Flashcards
paper chromatography
Cards in this deck (9)
- 1what is chromatography?chromatography is used to separate mixtures of soluble substances. These are often coloured substances such as food colourings, inks, dyes or plant pigments.
- 2what are the two phases of chromatography?-stationary phase
-mobile phase
The different dissolved substances in a mixture are attracted to the two phases in different proportions. This causes them to move at different rates through the paper. - 3what is the mobile phase?the mobile phase is the solvent that moves through the paper, carrying different substances with it
molecules can move. this is always a liquid or a gas - 4what is the stationary phase?the stationary phase, which in paper chromatography is very uniform, absorbent paper
molecules can't move. can be solid or thick liquid - 5paper chromatography step by step- draw a pencil line near bottom of paper. this is the baseline
-put spot of mixtures to be separated on to the line
-put some solvent into a beaker
-As the paper is lowered into the solvent, some of the dye spreads up the paper
-The paper has absorbed the solvent, and the dye has spread further up the paper - 6how do you identify pure substances on a chromatogram?a pure substance produces one spot on the chromatogram
- 7how do you identify impure substances on a chromatogram?an impure substance produces two or more spots
- 8how do you identify identical substances on a chromatogram?A paper chromatogram can also be used to identify substances by comparing them with known substances. Two substances are likely to be the same if:
-they produce the same number of spots, and these match in colour
-the spots travel the same distance up the paper (have the same Rf value) - 9calculate Rf valuesRf= distance travelled by SOLUTE / distance travelled by SOLVENT
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- Year 11 Chemistry (Unit 1) Flashcards on paper chromatography , created by Melissa Anoble on 21/04/2018.
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- Melissa Anoble
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