Tests for organic and inorganic compounds

Question 1

Test for acid or base character

Answer 1

Use indicator paper
Acid turns paper red and alkali turns paper blue

Question 2

Flame test

Answer 2

Dip nichrome wire in conc HCl and then dip into metal ion solution. Place wire at the top of the Bunsen flame and observe colour.

Question 3

Carbonate/ hydrogen carbonate ions

Answer 3

Add aqueous acid
Bubbles of CO2 will be observed when bubbled through limewater. Limewater turned cloudy due to calcium carbonate ppt.

Question 4

Ammonium ions

Answer 4

Add aq NaOH and gently warm, the ammonia gas will turn indicator paper blue and pungent smell given off.

Question 5

Sulfate ions

Answer 5

Add acidified barium chloride solution and a white ppt is formed (barium sulfate)

Question 6

Halide ions

Answer 6

Add aq AgNO3 then aq NH3 solution
Cl- ion forms white ppt
Br- ion forms cream ppt
I- ion forms yellow ppt

Question 7

How would you confirm the presence of specific halide ions

Answer 7

Use ammonia to dissolve ppt
Cl- ions are soluble in dilute ammonia
Br- ions are soluble in conc ammonia
I- ions are insoluble in conc ammonia

Question 8

Li+ flame test colour

Answer 8

Red

Question 9

Na+ flame test colour

Answer 9

Orange

Question 10

K+ flame test colour

Answer 10

Lilac

Question 11

Rb+ flame test colour

Answer 11

Red

Question 12

Cs+ flame test colour

Answer 12

Blue

Question 13

Mg2+ flame test colour

Answer 13

No colour

Question 14

Ca2+ flame test colour

Answer 14

Brick red

Question 15

Sr2+ flame test colour

Answer 15

Crimson red

Question 16

Ba2+ flame test colour

Answer 16

Green

Question 17

Metal cation test

Answer 17

Use sodium hydroxide

Question 18

Mg2+ metal cation test

Answer 18

Some NaOH- white ppt
More NaOH- remains the same

Question 19

Ca2+ metal cation test

Answer 19

Some NaOH- White ppt (more soluble than Mg)
More NaOH- remains the same

Question 20

Zn2+ metal cation test

Answer 20

Some NaOH- White ppt that is soluble in NH3
More NaOH- Ppt dissolves into colourless solution

Question 21

Al3+ metal cation test

Answer 21

Some NaOH- White ppt
More NaOH- ppt dissolves into colourless solution

Question 22

Ag+ metal cation test

Answer 22

Dark brown ppt that does not dissolve in excess NaOH however is soluble in NH3

Question 23

Cu2+ metal cation test

Answer 23

Blue ppt that does not dissolve in excess NaOH

Question 24

Fe3+ metal cation test

Answer 24

Brown ppt that does not dissolve in excess NaOH

Question 25

Fe2+ metal cation test

Answer 25

White/green ppt slowly turns brown when exposed to the oxygen in the air

Question 26

Cr3+ metal cation test

Answer 26

Blue/green ppt that dissolves in excess NaOH to form a green solution

Question 27

Co2+ metal cation test

Answer 27

Blueish ppt that slowly turns pink, ppt does not dissolve in excess NaOH

Question 28

Ni2+ metal cation test

Answer 28

Green ppt formed that is insoluble in excess NaOH

Question 29

Mn2+ metal cation test

Answer 29

Off-white ppt that turns brown upon exposure to the air. Insoluble in excess NaOH

Question 30

Reaction between solid halide salt and conc sulfuric acid

Answer 30

Chloride produces steamy fumes of HCl Bromide produces steamy fumes, brown vapour Iodide produces steamy fumes, purple vapours, black solid

Question 31

Test for bromide

Answer 31

Add chlorine water to a solution of bromines, an orange solution is formed if present + effervescence

Question 32

Test for alkenes

Answer 32

Add bromine water and shake, colour change from orange to colourless if alkene present

Question 33

Test for -OH groups (but not phenols)

Answer 33

Add PCl5 and misty fumes of HCl will be observed Or add small piece of sodium and effervescence observed

Question 34

Test for carboxylic acids

Answer 34

Litmus paper turns red-ish Add sodium carbonate and observe effervescence

Question 35

Tests for aldehydes and ketones

Answer 35

Add 2,4-DNPH and an orange ppt is formed if aldehyde or ketone present (C=O bond)

Question 36

Test for aldehyde

Answer 36

Add Tollen's reagent (AgNO3) Silver mirror observed if aldehyde present, ketones do not change as they cannot be oxidised

Question 37

Test for ketone

Answer 37

Fehlings Solution Aldehydes- brick red ppt Ketones- No change, remains deep blue solution

Question 38

Iodoform reaction test

Answer 38

Warm with iodine and NaOH and observe yellow ppt and antiseptic smell.

Question 39

Alcohol (primary and secondary) and aldehyde

Answer 39

Warm with acidified sulfuric acid and potassium dichromate Colour change from orange to green

Question 40

Esterification test

Answer 40

Gently warm alcohol and carboxylic acid in the presence of conc sulfuric acid, produces a compound with a characteristic smell e.g pineapples.