ions test

Question 1

describe how to carry out a flame test

Answer 1

• dip a clean unreactive metal wire loop into a solid sample of the compound being tested
• put the loop into the edge of the blue flame from a Bunsen burner

Question 2

colour of flame for Lithium

Answer 2

Red

Question 3

colour of flame for Sodium

Answer 3

Yellow

Question 4

colour of flame for caucium/ Ca2+

Answer 4

Orange-Red

Question 5

colour of flame for copper/Cu2+

Answer 5

Blue-Green

Question 6

test for Cl-, Br-, I-

Answer 6

Acidify with dilute nitric acid and add aqueous silver nitrate.

Result: Chlorine - White precipitate formed
Bromide - Cream precipitate formed
Iodide - Yellow precipitate formed

Question 7

Test for carbonate (CO₃)

Answer 7

Add dilute acid and test the gas released

Result: Effervescence, gas produced CO2 which turns limewater cloudy.

Question 8

Test for Nitrate (NO3)

Answer 8

Add aqeuous NaOH and aluminium foil, warm gently and test for the gas released.

Result: Gas given off is ammonia, has a pungent smell and turns moist red litmus paper blue

Question 9

Test for Sulfate (SO4)

Answer 9

Acidify with dilute nitric acid and add aqeuous barium nitrate.

Result: White precipitate formed

Question 10

Test for ammonium ions

Answer 10

• Add a few drops of dilute sodium hydroxide solution
• Warm gently
• Ammonia gas will be released