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Chemistry > Analytical Techniques > Flashcards

Analytical Techniques Flashcards

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1
Q

A volumetic flask is…

A

the apparatus used to make up a solution to an accurately known volume

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2
Q

A volumetric pipette is…

A

the apparatus used to dispense an accurately known volume (aliquot)

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3
Q

An aliquot is…

A

an accurately known volume of a solution

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4
Q

A burette is…

A

the apparatus used to deliver an accurately known but variable volume of solution
measurements are made to the nearest 0.05mL

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5
Q

A primary standard is…

A

a substance that can be prepared pure and dissoled in water to make a solution that has an accurately known concentration

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6
Q

A primary standard solution is…

A

a solution containing one solute, prepared by dissolving a known mass of that solute into a known volume of water
the concentration is known accurately

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7
Q

Volumetric analysis is…

A

a quantitative analysis technique using volume as the principal measurement

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8
Q

A titrant is…

A

the solution in the burette, dispensed into the conical flask

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9
Q

The analyte is…

A

the solution in the conical flask, which has a known volume

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10
Q

The titre is…

A

the volume of titrant dispensed into the conical flask during a titration
calculated to the nearest 0.05mL

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11
Q

Concordant titres are…

A

titres within a total range of 0.10mL during one titration experiment

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12
Q

The mean titre is…

A

the average of all concordant titres in a titration experiment
calculated to two decimal places

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13
Q

The dilution factor is…

A

the final volume divided by the inital volume, where water has been added to dilute the solution

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14
Q

An indicator is…

A

a substance that changes colour at or near the equivalence point, often due to a change in pH

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15
Q

The equivalence point occurs when…

A

the exact mole ratio of reactants has been added (according to the balanced chemical equation)
neither reactant is in excess

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16
Q

The end point occurs when…

A

observable experimental evidence shows that the equivalence point has been reached

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17
Q

A titration curve is…

A

a graph plotting pH against volume of titrant added

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18
Q

A mistake is…

A

an avoidable error that may cause the experimental result to be inaccurate
experimental results involving mistakes should always be rejected

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19
Q

A systematic error is…

A

an error introduced by the method or apparatus, that cannot be eliminated by repeating the experiment
cause inaccuracy in the same direction for each experiment

20
Q

A random error is…

A

an error that may cause the experimental result to be higher or lower than the true value
can be minimised by repeating the experiment and using a mean value

21
Q

The empirical formula is…

A

a formula showing the simplest whole-number ratio between the elements in a compound

22
Q

The molecular formula is…

A

a formula showing the exact number of atoms of each element in a molecule of that compound

23
Q

Gravimetric analysis is…

A

a quantitative analysis technique using mass as the principal measurement

24
Q

A precipitate is…

A

a solid formed in a reaction between two solutions

25
Q

Repeatedly heating and drying the precipitate to constant mass is important as…

A

it ensures all impurities are removed and no moisture/water remains

26
Q

Spectroscopy is…

A

an analytical technique where the principal measurement is light intensity (electromagnetic radiation)
involves spectra, or the absorbance/transmission of specifc wavelengths
most commonly used to analyse solutions

27
Q

Emission occurs when…

A

excited electrons return to their ground states and radiate energy or fixed wavelengths
coloured lines on a black background

28
Q

Absorption occurs when…

A

molecules absorb energy of a specific wavelength
absorption in the visible spectrum will cause the substance to appear coloured
reverse of emission spectra; dark lines on a rainbow spectra

29
Q

Absorbance is…

A

the intensity of light remaining after some has been absorbed, compared with the intensity of light when none has been absorbed

30
Q

Transmittance is…

A

a measurement of the proportion of light that has been transmitted through a substance, where 100% transmittance means that no energy has been absorbed

31
Q

A spectrometer is…

A

an instrument that measured the light emitted or absorbed by excited electrons/molecules
- colorimeter, atomic absorption spectrometer and UV-visibe spectrophotometer measure absorbance
- infrared spectrophotometer measures transmittance

32
Q

Wavelength is…

A

the distance between the same point on two successive waves

33
Q

Frequency is…

A

the number of waves that pass a given point per second
measured in Hertz (Hz)

34
Q

Colorimetry is…

A

a method of determining the concentration of the analyte by measuring the relative absorption of light (usually visible) compared to solutions containing known concentrations of that substance

35
Q

A cuvette is…

A

a cell used to hold the analyte in spectroscopuc analysis

36
Q

A calibration curve is…

A

a plot of the results of an experiment at a range of known concentrations, so that these cna be compared with an experiment using an unknown concentration within that range

37
Q

UV-visible spectrometry is…

A

a more sophisticated analysis technique than colorimetry, but using a similar principle
a monochromator is used to produce a single wavelength of light in the visible or UV spectrum and the absorbance of the analyte at that wavelength is measured

38
Q

Ionisation is when…

A

chemical species lose or gain electrons

39
Q

Dissociation is when…

A

a molecule separates into smaller particles, often called ‘fragmentation’ in analysis

40
Q

Chromatography is…

A

a technique used to separate substances in a mixture

41
Q

Chromatography is used for identifying…

A
  • drugs in blood
  • sugars in fruit juice
  • hydrocarbons in oil
  • pollutant gases in exhaust fumes
  • pesticides in water and soil
  • food dyes in sweets
  • pigments/dyes in ink
42
Q

Chromatography has two phases:

A
  • stationary phase: a solid or liquid the sample is applied to
    -> adsorbs to the stationary phase
  • mobile phase: a liquid or gaseous phase that is passed through/over the sample
    -> carried along by mobile phase
43
Q

Thin layer chromatography characteristics

A
  • stationary phase is plastic coated in Al2O3 or SiO2
  • enables use of solvents that damage paper
  • greater range of substances able to be separated
  • faster
44
Q

Retention factor represents…

A

the attraction/solubility in the mobile phase - higher Rf value = more attracted to mobile phase, lower Rf value = more attracted to stationary phase

45
Q

Retention factor equation is…

A

Rf = distance spot moved/distance solvent moved

Chemistry (4 decks)

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