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

Edexcel IGCSE Chemistry

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