chemical analysis (2)

Question 1

how is substance purity identified-

Answer 1

boiling/ melting points

Question 2

what are formulations

Answer 2

mixtures with exact amounts of components

Question 3

paper chromatography-

Answer 3

separates substances in a mixture

mobile phase- where molecules can move, a liquid or gas
stationary phase- where molecules can’t move, solid or thick liquid

substances move between both phases
substances that spend more time in the mobile phase move further (how soluble they are and attraction to the paper determines this)
substances separate by whether they move further or not from the stationary phase

Question 4

Rf value-

Answer 4

Rf value- distance travelled by substance/ distance travelled by the solvent

Question 5

test for chlorine-
test for oxygen-
test for carbon dioxide-
test for hydrogen-

Answer 5

test for chlorine- bleaches damp blue litnus paper white
test for oxygen- relights a glowing splint
test for carbon dioxide- turns limewater cloudy
test for hydrogen- squeaky pop

Question 6

Flame tests for:
Lithium-
Sodium-
Potassium-
Calcium-
Copper-

Answer 6

Lithium- crimson
Sodium- yellow
Potassium- lilac
Calcium- orange-red
Copper- green

Question 7

Precipitate colour with NaOH:
calcium-
copper-
iron(ii)-
iron(iii)-
aluminium-
magnesium-

Answer 7

calcium- white
copper- blue
iron(ii)- green
iron(iii)- brown
aluminium- white then colourless
magnesium- white

Question 8

Flame spectroscopy-

Answer 8

the light from a flame passes through the spectroscope
the different wavelengths from each metal are detected
the graph can be analysed to determine which ions were present
the intensity of the spectrum indicates the concentration of the ion

Question 9

benefits of machine analysis-

Answer 9

very sensitive
very fast
very accurate

Question 10

test for carbonates-
test for sulphates-
test for halides (chloride, bromide, iodide) -

Answer 10

test for carbonates- react substance with hydrochloric acid. If CO2 is made and turns limewater cloudy, the solution has carbonates

test for sulphates- react solution with hydrochloric acid and barium chloride. A white precipitate forms in the presence of sulfate ions

test for halides- react solution with nitric acid and silver nitrate

chloride- white precipitate of silver chloride forms
bromide- cream precipitate of silver bromide forms
iodide- yellow precipitate of silver iodide forms