Question

Barium and lead both produce yellow precipitate with the chromate ion as part of their confirmation tests. if you had a sample that possibly contained lead, barium, or both ions, outline a procedure for correctly identifying the cations present.

Answer 1

Explanation:

Lead belongs to group 1 cations and barium belongs to the fifth group cations.

If the sample, contains lead then it can be precipitated by using dilute HCl as lead chloride. Barium, if present will not precipitate.

Confirmatory test for lead:

Dissolve the precipitate in hot water and centrifugate and divide the filtrate in 3 parts as lead chloride comes in the solution because it is soluble in hot water.

• To the filtrate 1, add dilute sulfuric acid. The appearance of white precipitate confirms lead.
• To the filtrate 2, add 2-3 mL of potassium chromate solution. The appearance of yellow precipitate confirms lead.
• To the filtrate 3, add 2-3 mL of potassium iodide solution. The appearance of yellow precipitate confirms lead.

If barium is also present, it can be precipitated by using ammonium carbonate and can be confirmed by the addition of sulphurica cid which gives white precipitate and also addition of the potassium chromate solution. The appearance of yellow precipitate confirms barium. Also, barium imparts green color to the flame.

Answer 2

Barium is an element that is primarily used in fireworks because of its distinct green colour while on the other hand, lead is used in electrical industries due to its unique properties. The ions of these elements can simply be identified when its insoluble salts get precipitated by any process.