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

if continuing to test for sulfates and halides, dont use sulfuric acid (will show positive in sulfate test) or hydrochloric acid (will show positive in halides test)

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)