Organic Tests

Question 1

Flame tests (Group 1 and 2)

Answer 1

Lithium = red
Sodium = orange/yellow
Potassium = lilac
Rubidium = red 
Ceasium = blue 
Calcium = Brick red
Strontium = crimson 
Barium = apple green

Question 2

Test for aldehydes

Answer 2

Tollens reagent - colourless to silver mirror
Fehlings/benedicts - blue to brick red
Acidified dichromate ions - orange to green

Question 3

Test for carbonyl group

Answer 3

Brady’s/24DNP - blue to orange

Question 4

Test for double bond

Answer 4

Decolourises bronine water

Question 5

Test fi methyl cabonyl

Answer 5

Heated with I2 in alkain conditions a yellow ppt forms

Question 6

[O] oxidising agents

[H] reducing agents

Answer 6

[O] K2Cr2O7/H2SO4

[H] LiAlH4/ Tin +conc HCl

Question 7

Test for SO4 2-

Answer 7

Add dilute HCl followed by BaCl2 > BaSO4 (White Ppt)

Question 8

Test for NH4 +

Answer 8

Add NaOH and gently heat. Then test gas produced by putting damp litmus paper - if it turns blue there is NH3 present.

Question 9

Test for X- ion

Answer 9

Add HNO3 and AgNO3 to form
White ppt is chlorine - AgCl
Cream ppt is bromoine - AgBr
Yellow ppt is iodine - AgI

Question 10

24DNP used to distinguish ketone and aldehyde

Answer 10

Both form orange ppt.
Then recrystalise.
Determine the melting points.
Compare with data book.

Question 11

What colour is NO2 gas

Answer 11

Dark red/brown

Question 12

Types of drying eather

Answer 12

(Anhydrous)
Sodium sulfate
Calcihm chloride
Magnesium sulfate

When surfficent ammount has been added it becomes transparent and stops clumping.

Question 13

Appearance chnage when drying somwthing

Answer 13

Cloudy to clear

Question 14

Method of recrystilsation

Answer 14

Disolve in hot water.
Filter quickly to remove insoluable impurities.
Allow solution to cool and crystallize.
Filter from remaining solution to remove soluable impurities.
Wash crystals to ensure no impuritoes dry on it.
Leave to dry

Question 15

Colour of MnO4-

Answer 15

Purple