Chemical analysis- paper 2 Flashcards
How is Purity Defined Differently in Chemistry to Everyday?
1)substance nothing has been added to it, natural state
2)chemistry: only contains one compound or element throughout - not mixed
How do you use the Boiling or Melting Point To tell You How Pure a Substance Is? 5
1)chemically pure substance will melt or boil specific temperature.
2)test the purity its melting or boiling point and comparing melting or boiling point of the pure substance.
3) closer your measured value is to the actual melting or boiling point, the purer
4)Impurities sample will lower the melting point and increase the melting range of your substance.
5)Impurities sample increase boiling point result sample boiling range temperatures.
What are Formulations? 2
.useful mixtures precise purpose that are made by following a ‘formula’.
.Each component measured quantity, contributes to the properties
Why are formulations important and some more uses? 5
1)pharmaceutical industry. formulation of a pill, delivers drug correct area right concentration, shelf life
2)cleaning products, fuels, cosmetics, fertilisers
How do you check if a product is a formulation?
composition packaging. ratio each component.
1)What is Chromatography?
2)How would you compare substances?
1).separate the substances in a mixture To identify the substances.
2)certain substance is present mixture. pure sample of that substance alongside the unknown mixture
What are the two phases in chromatography?
.A mobile phase - molecules can move. liquid or a gas. (solvent)
.A stationary phase - molecules can’t move. solid or a really thick liquid. (filter paper)
What happens in chromatography in the phases? 2
1)substances constantly move between mobile stationary phases-equilibrium between phases.
2) anything dissolved in mobile phase moves with it.
How quickly a chemical moves depends on…? 2
1)distributed between two phases - time mobile or stationary phase.
2) spend more time mobile phase than stationary phase move further.
How does chromatography work to separate and how does a pure substance present? 3
1)components mixture separate through stationary phase, components spend different amounts time mobile phase.
2)number spots, distribution chemical changes depending on different solvents.
3)pure substance only form one spot any solvent one substance sample.
The amount of time the molecules spend in each phase depends on two things?
=How soluble they are in the solvent.
=How attracted they are to the paper.
What happens when a molecule has a higher solubility?
.higher solubility in solvent, less attracted to the paper more time in the mobile further up the paper.
What are the results of chromatography analysis is called?
chromatogram.
What is an Rf value?
Larger rf vaulve =?
.ratio between distance travelled by the dissolved substance (solute)
.distance travelled by the solvent.
.futher through stationary phase a substance moves=larger the Rf value.
How you can Calculate the RF Value for Each Chemical?
.
What is the RF value dependent on? 1
How to ensure correct RF value to find the missing compound? 2
1)dependent on the solvent - change the solvent RF value substance will change.
2)test both mixture and reference in a number of different solvents.
3)RF value of Reference compound matches the RF value of one of spots in mixture in all the solvents, compound is present mixture.
Tests for Anions:
Test for Halides IONS (Cl-, B-, I-)?
2 steps and 3 results
1)drops of dilute nitric acid- remove hydroxide + carbonate ion= false positive
2)drops of silver nitrate solution
What is the 2 step test for metal hydroxides testing for positive (metal) ions?
What is the colours and ions corresponding and the general formula? 6
1)add drops sodium hydroxide solution mystery compound
2)coloured insoluble hydroxide
