CHEMICAL ANLYSIS

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PURITY

A pure substance is something that contains only one compound or element throughout it is not mixed with anything else

a chemically pure substance will melt or boil at a specific temperature

you can test the purity of a sample by measuring its melting or boiling point and comparing it with the melting or boiling point of the pure substance

the closer your measured value is to the pure substance the purer it is

impurities in your sample:

lower the melting point and increase the melting range of your substance

increase the boiling point and may result in your sample boiling at a range of temperatures

FORMULATION

useful mixtures with a precise purpose that are made by a following formula

each component present is in a measured quantity and contributes to the properties of the formulation so that it meets its required function

Paint:

pigment- gives the paint colour

solvent- used to dissolve the other components and alter the viscosity

binder- forms a film that holds the pigment in place after it has been painted on

additives- added to further change the physical and chemical properties of the paint

important in pharmaceutical industry e.g by changing the formulation of a pill:

chemists can make sure it delivers the drug to the correct part of the body at the right concentration

that its consumable

has a long shell life

when buying a product you may find a percentage or ratio for each of the component--> formulation

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PAPER CHROMATOGRAPHY

used to separate the substances in a mixture to identify the substances

mobile phase: where the molecules can move. This is always a liquid or gas

stationary phase: where the molecules can't move. This can be a solid or a really thick liquid

substances in the sample move between the phases- an equilibrium is formed between the two phases

the mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it

chemicals moving quickly: depends on how it is distributed between the two phases( whether it spend more time in which phase)

mobile phase: chemicals that spend more time here will move further through the stationary phase

components will usually separate through the stationary phase as long as the different components send different amount of time in the mobile phase

number of spots may change in different solvents as the distribution of the chemical will change depending on the solvent

pure substance: forms only 1 spot in any solvent as there is only one substance in the sample

paper chromatography:

stationary phase: chromatography paper

the more soluble a colouring is the further up the page it will travel

mobile phase: solvent

amount of time the molecules spend i each phase depends on:

how soluble hey are in the solvent

how attracted they are to the paper

molecules with higher solubility in the solvent and which are less attracted to the paper will spend more time in the mobile phase and they will be carried further up the paper

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CONTINUING PAPER CHROMATOGRAPHY

Rf value: ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent

the further the through the stationary phase a substance moves, the larger the Rf value

result of chromatography: chromatogram

it is often carried out to see it a certain substance is present in a mixture--> you can un a pure sample of that substance alongside the unknown mixtures

Rf value is dependant on the solvent- if you change the solvent the Rf value will change