chemical analysis

Question 1

a pure substance =

Answer 1

single element or compound, not mixed with any other substance and has a fixed melting and boiling point

Question 2

formulations

Answer 2

complex mixtures that have been designed as a useful product

Question 3

what is chromatography?

Answer 3

a seperation technique that can seperate substances based on their solubility

Question 4

the paper is the ______ phase because ______

Answer 4

stationary

it does not move

Question 5

the solvent is the _____ phase because _______

Answer 5

mobile

it does move

Question 6

in chromatography, a pure compound will…

Answer 6

produce a single spot in all solvents

Question 7

in chromatography, a mixture will…

Answer 7

have its compounds seperate into different spots depending on the solvent

Question 8

a more soluble substance….

Answer 8

travels further up the paper than a susbtance which is less soluble

Question 9

using chromatography to identify an unknown substance

Answer 9

• measure from pencil line to center of spot
• measure the distance moved by the solvent
• then calculate the Rf value
• this can be looked up in a database
• the experiment may need to be repeated with different solvents because several substances have the same Rf value
• the susbtance may have also never been analysed, so we would have to repeat further

Question 10

Rf value formula

Answer 10

distance moved by substance / distance moved by solvent