GCSE Chemistry Chemical Analysis

Purity

something that only contains one compound or element throughout

boiling point

a chemically pure substance will melt or boil at a specific temperature - you can test for a substances purity by comparing it with the boiling point of that pure substance

Formulations

useful mixtures with a precise purpose - each component is measured exactly and contributes to the properties of the formulation

formulation of paint

pigment, solvent, binder, additives

Paper chromatography

mobile phase = where the molecules can move, this is always a liquid or a gas

stationary phase = where the molecules can't move - a solid or thick liquid

mobile phase

the chemical that spends more time in the mobile phase will move further through the stationary phase

high solubility molecules

will spend more time in the mobile phase

Rf Value

distance travelled by substance/distance travelled by solvent

test for chlorine

chlorine turns damp litmus paper white

test for oxygen

relight a glowing splint

test for carbon dioxide

when bubbled through lime water it will turn it cloudy

test for carbonates

adding dilute acid, then bubble the gas that is given off through lime water - if it is a carbonate the gas will be carbon dioxide

test for sulphates

using a pipette add a few drops of dilute hydrochloric acid then some barium chloride solution

if a sulphate is present, a white precipitate will form= bariumsulfate

test for halides

to identify a halide ion, add dilute nitric acid then silver nitrate solution

a chloride = white precipitate = silver chloride

a bromide - cream precipitate = silver bromide

a iodide = yellow precipitate = silver iodide

lithium

crimson flame

sodium

yellow flame

potassium

lilac flame

calcium

orange red flame

copper

green flame

Metals with sodium hydroxide

calcium = white

Copper = blue

Iron II = Green

Iron III = Brown

Aluminium = white (dissolves in excess - colourless)

Magnesium - white

Flame emission spectroscopy

sample in flame, electrons become excited, when they drop back to their energy levels they transfer energy as light - spectroscope can detect different wave lengths of light - line spectrum

wavelengths depend on the charge

intensity of the spectrum indicates the concentration of the ion in the solution