Qualitative analysis Flashcards
(14 cards)
Describe the test/result for Cl- ions
Add Silver Nitrate (AgNO3), a white precipitate of AgCl will form, which is soluble in dilute and concentrated ammonia
Describe the test/result for Br- ions
Add Silver Nitrate (AgNO3), a cream precipitate of AgBr will form which is insoluble in dilute ammonia and soluble in concentrated ammonia
Describe the test/result for I- ions
Add Silver Nitrate (AgNO3), a yellow precipitate of AgI will form, which is insoluble in dilute and concentrated ammonia
Describe the test and result for Sulphate ions
Add Barium chloride or nitrate, a white precipitate will form.
Describe the test and result for carbonate ions
Add a small amount of acid (HCl), effervescence will occur. Running the gas through limewater (dissolved calcium hydroxide) will cause a white precipitate of calcium carbonate to form
Describe the test and result for ammonium ions
React with warm sodium hydroxide, the resulting gas produced will turn litmus paper blue.
What is the equation in the primary test tube in the carbonate ion test?
CO32- (aq) + 2H+ (aq)→CO2 (g) + H2O (l)
What is the equation in the secondary test tube in the carbonate ion test?
CO2 (g) + Ca(OH)2 (aq) → CaCO3 (s) + H2O (l)
What is the equation for the sulphate ion test?
Ba2+ (aq) + SO42- (aq) → BaSO4 (s)
What is the general equation for the halide ion tests?
X-(aq) + Ag+(aq) → AgX (s)
What is the equation for the test for ammonium ions?
NH4+ (aq) + OH- (aq) → NH3 (g) + H2O (l)
What gives false positives when added to AgNO3 (aq)? What is the associated equations?
Sulphate and carbonate ions.
2Ag+(aq)+SO42-(aq) →Ag2SO4(s)
2Ag+(aq)+CO3-(aq) →Ag2CO3-(s)
What do we add to remove false positives when added to AgNO3 (aq)
HNO3 (aq)
How do we identify a carbonyl group?
If we have 2 positive results, how could we distinguish between them?
Add 2,4- DNP, +ve result is red/orange/yellow ppt
Compare the melting points with reference values.
