C8 Chemical Analysis Flashcards
(31 cards)
Pure substance
A single element of compound not mixed with any other substance
Mixture
Consists of 2 or more elements of compounds not chemically combined together. The chemical properties of each substance in the mixture is unchanged
Separation processes
Filtration Crystallisation Distillation Fractional distillation Chromatography
Pure and impure substances
Boiling and melting point used to see if it is pre or not
Impure substances will have a lower melting point and melt over a broad range of temperatures
Pure substances it will melt more sharply at a specific temperature
Impure boiling point is higher than pure substance
Formulation
Is a mixture that has been designed as a useful product
Eg. Paints, alloys, fertilisers and food like ketchup
Purpose of component chemicals
To improve the quality of a product
Making an alloy
Adding different amounts of nutrients to make the fertiliser the most effective
Many products are complex mixtures in which each chemical has a particular purpose
What’s in a tablet?
The active ingredient may be very small but it may be difficult to take into the body. Added to a filler that bulks up the product to sensible size and a lubricant is added so tablets can be taken easily
Chromatography
Water separated dyes as it rises up the chromatography paper
Stationary phases
When the solvent didn’t move
Mobile phase
When water and dyes moved
Rf values
Distance moved by substance/distance moved by solvent
This is the ratio moved by a compound (from the origin to the centre of the spot) to the distance moved by the solvent
Assessing purity of drugs
Impure substances will separate
Pure substance will stay the same
RP: investigate how paper chromatography can be used in forensic science to identify an ink mixture used in forgery
Draw pencil line on litmus paper, put spots of different solvent on the line. Once solvent dry place paper in water below the pencil line and wait for them to separate
Once separate let paper dry then work out the Rf value
Hydrogen test
Squeaky pop
Oxygen test
Relighting a glowing splint
Carbon dioxide test
Limewater turns from colourless to milky white when carbon dioxide is bubbled through it
Chlorine test
Damp litmus paper is bleached
Producing flame colours
Wear goggles Clean wire with HCl and hold in blue flame Moisten a flame test wire with HCl Dip wire into sample solid chemical Hold flame test wire in blue flame Record colour of flame
Flame colours
Lithium Crimson Calcium orange red Sodium yellow Copper green Potassium lilac
Identifying substances
Flame tests can be used to identify cations in compounds
Coloured precipitates
A compound which contains a transition metal is often coloured
If sodium hydroxide solution is added to these precipitates form different colours
White precipitates
Sodium hydroxide solution also forms precipitates with other metal ions such as magnesium, calcium and aluminium
Reactions of carbonates
White carbonates if from group 1 or 2
Form colour carbonates if transition metal
React with acids to form CO2 which turns limewater milky
Testing for Halides
Test d using silver nitrate
