C2.1 Flashcards
What is relative atomic mass?
The mean mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom
If there are atoms in a bracket with a subscript number next to it, what does that mean?
Every atom in that bracket should be multiplied by that number
What is relative formula mass?
The mean mass of a unit of a substance compared to 1/12 the mass of a carbon 12 atom
What is the rfm of water?
18
What is empirical formula?
The simplest whole number ratio of atoms in each element
How can you use rfm to balance equations?
The total rfm on both sides of the equation can be altered and checked to be equal
What is chemical purity?
When a substance only has one sort of thing or atom in it
What is an example of a useful mixture?
Water
Alloys
A lot of stuff
How can you determine whether a solid substance is pure with a bunsen burner?
Heat it up, and if it is pure then it will stay at the same temperature while melting but if it is impure it melts over a range of temperatures
Pure Substance X melts at 500 degrees celcius
Pure Substance Y melts at 450 degrees celcius
If impure substance Z melts at 510 degrees celcius,what conclusions could you make about it?
It is neither X nor Y, impure substances never melt higher than the pure version
How does filtration work?
It separates an insoluble substance from a solvent,as the solvent can pass through microscopic holes in the filter paper
What is the remains of filtration called
Residue
How does crystallisation work?
You heat a solution slowly,so that the solute gets left behind in regularly shaped crystals
You can filter them and dry them in an oven
How does simple distillation work?
If the solvent has a lower boiling point,you can heat it up so it evaporates,then passes through a condenser where cold water condenses it and you get pure solvent.
How does fractional distillation work?
It separates 2 or more substances from a mixture in liquid state.
It has a fractionating column
Where vapours condense and heat it up
This means that 2 gases will be separated as one condenses
Why would you heat ethanol electrically?
Ethanol is flammable so a naked flame could cause fire
How does chromatography work?
It separates a mixture into its different substances
It relies on a stationary phase and mobile phase
The distance a spot travels depends on how well it bonds with each phase
What is the stationary and mobile phase in paper chromatography?
Absorbent paper
Water (most likely)
What is the stationary and mobile phase in thin layer chromatography?
Silica or alumina powder on a glass/plastic plate (tlc plate)
A solvent,probably not water
What is the stationary and mobile phase in gas chromatography?
Silica or alumina powder packed in a metal column
Unreactive carrier gas
How do you work out retention factor?
Distance travelled by substance / distance travelled by solvent
No units
How does a chromatogram show a substance?
A peak in the graph
What things do you need to be careful about when doing paper chromatography?
Draw the line in pencil
Draw the line and dot above the solvent
Keep the paper in place
If a spot in chromatography doesnt move,what does it suggest?
It is insoluble in the used solvent
How can you tell if food has a certain food colouring?
Do chromatography and if the 2 have a spot of the same Rf then the food has that colouring
How do you separate crude oil?
By fractional distillation
What 2 methods can you use to separate Salt and sand from water
First filtration
Then crystallisation
