Qualitative Analysis Tests for Anions

What are the 5 methods of testing for cations

1. Testing for CO3(2-) using dilute acid and lime water

2. Testing for SO3(2-) using a di,Ute acid followed by potassium permanganate solution

3. Testing for sulfate SO4(2-) using barium chloride (BaCl2) solution followed by HCl

4. Testing for halides Cl, Br and I using silver nitrate and dilute nitric acid

5. Testing for nitrates, NO3 using aluminium (Devardas alloy) and sodium hydroxide

What’s the 4 step method when testing for CO3 (2-) using dilute acid and lime water

1. Put some of the unknown carbonate in a test tube. It can be a solid or liquid (in solution)

2. Add some acid (HCl, H2So4 or HNO3) using a pipette

3. Observe if there’s any effervescence

4. Collect a gas sample produced using a pipette and bubble it through lime water

What are the two anions and their observations

CO3 (2-) = effervescence

Co2 = turns lime water milky white

What is the 5 step method when testing for SO3 (2-) using potassium permanganate solution

1. Put some of the unknown sulfite in a solution, in a test tube

2. Add some dilute acid (HCl, H2So4, or HNO3) using a pipette

3. Observe if there’s effervescence

4. Collect a sample of gas produced using a pipette

5. Bubble gas through violet potassium permanganate solution

What are the 3 observations is SO3 (2-) is present

1. Effervescence occurs

2. The gas produced (SO2) is exposed to filter paper which has been soaked in acidified potassium dichromate (VI) solution. The filter paper turns from orange to green

3. The gas produced (SO2) can also be tested by using filter paper soaked in acidified potassium permanganate solution. If SO3 (2-) is present, the paper changes from purple to colourless

What’s the 4 step method when testing for SO4 (2-) when using BaCl2 solution followed by HCl

1. Put some of the unknown solution in a test tube

2. Add some barium chloride so,Union using a pioette

3. Observe the precipitate formed

4. Add some dilute HCl and shake the solution well

What’s the observation when a sulfate is present

A white precipitate forms which is insoluble in the acid

What’s the observation when a sulfite is present

White precipitate forms which is soluble in HCl. SO3 (2-) also reacts with HCl to produce a pungent smelling gas (SO2) and effervescence

What’s the observation when a carbonate is present

White precipitate forms which is soluble in HCl. The precipitate (BaCO3) reacts with HCl to produce CO2 gas (which turns lime water milky) and effervescence

What’s the 4 step method when testing for halides Cl, Br and I using silver nitrate and dilute nitric acid

1. Put some unknown solution in a test tube

2. Add some nitric acid using a pipette

3. Add silver nitrate solution with a pipette

4. Observe if a precipitate is formed

What’s the observation if a chloride is present

A white precipitate forms

What’s the observation if a bromide is present

A cream precipitate forms

What’s observed if an iodide is present

A yellow precipitate forms

What’s the 6 step method when testing for nitrates using aluminium (devardas alloy) and sodium hydroxide

1. Place a small volume of the onknown nitrate solution in a boiling tube

2. Add equal amounts of sodium hydroxide solution

3. Warm until the mixture boils

4. Keep damp red litmus paper near the mouth of the tube

5. If no reaction takes place add aluminium powder

6. Check the solution again using damp red litmus paper to observe any gases produced

What’s the observation when testing for ammonium (NH4)

Blue litmus turns red on hearing with NaOH only and ammonia gas is produced

What’s the observation when a nitrate is present

Blue litmus turns red on heating with NaOH and aluminium. Ammonia gas is also produced