxide → copper(II) hydroxide + sodium sulfate
Copper(II) hydroxide is insoluble in water. This is seen as a blue precipitate. The remaining ions (sodium and sulfate) have remained in solution: they are often called spectator ions.
lead(II) nitrate + potassium iodide → lead(II) iodide + potassium nitrate
Lead(II) iodide is insoluble in water. This is seen as a bright yellow precipitate. The spectator ions in this example are nitrate and potassium. Lead(II) iodide was once used to make yellow paint, but this has been discontinued due to its toxicity.
cobalt(II) chloride + sodium carbonate → cobalt(II) carbonate + sodium chloride
Cobalt(II) carbonate is insoluble in water. This is seen as a purple precipitate. The spectator ions in this example are chloride and sodium. Cobalt(II) carbonate is often taken as a dietary supplement by vegans. Cobalt is required to make vitamin B12 and is normally obtained by eating animals or animal sourced products, like milk and eggs. Marmite is also a good source of cobalt.
In this demonstration, you will be introduced to three classic precipitation reactions.
copper(II) sulfate + sodium hydroxide → copper(II) hydroxide + sodium sulfate
Copper(II) hydroxide is insoluble in water. This is seen as a blue precipitate. The remaining ions (sodium and sulfate) have remained in solution: they are often called spectator ions.
lead(II) nitrate + potassium iodide → lead(II) iodide + potassium nitrate
Lead(II) iodide is insoluble in water. This is seen as a bright yellow precipitate. The spectator ions in this example are nitrate and potassium. Lead(II) iodide was once used to make yellow paint, but this has been discontinued due to its toxicity.
cobalt(II) chloride + sodium carbonate → cobalt(II) carbonate + sodium chloride
Cobalt(II) carbonate is insoluble in water. This is seen as a purple precipitate. The spectator ions in this example are chloride and sodium. Cobalt(II) carbonate is often taken as a dietary supplement by vegans. Cobalt is required to make vitamin B12 and is normally obtained by eating animals or animal sourced products, like milk and eggs. Marmite is also a good source of cobalt.
