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chemistry > Separation Techniques > Flashcards

Separation Techniques Flashcards

1
Q

define a pure substance

A

a single substance that is not mixed with anything else

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2
Q

what is obtained in filtration

A
  • insoluble solid

- liquid

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3
Q

what is filtration used for?

A

to separate an insoluble solid from a liquid

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4
Q

what is the solid collected is the filtration paper called?

A

residue

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5
Q

what is the liquid passing through the filter paper called?

A

filtrate

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6
Q

what can filtration be used for?

A

can be used to purify drinking water at home and at water purification plants

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7
Q

what is an example of the usage of filtration?

A

sand and water

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8
Q

what is obtained in crystallisation?

A

soluble solid from a liquid

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9
Q

what is crystallisation used for?

A

it separates a dissolved solid from a solution to well-formed crystals

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10
Q

what can crystallisation be used for?

A

can be used to obtain pure sugar

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11
Q

what is the substance that dissolves called?

A

solute

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12
Q

what is the substance used to dissolve the solute called?

A

solvent

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13
Q

what is the end product called?

A

solution

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14
Q

what are the steps involving crystallisation?

A

1) the impure solid is dissolved in a solvent
2) the solution is heated to evaporate most of the solvent
3) the hot solution is allowed to cool. the solid appears as pure crystals
4) the cold solution is poured off to obtain the crystals. the crystals may be dried by pressing them between sheets of filter paper

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15
Q

what is example of crystallisation being used?

A

magnesium nitrate extracted from magnesium nitrate solution

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16
Q

what is obtained in evaporation to dryness?

A

soluble solid from a liquid

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17
Q

what is evaporation to dryness used for?

A

to obtain sodium chloride

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18
Q

how is evaporation to dryness used?

A
  • same way of obtaining crystals as crystallisation
  • but instead of heating the solution to half of its volume to make it more saturated, we heat it all the way until there is no more water left
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19
Q

what is an example of evaporation to dryness?

A

sodium chloride extracted from sodium chloride solution

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20
Q

what is obtained in simple distillation?

A

liquid from a soluble solid

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21
Q

what is simple distillation used for?

A

separates a pure liquid from a solution

22
Q

how does simple distillation work?

A

vapour condenses to a pure liquid which is called a distillate

23
Q

what is an example of simple distillation?

A

distillation of seawater to obtain pure water (desalination)

24
Q

what does desalination mean?

A

to remove salt

25
Q

what is obtained in fractional distillation?

A

miscible/soluble liquids

26
Q

what is fractional distillation used for?

A

separates mixtures of miscible liquids with widely differing boiling points

27
Q

what are miscible liquids?

A

liquids that are completely soluble with each other

28
Q

what is an example of fractional distillation?

A

fractional distillation of ethanol and water

29
Q

how and why does ethanol distill faster than water?

A

ethanol has a lower boiling point than water (78 degrees celsius) so it will distill first

30
Q

what are the three uses of fractional distillation?

A
  • to separate pure oxygen and pure nitrogen from liquid air
  • to separate substances in petroleum into fractions
  • to produce alcoholic drinks
31
Q

what is the use of the thermometer?

A
  • to determine the purity of the distillate
  • if thermometer shows a constant reading, distillate is pure
  • if thermometer shows a range of readings, distillate is impure
32
Q

what is the use of boiling chips?

A

to ensure smooth boiling

33
Q

what is the use of glass beads/shelves?

A

to increase surface area for repeated condensation and evaporation so that the distillate is as pure as possible

34
Q

what is obtained in using a separating funnel?

A

immiscible liquids

35
Q

what is the separating funnel used for?

A

to separate immiscible liquids from each other

36
Q

what are immiscible liquids?

A

liquids which are not completely soluble with each other

37
Q

what is an example of using a separating funnel?

A

oil and water

38
Q

what is obtained i paper chromatography?

A

mixtures of dyes, inks, urine etc

39
Q

what is paper chromatography used for?

A

separates and identifies mixtures

40
Q

what is an advantage of using paper chromatography?

A

only a small amount of mixture is needed

41
Q

what are the uses of paper chromatography?

A
  • to separate and identify mixtures of coloured substances found in food and dyes
  • to separate substances found in drugs, urine and blood
  • to find out if athletes have been using banned drugs to enhance their performance
  • to identify mixtures in colourless substances
42
Q

how is paper chromatography used to identify mixtures of colourless substances?

A
  • the chromatogram is sprayed with a location agent

- the locating agent reacts with the substances on the paper to produce a coloured product

43
Q

why is the start line drawn in pencil?

A

pen ink contains a mixture of dyes that may be dissolved by the solvent during the chromatography. these may travel up the chromatogram and complicate it

44
Q

why must the level of solvent be below the start line?

A

so that the dyes will not dissolve straight into the beaker of solvent but travel up the chromatogram instead

45
Q

why must the drops to be tested be small?

A

so that the final chromatogram will not be messy and inaccurate

46
Q

what is a characteristic of a pure substance?

A

it has fixed melting and boiling points

47
Q

what does an impurity do?

A

it lowers the melting point and raises the boiling point

48
Q

what’s the difference between between a pure and impure substance’s melting point?

A
  • a pure substance melts at a fixed temperature

- an impure substance melts over a range of temperatures

49
Q

what’s the difference between a pure and impure substance’s boiling point?

A
  • a pure substance boils at a fixed temperature

- an impure substance boils over a range of temperatures

50
Q

what’s the difference between the chromatogram of a pure and impure substance?

A
  • a pure substance produces a single spot on the chromatography
  • an impure substance produces two or more spots. each extra spot is due to an impurity

chemistry (19 decks)

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