CL 8- qualitative analysis

Question 1

order for testing anions

Answer 1

1. carbonates
2. sulfates
3. halides
   must test carbonates first as adding barium chloride to a carbonate also produces a white precipitate (reduces chance of false positive of sulphates)

Question 2

testing for carbonates

Answer 2

add acid, carbonates fizz

Question 3

ionic equation for carbonates

Answer 3

CO₃²⁻ + 2H⁺ –> CO₂ + H₂O

Question 4

testing for sulfates

Answer 4

add barium nitrate or barium chloride, forms white precipitate

Question 5

ionic equation for sulfates

Answer 5

SO₄²⁻ + Ba²⁺ –> BaSO₄

Question 6

testing for halides

precipitates and solubilities

Answer 6

add AgNO₃
chloride- white precipitate
bromide- cream precipitate
iodide- yellow precipitate

solubility in NH₃
chloride- soluble in dilute
bromide-soluble in concentrated
iodide- insoluble

Question 7

ionic equation for halides

Answer 7

Ag⁺ + X⁻ –> AgX

Question 8

testing for ammonium

Answer 8

add NaOH and heat
damp red litmus paper held above test tube will turn blue (as ammonia gas is released which is alkaline)