Topic C8 - Chemical Analysis Flashcards
What is PURE SUBSTANCE chemical definition?
A substance containing only one element or compound.
What is PURE SUBSTANCE everyday definition?
A substance with nothing added to it, e.g milk
What two things will a chemically pure substance do?
1) Melt at a specific temperature
2) Boil at a specific temperature
How can you test the purity of a sample?
By comparimg its melting or boiling point with that of the pure substance.
What 2 things will impurities in a sample do?
1) lower the melting point and increase the melting range
2) increase the boiling point and may also increase the boiling range
Formulations definition?
Useful mixtures with a precise purpose.
Examples of FORMULATIONS
1) metal alloys
2) medicines
3) fertilisers
4) paints
5) food
6) fuels
7) cosmetics
8) cleaning products
Chromotography defintition
An analytical method used to seperate the substances in a mixture. It can be used to identify the substances.
What is the CHROMOTOGRAPHY STATIONARY PHASE?
Where the molecules can’t move.
e.g chromotography paper
How can you tell if a substance is pure using CHROMOTOGRAPHY?
A pure substance will only ever form one spot in any solvent.
What is the CHROMOTOGRAPHY MOBILE PHASE?
Where the molecules can move
(the solvent)
e.g water or ethanol
What does CHROMOTOGRSPHY show?
How pure or impure a substance is
What is the CHROMOTOGRAPHY pathway?
1) Substances dissolve in the mobile phase
2) The mobile phase moves through the stationary phase
3) Substances that are more soluble or less attracted to the stationary phase move further
What is Rf value?
The ratio between the distanced travelled by the dissolved substance, and the distance travelled by the solvent.
Rf value formula
Distance travelled by substance
Rf = ——————————-——————
Distance travelled by solvent
