2h) Inorganic Chemistry - Chemical Tests (2.44 - 2.50)

Edexcel IGCSE Chemistry

2.44 - TESTS FOR GASES

2.44 - TESTS FOR GASES

2.44 - TESTS FOR GASES

test for hydrogen

• place lit splint in test gas

• burns with a ‘squeaky pop’ sound

test for oxygen

• place glowing splint in test tube

• splint relights

test for carbon dioxide

• bubble through limewater

• lime water tunrs milky/cloudy

test for ammonia

damp red litmus paper turns blue

test for chlorine

damp blue litmus paper is bleached

2.45 - Describe how to carry out a flame test

• dip nichrome wire in concentrated hydrochloric acid then into test solid

• Put in blue/roaring flame of Bunsen burner

• colour of the flame identifies the metal ion present

2.46 - FLAME TESTS

2.46 - FLAME TESTS

what is the colour of the flame for lithium (Li+)?

red

what is the colour of the flame for sodium (Na+)?

yellow

what is the colour of the flame for potassium (K+)?

lilac

what is the colour of the flame for calcium (Ca 2+)?

oragne-red

what is the colour of the flame for copper (Cu2+)?

blue-green

2.47 - TESTS FOR CATIONS

2.47 - TESTS FOR CATIONS

how are metal cations identified?

by the colour of the precipitate they form using sodium hydroxide solution

result of test for ammonium

ammonia gas produced turns damp red litmus paper blue

result of test for copper

light blue precipitate formed

result of test for iron (II)

green precipitate formed

result of test for iron (III)

red-brown precipitate formed

2.48 - TESTS FOR ANIONS

2.48 - TESTS FOR ANIONS

test for carbonate

• add dilute hydrochloric acid and test the gas released

• result - effervescence, gas produced is CO2 (turns limewater milky)

test for chloride

• acidify with dilute nitric acid and add silver nitrate solution

• result - white precipitate formed

test for bromide

• acidify with dilute nitric acid and add silver nitrate solution

• result - cream precipitate formed

test for iodide

• acidify with dilute nitric acid and silver nitrate solution

• result - yellow precipitate formed

test for sulfate

• acidify with dilute hydrochloric acid and add aqueous barium chloride

• result - white precipitate formed

2.49 - Chemical Test for Water

• anhydrous copper sulfate truns from white to blue on addition of water,

• product = hydrated copper sulfate

2.50 - Physical test for water

• check its boiling point

• pure water - boiling point is exactly 100 degrees celsius

• any impurites will raise/decrease boiling point