Chemical testing

Question 1

Test and result for HYDROGEN

Answer 1

• hold a burning splint over a burning tube with the gas in it
• squeaky pop heard if hydrogen present

Question 2

Test and result for OXYGEN

Answer 2

• place a glowing splint into test tube of gas

- will relight if oxygen present

Question 3

Test and result for CARBON DIOXIDE

Answer 3

• bubble gas through limewater

- limewater turns cloudy

Question 4

Test and result for AMMONIA

Answer 4

• add sodium hydroxide solution
• heat
• test with damp litmus paper
  red litmus paper turns blue if ammonia present

Question 5

Test and result for CHLORINE

Answer 5

• place damp litmus paper into boiling tube of gas

- litmus paper is bleached and turns white

Question 6

Describe how to carry out a flame test

Answer 6

Take a sample of the metal on a wire and put it in a flame, the flame will turn a specific colour, showing what metal it is

Question 7

What is the flame colour of lithium

Answer 7

red

Question 8

What is the flame colour of sodium

Answer 8

yellow

Question 9

What is the flame colour of potassium

Answer 9

lilac

Question 10

What is the flame colour of calcium

Answer 10

orange/red flame

Question 11

What is the flame colour of copper

Answer 11

blue-green flame

Question 12

How to test for cations using precipitation reactions

Answer 12

• slowly add small amounts of sodium hydroxide solution and note what colour the precipitate formed is

Question 13

Colour of precipitate of copper (II)

Answer 13

blue

Question 14

Colour of precipitate of iron (II)

Answer 14

green

Question 15

Colour of precipitate of iron (III)

Answer 15

rust-coloured

Question 16

Colour of precipitate of ammonium

Answer 16

No precipitate, forms ammonia gas, then test gas to confirm (litmus paper turns blue)

Question 17

How to test for halide ions

Answer 17

• First add dilute nitric acid, followed by silver nitrate solution

Question 18

Why is nitric acid added to test for halide ions

Answer 18

to remove carbonate impurities

Question 19

Colour of precipitate of chloride ion

Answer 19

white/colourless precipitate of AgCl

Question 20

Colour of precipitate of bromide ion

Answer 20

cream precipitate of AgBr

Question 21

Colour of precipitate of iodide ion

Answer 21

yellow precipitate of AgI

Question 22

How to test for anions (sulphates)

Answer 22

First add dilute hydrochloric acid, followed by barium chloride solution

Question 23

Colour of precipitate of BaSO4

Answer 23

white/colourless precipitate

Question 24

How to test for anions (carbonates)

Answer 24

First add dilute hydrochloric acid which will create carbon dioxide, this can be bubbled through limewater and if goes cloudy then carbonate present

Question 25

How to test for water (chemical test)

Answer 25

add white anhydrous copper (II) sulphate and if water is present then copper sulfate goes from white to blue

Question 26

How to test for water (physical test)

Answer 26

measure boiling point (100*)

Question 27

What is a cation

Answer 27

a positively charged ion

Question 28

What is an anion

Answer 28

a negatively charged ion