C10 Flashcards
(31 cards)
Purity
A pure substance is one that is made up of just one substance. That substance can be either an element or compound
What is purity not?
-Its not referring to chemical purity
-e.g. orange juice advertised as pure
What are the fixed points of an element or compound?
The melting and boiling points
Use of melting and boiling points:
-to identify pure substances
Test for purity of water:
-is that its melting point is 0 degrees and its boiling point is exactly 100 degrees
Melting and boiling points of an impure substance:
Impurities tend to lower the melting points of a substance and raise the boiling points
Melting point of purified sample of caffeine:
234-237 degrees
Melting point of impure sample of caffeine:
180-220 degrees
What is a formulation?
A mixture that has been made of definite proportions, designed to give a product the best properties to carry out a function
Examples of formulations:
Fuels, alloys, fertilisers, cosmetics, food products
Formulations in tablet form:
Aid their dissolving at the most effective place in the digestive tract
What do paints contain:
-pigment, to provide colour
-a binder, to help paint attach
-a solvent, help pigment spread
What do washing up liquids contain?
-a surfactant, to remove the grease
-water, to thin out the mixture so it squirts easily
-colouring and fragrance addictives
-rinse agent, to help water drain off
What might chromotography be used for?
To seperate and identify mixtures of amino acids
Amino acids
They are colourless but appear as purple spots on paper when sprayed with a locating agent and dried
Rquired practical for paper chromotography?
Seperate dyes in inks or food colourings
What does chromotography always involve?
Mobile phase and stationary phase
Process of chromotography:
-The mobile phase moves through the stationary phase
-each component in the mixture will have a different attraction for the mobile phase and stationary phase
-substance with stronger attraction to mobile phase will travel a greater distance in a given time
-substance with stronger attraction to stationary phase will travel less
What is the mobile phase in paper chromotography?
The solvent
What is the stationary phase in paper chromotography?
The paper
What will the results be if the unknown sample is a mixture of compounds?
There will be more than one spot formed
What does a single spot suggest?
Its a pure substance
Rf (retention factor) equation
Distance moved by substance/distance moved by solvent
Rf values:
Can be measured and matched against databases to identify substances