Organic Tests

Question 1

Colourless liquid
Sharp/irritating smell

Observe colour and smell with caution

Answer 1

Possibly a carboxylic acid/ ethanoic acid

Question 2

Fruity/ sweet / solvent-like smell

Answer 2

Ester

Question 3

Solubility / miscibility in water - Testing for polarity of a liquid

Answer 3

Add a few cm3 of sample to deionised water in a test tube

Mixes with water / one layer = polar/ can H bond with water / possibly a carboxylic acid or alcohol

Does not mix with water / 2 layers = non-polar / no H bond with water

Question 4

Testing for carbon content by combustion

Answer 4

Place a few drops of liquid on watch glass
Ignite with a lit splint

Clean blue flame = low carbon compound/ possibly and alcohol

Sooty orange flame = high carbon content/ possibly alkane or alkene

Question 5

Testing for c=c alkene with bromine water

Answer 5

Add a few cm3 bromine water to the solution in a test tube

Orange –> Colourless = Alkene

Orange colour of Bromine water remains = no c=c

Question 6

Testing for halogen atoms in halogenoalkanes using silver nitrate solution and ethanol

Answer 6

Add 1cm3 of halogenoalkane to a few cm3 of ethanol
Add silver nitrate solution
Warm in a water bath

White ppt (slow to form) = chloroalkane

Cream ppt (faster than white ppt) = bromoalkane

Yellow ppt (reasonably fast) = iodoalkane

Question 7

Testing for -OH / Alcohol group using phosphorous pentachloride

Answer 7

Add a few PCl5 crystals to a few cm3 of liquid
Test any gas red leased with a glass rod dipped into conc ammonia solution

Gas released
Misty fumes
Solid disappears
Heat released
White smoke with conc NH3
= Alcohol , HCl gas released , white smoke is NH4Cl (ammonium chloride)

No gas released
No white smoke with conc NH3
= not an alcohol no -OH

Question 8

Colourless liquid

Alcohol smell

Answer 8

Possibly an alcohol