Test-Tube Tests Flashcards
What does Bromine Water test for?
Observation?
Alkene
Orange - Colourless
Why does Bromine water go colourless?
Electrophilic addition of Br2 to alkene
What does acidified K2Cr2O7 test for?
Observation?
Primary Alcohol, Secondary Alcohol, Aldehyde
Orange - Green
Why is there a colour change in K2Cr2O7?
Cr2O7(2-) reduced to Cr(3+) when alcohol/aldehyde oxidised
What does Tollen’s reagent test for?
Observation?
Aldehydes
Silver mirror forms
Why does Tollen’s reagent form silver mirror?
Ag+ in Tollens reagent is reduced to Ag when aldehyde oxidised
What does Fehling’s solution test for?
Observation?
Aldehydes
Brick red precipitate forms
Why does Fehling’s solution form a precipitate?
Fehling’s solution reduced when aldehyde oxidised
What does Sodium Carbonate test for?
Observation?
Carboxylic Acid
Effervescence
Why does Sodium Carbonate cause effervescence?
Forms CO2
What tests for Ba2+?
Observation?
Reason for Observation?
Equation?
H2SO4
White precipitate
Formation of BaSO4 (s)
Ba(2+) + SO2(2-) —-> BaSO4
What tests for SO4(2-)?
Observation?
Reason for Observation?
Equation?
Acidified BaCl2
White precipitate
Formation of BaSO4 (s)
Ba(2+) + SO2(2-) —-> BaSO4
What tests for Mg2+?
Observation?
Reason for Observation?
Equation?
NaOH
White precipitate
Formation of Mg(OH)2
Mg2+ + 2OH- —-> Mg(OH)2
What tests for OH-?
Observation?
Reason for Observation?
Equation?
MgCl2
White precipitate
Formation of Mg(OH)2
Mg2+ + 2OH- —-> Mg(OH)2
What tests for Cl-?
Observation?
Reason for Observation?
Equation?
AgNO3
White precipitate
Formation of AgCl
Ag+ + Cl- —-> AgCl
What tests for Br-?
Observation?
Reason for Observation?
Equation?
AgNO3
White precipitate
Formation of AgBr
Ag+ + Br- —-> AgBr
What tests for I-?
Observation?
Reason for Observation?
Equation?
AgNO3
White precipitate
Formation of AgI
Ag+ + I- —-> AgI
What tests for AgCl?
Observation?
Equation?
Dilute NH3
AgCl precipitate dissolves
AgCl + 2NH3 —-> [Ag(NH3)2]+ + Cl-
What tests for AgBr?
Observation?
Equation?
Concentrated NH3
AgBr precipitate dissolves
AgBr + 2NH3 —-> [Ag(NH3)2]+ + Br-
What tests for NH4+?
Observation?
Reason for Observation?
Equation?
Heat with NaOH
Gas released turns damp red litmus paper blue
Formation of NH3 (g)
NH4+ + OH- —-> NH3 + H2O
What tests for CO3(2-)?
Observation?
Reason for Observation?
Equation?
Acid (any) (HNO3 works best)
Effervescence
Formation of CO2 (g)
2H+ + CO3(2-) —-> H2O + CO2 (acid+carbonate base —-> salt+water+CO2)
