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higher chemistry > 3.5 - chemical analysis > Flashcards

3.5 - chemical analysis Flashcards

1
Q

what is a standard solution?

A

a solution of accurately known concentration

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2
Q

what are the six steps required to make a standard solution?

A
  • calculate mass required for standard solution
  • measure out mass using a mass balance
  • transfer to beaker
  • dissolve in a minimal volume of deionised water
  • transfer to a volumetric flask with washings
  • make up to graduation mark with deionised water
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3
Q

what is volumetric analysis?

A

using a solution of accurately known concentration in a quantitive reaction to determine the concentration of an unknown

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4
Q

what is a pipette used for?

A

accurately measures volume of unknown solution

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5
Q

what is a pipette filler used for?

A

used to fill pipette

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6
Q

what is a burette used for?

A
  • dispenses measured volumes of a liquid
  • usually the standard solution which goes in the burette
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7
Q

what is a conical flask used for?

A
  • usually contains the unknown sample
  • narrow neck allows for swirling
  • used for mixing liquids
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8
Q

what is a white tile used for?

A

allows the end-point to be detected more accurately

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9
Q

what is the first titration described as and why?

A

rough as it only gives an idea of the volume of standard solution required

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10
Q

what are concordant results?

A

within 0.2cm3 of eachother

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11
Q

what are the two types of volumetric titrations?

A
  • acid-based titration: based on a neutralisation reaction, normally an indicator required
  • redox titration: where an oxidising and reducing agent react, an indicator is not always required, some reactions are described as self-indicating
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12
Q

why is deionised water used in a titration?

A

tap water may contain the ions in the standard solution which would affect the concentration of the solution

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13
Q

what is the colour change that takes place when permanganate is used?

A

colourless to purple

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14
Q

what are points of good practice when filling a burette?

A
  • rinse apparatus with solutions to be used to avoid contamination
  • ensure all air bubbles are removed to ensure accuracy of calibration
  • dry outside of burette once filled
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15
Q

what are good points of practice when carrying out a titration?

A
  • use white a tile below conical flask (to ensure an accurate end-point)
  • ass solution from burette drop-wise as end-point is approached
  • swirl flask to ensure mixing of solutions
  • always read burette scale at eye level (ensures accurate reading of burette)
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16
Q

what are four commonly used reagents in redox titrations?

A
  • iodine
  • permanganate
  • dichromate
  • chromate
17
Q

what is chromatography used to do?

A

used to separate and identify components of a mixture

18
Q

what are the three types of chromatography?

A
  • paper
  • thin-layer
  • gas-liquid
19
Q

what are the features of paper chromatography?

A
  • mobile phase: liquid
  • stationary phase: paper
20
Q

what are the features of thin-layer chromatography?

A
  • mobile phase: liquid
  • stationary phase: silica coated plate
21
Q

what are the features of gas-liquid chromatography?

A
  • mobile phase: gas
  • stationary phase: liquid
22
Q

what are the two factors that chromatography is based on?

A
  • polarity
  • molecular size
23
Q

which molecule would move up the paper further in a polar solvent?

A

polar molecule

24
Q

what happens during paper chromatography?

A
  • a small sample of mixture is placed near the bottom of the chromatography paper and thn the paper (stationary phase) is placed ina solvent (mobile phase)
  • the solvent moves up the paper
  • some components in the mixture will move up more rapidly with the solvent while others will take longer
  • the identity of a component can be indicated by the distance it has travelled in the solvent
25
Q

what is the formula for finding out the Rf value?

A

Rf = distance travelled by substance/distance travelled by solvent front

26
Q

what are two uses of chromatography?

A
  • follow the course of a chemical reaction
  • identify the products in a chemical reaction
27
Q

what is the stationary phase in gas-liquid chromatography?

A

a high boiling point liquid held on an inert powered support material

28
Q

what is the mobile phase in gas-liquid chromatography?

A

an inert gas e.g. helium or nitrogen

29
Q

what are the two factors which the rate of travel through the column during gas-liquid chromatography depend on?

A
  • the attraction (compatibility) between component molecules and the liquid held on the stationary phase
  • the size of the molecules
30
Q

what is retention time?

A

the time taken to move through the column

higher chemistry (11 decks)

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