Na2SO4 and K2SO4 solutions are neutral and colourless.
Sulfate ion exists as many compounds. Some of them dissolve in water and some of them make white or different colour precipitates. Sulfate compounds of 3d metals show colours. Sulfuric acid ( H2SO4 ) is a strong acid and completely dissociate in water to sulfate ion and two hydrogen plus ions. H2SO4 is a dibasic acid.
All sulfates of
are solutions and colourless too.
Examples: Na2SO4, K2SO4
CaSO4 is somewhat soluble in water. When ion concentration is low, it is soluble. When ion concentration is high, it forms a white precipitate.
BaSO4 , SrSO4 , PbSO4 are sparingly soluble in water and form white precipitates.
Following experiments are conducted to test occurrence of sulfate ion.
BaSO4, white precipitate forms. BaSO4 is not soluble in strong acids.
Strontium chloride ( SrCl2 ) gives white precipitate ( SrSO4 ) with sulfate ion solutions. SrSO4 is insoluble in acids.
AgNO3 does not form a precipitate with dilute sulfate solutions. Silver sulfate (Ag2SO4) is fairly soluble in water. However concentrated Ag2SO4 solution may be deposited as a precipitate.
If Ca2+ and SO42- ions concentration in the water are high, a white precipitate ( CaSO4 ) forms. When adding water, precipitate dissolve to give a colourless solution again.
When sodium sulfate is added to the lead acetate aqueous solution, lead sulfate (PbSO4), white precipitate is given. PbSO4 is soluble in caustic alkalis and in ammonium acetate solutions. But PbSO4 is not soluble in dilute acids.
In here, we are going to study solubility and colours of 3d metal sulfate compounds.
Manganese sulfate is a white orthorhombic crystals at solid state. MnSO4 dissolves in water.
Aqueous copper sulfate solution is blue colour. But when dehydrated copper sulfate is white a powder.
Add barium chloride to dilute sulfuric acid. It will give a white precipitate strontium sulfate. Separate the precipitate from the solution. Then add dilute acid such as HCl to the precipitate. Pricipitate does not dissolve. SO that says us there were sulfate ions in the initail solution.
Think, there are two colourless solutions. One solution contains sulfate ion and other one has sulfite ion. You are said to identify which solution have sulfate ion.
Add barium chloride to both solutions separately. You can see a forming white precipitates in both solutions.
Add dilute HCl to the both solutions. Then one precipitate dissolves and give colourless solution. That is for solution which contains sulfite ion.
There are two two solids and your teacher said that one of them is calcium carbonate and other one is calcium sulfate. Now you have to identify which solid is calcium carbonate by doing some tests.
This can be done by simple experiment. Add both solids to little amount two water samples separately. Two white precipitates form. Now add water to both flask. At one moment you can see, one white precipitate dissolve completely and give colourless solutions. That is calcium sulfate.
You cannot identify sulfate ion from dilute HCl. If sulfate ion exists as a precipitate, it does not dissolve in dilute HCl.
But if metal ion has a abililty to make a precipitate with chloride ion, we can see a precipitate is forming in the solution.
When dilute HCl is added to the aqueous silver sulfate solution, a white precipitate (silver chloride - AgCl) is given.
Lithium sulfate is soluble in water and it completely decomposes to lithium and sulfate ion.
Qualitative Analysis for anions and cations for Grade 12 ClassEmission of gases Identify ammonium salts identify d block cations by ammonia solution Identify halides Identify carbonate ions identify chromium compounds Testing for thiosulfate (S2O32-) Testing for phosphate ion