Question

Chemistry 2 Lab question!

How is sulfate ion seperated from NO3 - and Cl - ?

Answer 1

Chemical Separation by Precipitation

A mixture of metal ions in a solution can be separated by precipitation with anions such as Cl^-, Br^-, SO₄^2-, CO₃^2-, S^2-, Cr₂O₄^2-, PO₄^2-, OH^- etc. When a metal ion or a group of metal ions form insoluble salts with a particular anion, they can be separated form others by precipitation.

We can also separate the anions by precipitating them with appropriate metal ions.

There is no definite dividing lines between insoluble salts, sparingly soluble, and soluble salts, but concentrations of their saturated solutions are small, medium, and large. Solubility products are usually listed for insoluble and sparingly soluble salts, but they are not given for soluble salts. Solubility products for soluble salts are very large.

What type of salts are usually soluble, sparingly soluble and insoluble? The following are some general guidelines, but these are not precise laws.

• All nitrates are soluble. The singly charge large NO₃^- ions form salts with high solubilities. So do ClO₄^-., ClO₃^-, NO₂^-, HCOO^-, and CH₃COO^-.
• All chlorides, bromides, and iodides are soluble except those of Ag⁺, Hg₂²⁺, and Pb²⁺. CaF₂, BaF₂, and PbF2 are also insoluble.
• All sulfates are soluble, except those of Ba²⁺, Sr²⁺, and Pb²⁺. The doubly charged sulfates are usually less soluble than halides, and nitrates.
• Most singly charge cations K⁺, Na⁺, NH₄⁺ form soluble salts. However, K₃Co(NO₂)₆ and (NH₄)₃Co(NO₂)₆ are insoluble.

These are handy rules for us to have if we deal with salts often. On the other hand, solubility is an important physical property of a substance, and these properties are listed in handbooks.

You can use Barium to precipitate the sulfate ion. regards!