Chemistry- chromotography
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24 Terms
where do you put the start line on your chromatograph?
where the samples are placed- this start line is drawn in pencil
Why is the start line drawn in pencil?
because it is insoluble and does not disolve in the solvent
What is a solvent
a liquid which a solvent dissolves
What is the stationary phase
The chromotography or filter paper
what is paper chromatography used for?
separating different dyes in an ink
What is the solvent front?
The highest point the solvent has reached
What do we think the phases as when explaining chromatography?
We don't want to think of these phases as periods of time but types of substances
What is the stationary phase?
A substance or material that the molecules can’t move in
what is the mobile phase in chromatography
the substance that the molecules can move in
Why do different chemicals move up the filter paper at different rates?
different chemicals in our sample will constantly change between the mobile and stationary phases. How much time they spend on the phases, determines how fast they move up the paper.
Which stage do chemicals which are less soluble stay in longer?
stationary phase
how do we calculate the rf value?
Distance travelled by the substance / Distance travelled by the solvent
What is the mobile phase in paper chromatography?
the solvent
what does the Rf value tell you about the solubility of a separated component
a larger value tells us that the component is more soluble in the solvent
if a substance did not move from the start line, what is it?
insoluble
what is the stationary phase in paper chromatography
the paper
Which is pure?
2
which is insoluble
1
which is impure
3, 4, 5
what is the Rf value used to identify?
uknown substnaces within a mixture
how and when do we use the Rf value?
to identify unknown compounds
what is a key factor of the Rf value?
it is always below 1
what is chromotography?
a technique that separates small amounts of dissolved substances by running a solvent along absorbent paper