Chemical Analysis Flashcards
(26 cards)
Pure substance
A single element or compound, not mixed with any other substance
E.g. gold, water, oxygen
Melting points of pure substances
The greater the difference in an objects melting point and the known pure melting point, the lower its purity
Formulations
A mixture that has been designed as a useful product
Chromatography
Separate mixtures and can give information to help identify substances
Rf value
Distance moved by substance / distance moved by solvent
Chromotography practical
Draw a pencil line across the chromatography paper, 1cm from the bottom
Use a pipette to add small spots of each ink to the line on the paper
Place the paper into a container with a suitable solvent in the bottom
Allow the solvent to move through the paper, but remove the chromatogram before it reaches the top
Allow the chromatogram to dry
Measure the distance travelled by each spot and by the solvent
Test for hydrogen
A burning splint held at the open end of a test tube of the gas
Hydrogen burns rapidly with a pop sound
Test for oxygen
The test for oxygen uses a glowing splint inserted into a test tube of the gas
The splint relights in presence of oxygen
Test for carbon dioxide
When carbon dioxide is shaken with or bubbled through limewater the limewater turns colourless to milky (cloudy)
Test for chlorine
Damp blue litmus paper turns red and is then is bleached turning white
Flame tests - Lithium
Results in a crimson flame
Flame tests - Sodium
Results in a yellow flame
Flame tests - Potassium
Results in a lilac flame
Flame tests - Calcium
Results in an orange-red flame
Flame tests - Copper
Results in a green flame
Test for metal hydroxides - aluminium
Add a few drops of dilute sodium hydroxide solution to the unknown solution
White precipitate forms and dissolves in excess sodium hydroxide solution
Metal hydroxides - calcium
Add a few drops of dilute sodium hydroxide solution to the unknown solution
White precipitate forms and their is no change when there is excess sodium hydroxide solution
Test for metal hydroxides - magnesium
Add a few drops of dilute sodium hydroxide solution to the unknown solution
White precipitate forms and their is no change when there is excess sodium hydroxide solution
Test for metal hydroxides - copper
Add a few drops of dilute sodium hydroxide solution to the unknown solution
Blue precipitate forms
Test for metal hydroxides - iron (II)
Add a few drops of dilute sodium hydroxide solution to the unknown solution
Green precipitate forms
Metal hydroxides - iron (III)
Add a few drops of dilute sodium hydroxide solution to the unknown solution
Brown precipitate forms
Test for carbonates
Add a dilute acid to an unknown substance in a boiling tube with a test tube containing limewater
Connect the two with a delivery tube and limewater turns cloudy in presence of CO₂
Test for halides
Add nitric acid, a few drops of silver nitrate and then the unknown solution
Silver chloride = white precipitate forms
Silver bromide = cream precipitate forms
Silver iodide = yellow precipitate forms
Test for sulfates
Add barium chloride and dilute HCl to the unknown solution
White precipitate forms
