TESTS CHEM

test for ammonia NH4

add NAOH

warm gently

hold a damp red litmus paper

observaation - red litmus turns blue

equation- NH₄⁺(aq) + OH⁻(aq) → NH₃(g) + H₂O(l)

TEST FOR CARBONATE

add HCL

observation- effervescence {bubbling of gas} co2

CO₃²⁻(aq) + 2H⁺(aq) → CO₂(g) + H₂O(l)

test for sulfate

add acidified barium chloride bacl2

observation- white precipitate

Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

test for carbondioxide

bubble the gas thru limewater

white precipitate forms

CO₂(g) + Ca(OH)₂(aq) → CaCO₃(s) + H₂O(l)

test for magnesium oxide

add NAOH

white precipitate forms

Mg²⁺(aq) + 2OH⁻(aq) → Mg(OH)₂(s)

test for halide ions

add dilute nitric acid

add silveer nitrate solution

Agf- soluble so no visible change

Agcl - white precipitate Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

Agbr- cream precipitate Ag⁺(aq) + Br⁻(aq) → AgBr(s)

AgI- yellow precipitate Ag⁺(aq) + I⁻(aq) → AgI(s)

to distinguish bettween results from the test for halides what do we add

dilute ammonia- if its AgCL the white precipitate dissolves

then concentrated ammonia- if its AgBr cream precipitate dissolves

In the test for a halide ion, dilute nitric acid is added before silver nitrate. Why is nitric acid added? IMP Q

It prevents the precipitation of silver compounds other than halides.