Analysis of Chemistry Flashcards
What is quantitative and qualitative analysis?
Quantitative is based on numerical data,
Qualitative is based on information and description.
In chromatography how are substances separated?
They are separated by the movement of a mobile phase through a stationary phase
What are aqueous and non-aqueous solutions?
An aqueous solution is a solution that contains substances dissolved in water,
A non-aqueous solution is a solution that contains substance dissolved in other solvents
What does immiscible mean?
It means two solvents will not mix, instead they will form separate layers
What does the separation by chromatography depend on?
It depends on the distribution of the solvent in the sample between the mobile and stationary phase.
The more soluble substance will move more when the mobile phase moves, the less soluble will stay attached to the stationary phase
What does soluble mean?
How soluble something is is the amount a solute (solid) dissolves in a solvent (liquid)
Whats the difference between paper and thin-layer chromatography?
In paper chromatography the stationary phase is a piece of chromatography paper, whereas in thin-layer chromatography, the stationary phase is a plate of plastic or glass covered in a solid like silica
What is the formula for finding the Rf values for a substance?
(distance moved by sample)/ (distance moved by solvent)
How can we use the Rf values obtained from a chromatography test?
The Rf value for a substance is always the same in the same conditions, therefore we can compare the Rf value from the test to known substances to determine if they’re the same
What is a locating agent?
Some substances are not coloured and so to see how far they’ve travelled, a locating agent is added so the spots can be seen
In gas chromatography what is the stationary and mobile phase?
The stationary phase is a long metal tube, often coiled to save space,
The mobile phase is an inert gas that is the ‘carrier gas’ that takes the test substance along the metal tube
How are the results of gas chromatography found and collected?
The metal tube that the gas passes along is heated, this means that some substances will be attracted to the tube, and some more than others. Therefore some gases travel through the tube faster and then the gases that come out the tube first are recorded.
What do the axis on a gas chromatogram show?
The time it takes for each substance to travel along the tube is recorded and is the retention time, this separates the substances. Each substance will have a different height or peak, this indicates how much of each substance is in the mixture
What are the main stages of a quantitative analysis?
a. measuring out accurately a specific mass or volume of the sample
b. working with replicate samples
c. dissolving the samples quantitatively
d. measuring a property of the solution quantitatively
e. calculating a value from the measurements
f. estimating the degree of uncertainty in the results
What is the concentration of a solution measured in?
g/dm^3
