Analysis of Unknowns

Question 1

Test for carbonate and hydrogencarbonate ions?

Answer 1

Add dilute HCl to form co2 then use limewater

Question 2

Test for sulfates

Answer 2

Add dilute HCl then barium chloride solution.

White ppt of barium sulfate forms (BaSO4)

Question 3

Test for ammonium compounds

Answer 3

Add NaOH and heat mixture

Use damp litmus paper and litmus turns blue if ammonia present

Question 4

Lithium flame colour

Answer 4

Scarlet red

Question 5

Sodium flame colour

Answer 5

Yellow

Question 6

Potassium flame colour?

Answer 6

Lilac

Question 7

Caesium flame colour?

Answer 7

Blue

Question 8

Calcium flame colour

Answer 8

Brick red

Question 9

Barium flame colour

Answer 9

Green

Question 10

Strontium flame colour

Answer 10

Red

Question 11

Rubidium flame colour

Answer 11

Red

Question 12

G2 Hydroxides solubility test

Answer 12

add dilute NaOH. Mg(OH)2 is insoluble and forms a white ppt. Ca(OH)2 is partially soluble and forms a white ppt with a lot of excess NaOH. the other hydroxides are fully soluble.

Question 13

Test for halides with ammonia solution.

Answer 13

AgCl dissolves in dilute ammonia. AgCl dissolves in concentrated ammonia while AgI is insoluble

Question 14

Test for alkenes?

Answer 14

add bromine water, orange to colourless

Question 15

test for carbonyls?

Answer 15

2,4-DNP forms an orange ppt with carbonyls

Question 16

Test for aldehydes: Tollens

Answer 16

silver mirror forms when heated.

Question 17

Test for aldehydes: Fehlings

Answer 17

blue solution to brick red ppt. Cu2+ ions change to Cu2O solid ppt.

Question 18

Reaction of carbonyls with I2 in presence of alkali

Answer 18

CHI3 is produced, a yellow crystalline ppt

only occurs with carbonyls that have a methyl group next to the C=O bond.

Question 19

Test for carboxylic acids?

Answer 19

add NaCO3 and effervescence occurs as CO2 is produced.