chemical analysis

what is a pure substance

a single element or compound that contains no other substances

what is a formulation

a mixture that has been designed as a useful product

what is chromatography used for

to separate substances and provide information to help identify them

chromatography practical

1. set up chromatography paper

2. lower paper into a beaker with appropriate solvent. wait for solvent to travel up the paper

3. analyse chromatogram

what is the mobile phase

the mobile phase is the solvent

what is the stationary phase

the chromatography paper

which substances will travel further up the paper

the substances which are more soluble in the solvent will travel further up the paper

why do the more soluable substances travel further

they spend more time in the mobile phase and are thus carried further up the paper than the less soluable components

how many spots will a pure substance produce on the chromatography paper

only one spot

how to calculate the Rf value

distance moved by the substance

/ distance moved by solvent

what does the Rf value allow chemists to identify

unknown substances because it can be compared with Rf values of known substances under the same conditions

test for hydrogen

1. holding a burning splint

2. burns with a loud squeaky pop

test for oxygen

relights a glowing splint

test for carbon dioxide

makes limewater cloudy

test for chlorine

bleaches damp blue litmus paper

will turn red then bleached white

colour flame of lithium

crimson

colour flame of sodium

yellow

colour flame of potassium

lilac

colour flame of calcium

orange- red

colour flame of copper

green