CHEMICAL ANALYSIS

Pure substances

- a single element or compound, not mixed with any other substance

- they melt and boil at specific temperatures

Formulations

- mixture that has been designed as a useful product

- many products are complex mixtures in which each chemical has a particular purpose

- made by mixing components in carefully measured quantities to ensure that the product has the required properties

Chromatography

- used to separate mixtures and give information to help identify substances

- involves a stationary phase and a mobile phase

- separation depends on the distribution of substances between phases

- RF VALUE= distance moved by substance/distance moved by solvent

Test for HYDROGEN

- use a BURNING SPLINT held at the open end of a test tube of the gas

- creates a 'SQUEAKY POP' sound

Test for OXYGEN

- use a GLOWING SPLINT inserted into a test tube of the gas

Splint RELIGHTS in oxygen

Test for CARBON DIOXIDE

- bubble the gas through LIMEWATER

- it will turn MILKY

Test for CHLORINE

- use DAMP LITMUS PAPER

- when damp litmus paper is put into chlorine gas, the litmus paper is BLEACHED AND TURNS WHITE

Flame test: LITHIUM TURNS...

Crimson

Flame test: SODIUM TURNS...

Yellow

Flame test: POTASSIUM TURNS...

Lilac

Flame test: CALCIUM TURNS...

Orange-red

Flame test: COPPER TURNS...

Green

Metal hydroxides

- aluminium, calcium & magnesium ions form s WHITE PRECIPITATE with NaOH

- only aluminium's precipitate dissolves when excess NaOH is added

- copper produces a BLUE PRECIPITATE

- iron (ii) produces a GREEN PRECIPITATE

- iron (iii) produces a BROWN PRECIPITATE

Carbonates

- carbonates react with dilute acids to create CARBON DIOXIDE

- this gas can be bubbled through limewater, if the limewater goes cloudy, the gas is CO2

Halides

- first add dilute nitric acid, followed by silver nitrate solution

- chloride gives a WHITE PRECIPITATE

- bromide gives a CREAM PRECIPITATE

- iodide gives a YELLOW PRECIPITATE

Sulfates

- add barium chloride solution

- a WHITE PRECIPITATE will form when sulfate ions are in this solution.