8 Analysis Flashcards
What is chemical analysis?
The process of establishing what chemicals are present in a substance
In everyday language what is a “pure” substance?
A substance that has had nothing added to it and is in its “natural” state
In chemistry what is a “pure” substance?
A substance made of a single element or compound
How can pure substances be distinguished from impure ones?
By their melting/boiling points
Describe the melting and boiling points of pure substances
One very specific temperature
Describe the melting and boiling points of impure substances
They change state at a range of temperatures
What is a formulation?
A complex mixture designed as a useful product
Give three examples of formulations
Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.
What is chromatography?
A process to separate the constituents of a mixture
In paper chromatography, what is the stationary phase and what is the mobile phase
Paper is stationary, solvent (usually water or ethanol) is mobile
How can chromatography show the difference between pure and impure substances?
Pure ones will not separate into a number of spots
How is the Rf value calculated?
distance moved by spot/distance moved by solvent
What does a substance’s Rf value depend on?
How soluble it is in the solvent
In chromatography, why must the substances be placed on a pencil line?
Pencil will not dissolve in the solvent
In chromatography why must the solvent height be lower than the pencil line?
So that the substances do not dissolve into the solvent off the paper
