Chemical tests.

Question 1

What is the test for sulphates (SO4 2-)?

Answer 1

HCl + BaCl2
Forms white precipitate (BaSO4)

Question 2

What is the test for carbonates (CO3 2-)?

Answer 2

Dilute HCl
Effervescence (CO2)

Question 3

What is the test for OH- ions?

Answer 3

Turns damp red litmus paper blue.

Question 4

What is the test for halide ions?

Answer 4

HNO3 + AgNO3
Nitric acid + Silver nitrate
Cl -> white ppt
Br -> cream ppt
l -> pale yellow ppt

Question 5

How can you differentiate between AgX halides?

Answer 5

Cl -> dissolves in dilute ammonia (NH3)
Br -> dissolves in conc. ammonia (NH3)
l -> insoluble in conc ammonia (NH3)

Question 6

What is the test for magnesium (Mg2+)?

Answer 6

NaOH
Forms white ppt (Mg(OH)2)
Insoluble in excess NaOH

Question 7

What is the test for calcium (Ca2+)

Answer 7

NaOH
Forms white ppt (Ca(OH)2)
Insoluble in excess NaOH

Question 8

How can you differentiate between Mg(OH)2 and Ca(OH)2?

Answer 8

Mg is insoluble in ammonia (NH3)
Ca is slightly soluble in ammonia (NH3)

Question 9

What is the test for Sr and Ba?

Answer 9

H2SO4
Forms white ppt (SrSO4) (BaSO4)

Question 10

How to differentiate between SrSO4 and BaSO4?

Answer 10

BaSO4 is less soluble

Question 11

What is the test for ammonia (NH4+)?

Answer 11

NaOH (warm)
Damp red litmus paper turns blue.

Question 12

What is the test for Co2+?

Answer 12

Ammonia (NH3)
Pink solution turns blue

Question 13

What is the test for copper (Cu2+)?

Answer 13

NaOH - pale blue ppt
NH3 - blue solution
Na2CO3 - green-blue ppt

Question 14

What is the test for iron(ll) (Fe2+)?

Answer 14

NaOH - green ppt (turns brown from oxidation)
NH3 - green ppt
Na2CO3 - green ppt

Question 15

What is the test for iron(lll) (Fe3+)?

Answer 15

NaOH -brown ppt
NH3 - brown ppt
Na2CO3 -brown ppt and effervescence

Question 16

What is the test for aluminium (Al2+)?

Answer 16

NaOH - white ppt (dissolves in excess NaOH to form a colourless solution)
NH3 - white ppt
Na2CO3 - white ppt and effervescence

Question 17

What colour flame does lithium produce?

Answer 17

Crimson

Question 18

What colour flame does sodium produce?

Answer 18

Yellow

Question 19

What colour flame does potassium produce?

Answer 19

Lilac

Question 20

What colour flame does calcium produce?

Answer 20

Orange-red

Question 21

What colour flame does copper produce?

Answer 21

Blue-green

Question 22

What is the test for alkenes?

Answer 22

Decolourises bromine water.

Question 23

What is the test for primary and secondary alcohols?

Answer 23

Acidified potassium dichromate (K2Cr2O7)
Orange solution turns green

Question 24

What is the test for tertiary alcohols?

Answer 24

Acidified potassium dichromate (K2Cr2O7)
Orange solution no change.

Question 25

What is the test for alcohols?

Answer 25

Metallic Na Produces effervescence (H2)

Question 26

What is the test for aldehydes?

Answer 26

Fehling's solution (warm) - Blue solution to a brick-red ppt. Tollens' reagent (warm) - Silver ppt formed (silver mirror).

Question 27

What is the test for carboxylic acids?

Answer 27

Add a carbonate CO2 released.

Question 28

What is the test for oxygen gas?

Answer 28

Relights a glowing splint.

Question 29

What is the test for hydrogen gas?

Answer 29

Lighted splint ignites with a squeaky pop.

Question 30

What is the test for carbon dioxide gas?

Answer 30

Turns limewater cloudy (calcium carbonate ppt).

Question 31

What is the test for chlorine gas?

Answer 31

Damp blue litmus paper turns red, then bleaches.

Question 32

What is the colour of the flame test for Strontium?

Answer 32

Red

Question 33

What is the colour of the flame test for Barium?

Answer 33

Pale green

Question 34

How do you perform a flame test?

Answer 34

Clean a nichrome/platinum wire by dipping it in HCl. Place the wire in the flame until no colour appears. Dip the wire in a sample of the metal compound. Place it in the edge of a blue flame.