Qualative Flashcards
Cu ionic equation qualitive
Cu+2+2OH- –> Cu(OH)2
Tests for carbonates
In a solution add dilute nitric acid to the solid or solution which is going to be tested. Bubble the gas through lime water and if there is carbon dioxide it will turn cloudy. This is when CO3 2- ions react with H+ to form CO2.
Test for sulphates. SO4 2-
Add aqueous Barium Chloride or Barium nitrate. If there are sulphate ions a white precipitate will form
Halide test
Add nitric acid then silver nitrate, AgNO3 to an aqueous solution of a halide. Silver chloride is white, silver bromide is cream and silver iodide is yellow. Add aqueous ammonia. If it is soluble in dilute NH3 it is a chloride. If it is soluble in concentrated NH3 it is a Bromide. If it is insoluble in concentrated NH3 then it is an Iodide.
Ionic equation of silver reacting with chlorine
Ag+(aq) + Cl-(aq) –> AgCl(s)
Sequence of tests
Carbonate, Sulphate then Halide.
Why do you test for Carbonate first
Neither sulfate nor halide ions produce bubbles with dilute acid. The carbonate test can be carried out without the possibility of an incorrect conclusion
Why do you test for sulfates second
Carbonate ions also produce a white precipitate with Barium. Therefore it is important to test for sulphate after you have tested for carbonate so that you don’t get a false positive
Why do you test for halides last
Silver carbonate and silver sulfate are both insoluble white solids and will form a precipitate. It is therefore important that you carry out the halide test last to rule out this possibility.
Test for Ammonium ions
Aqueous sodium hydroxide is added to a solution of Ammonium ions. The mixture is warmed and a gas is produced, this gas will turn ph paper blue.
Test for Iron (2)
Add sodium hydroxide a green precipitate forms
Ionic = Fe+2 + 2OH- –> Fe(OH)2
Test for Iron 3
Add sodium hydroxide a brown precipitate forms
Ionic = Fe+3 + 3OH- –> Fe(OH)3
Test for Cu
Add sodium hydroxide a blue precipitate forms
Ionic = Cu+2 + 2OH- –> Cu(OH)2
