Chemical Analysis
combined science
- Created by: abbienoice
- Created on: 16-11-20 15:15
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- Chemical Analysis
- paper chromatography
- mobile phase
- where the molecules can move - always a liquid or gas
- stationary phase
- where the molecules cant move - solid or really thick liquid
- an analytical method used to separate and identify the substances in a mixture
- during the experiment the substances constantly move between the mobile and stationary phases - an equilibrium is formed between the phases
- the mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it
- how quickly a chemical moves depends on how its distributed between the two phases
- the chemicals that spend more time in the mobile phase than the stationary phase will move further through the stationary phase
- the components in a mixture will normally separate through the stationary phase, so long as all the components spend different amounts of time in the mobile phase
- the number of spots may change in different solvents as the distribution of the chemical will change depending on the solvent
- a pure substance will only ever form one spot in any solvent as there is only one substance in the sample
- in paper chromatography the stationary phase is the chromatography paper and the mobile phase is the solvent
- molecules with a higher solubility in the solvent and that are less attracted to the paper will spend more time in the mobile phase - carried further up the paper
- mobile phase
- purity
- a pure substance is something that only contains one compound or element throughout - not mixed with anything
- a chemically pure substance will melt or boil at a specific temperature
- you can tell the purity of a sample by measuring its melting or boiling point and comparing it with a pure substance
- the closer your measured value is to the actual melting or boiling point, the purer your sample is
- impurities in your sample will lower the melting point and increase the melting range of your substance
- impurities will increase the boiling point and may result in your sample boiling at a range of temperatures
- formulations
- formulations are useful mixtures with a precise purpose that are made by following a formula
- each component in a formulation is present in a measured quantity and contributes to the properties of the formula so that it meets its required function
- really important in the pharmaceutical industry
- can be found in cleaning products, fuels, cosmetics, fertilisers, metal alloys and food and drink
- chromatography analysis
- the result of chromatography analysis is called a chromatogram
- an Rf value
- Rf = distance travelled by substance(B) / distance travelled by solvent(A)
- the further through the stationary phase a substance moves the larger the R value
- paper chromatography
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