Purity, formulations and chromatography Flashcards
What is a pure substance?
A single element or compound not mixed with any other substance.
How can you tell the difference between a pure substance and a mixture?
Pure substances have fixed melting & boiling points. Mixtures melt and boil within a range of melting and boiling points.
What can a “pure substance” mean in everyday language?
A substance that has had nothing added to it, so it is unadulterated and in its natural state, e.g. pure milk or pure orange juice.
What is formulation?
A mixture that has been designed as a useful product
How is formulation made?
A formulation is made by mixing specific quantities of different substances to make something useful.
Give 7 examples of a formulation.
Fuels, cleaning products, paints, medicines, alloys, fertilisers and foods.
How is chromatography useful?
It can be used to separate mixtures and can give information to help identify substances
How are mixtures separated by chromatography?
Chromatography involves a stationary phase (e.g. paper) and a mobile phase (e.g. solvent). Separation depends on the relative attraction between the stationary phase and the mobile phase
What is the Rf value of a compound?
The ratio of the distance moved by the substance to the distance moved by the solvent.
What is the equation for calculating the Rf value of a compound?
Rf = distance moved by the substance ÷ distance moved by the solvent
How can Rf values be used to identify different compounds?
Different compounds have different Rf values in different solvents.
How can chromatography be used to distinguish pure substances from impure substances or mixtures?
The substances in a mixture may separate into different spots depending on the solvent but a pure substance will produce a single spot in all solvents.
