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IP Secondary 3 Chemistry > (Revision) Purification & Separation > Flashcards

(Revision) Purification & Separation Flashcards

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1
Q

Appropriate apparatus for measurement of time (2)

A

stopwatch (analog and digital), stopclock

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2
Q

Appropriate apparatus for measurement of temperature (1)

A

thermometer

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3
Q

Appropriate apparatus for measurement of mass (2)

A

beam balance, electronic balance

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4
Q

Appropriate apparatus for measurement of volume (4)

A

beaker, measuring cylinder, burette, pipette

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5
Q

The beaker is used to ________ the volume

A

estimate

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6
Q

The measuring cylinder is more ________ than the beaker

A

accurate

accuracy = 1cm3

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7
Q

The burette measures volume with an accuracy of ______

A

0.1cm3

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8
Q

The pipette measures ________ (i.e. ___cm3, ___cm3, ___cm3)

A

fixed volumes
10
20.0
25.0

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9
Q

Melting point of pure substances

A

Fixed melting point

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10
Q

Melting point of impure substances

A

Melting takes place over a range of temperatures

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11
Q

How are melting points of impure substances changed?

A

Impurities will LOWER the melting point. The greater the amount of impurities, the lower the melting point of the substance

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12
Q

Boiling point of pure substances

A

Fixed boiling point

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13
Q

Boiling point of impure substances

A

Boiling takes place over a range of temperatures

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14
Q

How are boiling points of impure substances changed?

A

Impurities will INCREASE the boiling point. The greater the amount of impurities, the higher the boiling point of the substance

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15
Q

If chromatography is conducted on a pure substance, …

A

One single spot seen on the chromatogram

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16
Q

If chromatography is conducted on an impure substance, …

A

Two or more spots seen on the chromatogram

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17
Q

When the pressure increases, the melting point ________

A

increases

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18
Q

When the pressure increases, the boiling point ________

A

increases

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19
Q

When the pressure increases, the melting point of water ________.

A

decreases

20
Q

What are miscible liquids?

A

Liquids that mix together completely to form a solution

21
Q

What are immiscible liquids?

A

Liquids that do not dissolve in each other

22
Q

Filtration is used to ________

A

separate a mixture of an insoluble solid and a liquid

23
Q

What is the residue?

A

The solid that remains on the filter paper

24
Q

What is the filtrate?

A

The liquid that passes through the filter paper

25
Q

Crystallisation is used to ________

A

recover soluble solid from a liquid

26
Q

Crystallisation (method)

A
  1. Solution is heated until saturated
  2. Solution is cooled until crystals form
  3. Crystals are dried between filter paper.
27
Q

What is a saturated solution?

A

The solution contains as much solute as can be dissolved at a particular temperature

28
Q

Crystallisation is suitable for substances

  • whose solubility ________
  • that will ________ on heating
A

differs appreciably with temperature

decompose

29
Q

Evaporation to dryness is used to ________

A

recover soluble solid from a liquid

30
Q

Evaporation to dryness is suitable for substances

  • whose solubility ________
  • that will ________ on heating
A

does not change much with temperature

NOT decompose

31
Q

Separation funnel is used to ________

A

separate immiscible liquids

32
Q

Separation funnel (method)

A
  1. Mixture is poured into the funnel and the layers are allowed to separate out
  2. The lower and denser layer is run off by opening the tap and is collected first
33
Q

Simple distillation is used to ________

A

recover a liquid from a soluble solid-liquid mixture

34
Q

Simple distillation (method)

A
  1. Solution boils, water vapourises and enters the condenser
  2. Water vapour is cooled in the condenser and changes back into pure water which is collected in the beaker.
  3. The solution becomes more concentrated and eventually becomes the solute.
35
Q

Fractional distillation is used to ________

A

separate miscible liquid-liquid mixture whose boiling points differ less than 25°C

36
Q

Fractional distillation (method)

A
  1. Solution boils, solution vapourises and enters the condenser.
  2. The liquid with the lower boiling point will become vapour and rise up. The liquid with the higher boiling point will condense in the fractionating column and fall back to the distillation flask.
  3. When all the liquid with the lower boiling point condenses and collected, the temperature will rise quickly and allow the other liquid to condense and be collected next.
37
Q

Function of boiling chips

A

To smoothen boiling and prevent bubbling

38
Q

Function of thermometer

A

To measure the temperature of the vapour as it leaves the distilling flask

39
Q

Positioning and function of condenser

A
  • Should be slanted to allow the gas to touch the walls of the condenser easily and transfer heat to the cold water, allowing the vapour to cool down
  • Cold running water should also be allowed to run from the bottom of the condenser and leave from the top (ensures that the entire water jacket is constantly filled with water)
40
Q

Chromatography is used to ________

A

to separate and identify small amounts of substances that are dissolved in solvents

41
Q

Principle of chromatography

A

Substances are separated because of differences in solubilities in a particular solvent

42
Q

________ substances travel further and faster

A

More soluble

43
Q

Rf value

A

Distance travelled by the substance / Distance travelled by the solvent

44
Q

Precautions when conducting chromatography

A
  1. Starting line should be drawn with a pencil.
    (ink will dissolve in the solvent together with the dyes)
  2. Spots of solution and dyes on the starting line should be small and concentrated
    (ensures that the dyes are clearly separated in distinct lines)
  3. Solvent line should be near the top of the paper
    (ensure that the dyes are fully separated)
45
Q

For colourless substances, the chromatogram may be sprayed with a ________ to show the location of the substances

A

locating agent

IP Secondary 3 Chemistry (9 decks)

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