Chemical Analysis Flashcards
What is a pure substance?
Made up of just 1 substance (either an element or compound)
What are fixed points in an element or compound
Melting and boiling points
Pure substances, impurities and mixtures fixed points
Pure substances = have specific temperatures at which they melt and boil
Mixtures = do not have sharp melting and boiling points, state changes over range of temperatures
Impurities = lower the melting point and raise boiling point of substances, size of difference of pure substance is its fixed point. The purer the compound the narrower the melting point range
What is a formulation?
Mixture been designed to produce a useful product
Often contain between 5-10% of active drug, with specific compound that affects nobody to cure illness and relieve someone of their symptoms
Paint formulations
Pigment
Binder (to wall)
Solvent (spread)
Cleaning agents forumlations
Surfactant (removes grease)
Water (squirt easily)
Colouring and fragrance additives
Rinse
What does chromatography involve?
Mobile and stationary phase
Mobile = moves through stationary phase carrying components of mixture
Substance with stronger force of attraction to stationary phase will not travel as far
What does chromatography tell you?
If mixture if a single compound or mixture
More than one spot = mixture
Single spot = pure substance
How to find distance spot travels up paper?
Retention factor = distance moved by substance from base line / distance moves by solvent (from base line to top)
How to test for hydrogen
Lighted splint pops
Testing for oxygen gas
Glowing splint relights
Test for carbon dioxide
Limewater turns milky
Test for chlorine
Blue litmus paper turns white
Metal ion and flame colour
Lithium = crimson Sodium = yellow Potassium = lilac Calcium = orange-red Copper = green Magnesium = no colour
How to carry out a flame test
1) Nichrome wire loop dipped in concentrated hydrochloride acid
2) Dipped in acid again before dipping it into metal compound being tested
3) Hold loop in flame of Bunsen Burner
4) Colour identifies metal ion
5) If its a mixture of metal ions, dominant colours can show
Metal cation tests with sodium hydroxide
Identify positive ions
Aluminium, calcium and magnesium form white precipitates with sodium hydroxide solution
Ions will not dissolve
Test for carbonate equation
CO2 + 2H -> CO2 + H2O
Colour of precipitate telling you which halide ion is present
Iodide = yellow Bromide = cream Chloride = white
How to test halides
Add dilute nitric acid and silver nitrate solution
If a precipitate forms then a halide is present
Benefits and disadvantages of instrumental methods
Highly accurate
Quicker
Very small samples
Expensive
Training needed
Interpreted only by comparison with date from known substances
What are instrumental methods important for?
Important in work of environmental agencies fighting pollution
What do chemists use flame emission spectroscopy for?
Analyse samples for metal ions
How is flame emission spectroscopy done?
Sample is heated in flame
Energy provided makes electrons in metal ions jump into higher shells
Fall back into lower shells and their energy is released as light
How are wavelengths analysed?
Analysed by passing it through a spectrum
Each metal ion absorbs and gives out its own light spectrum
Light spectrum can be compared
