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Analytical Techniques Flashcards

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
Repeatedly heating and drying the precipitate to constant mass is important as...
it ensures all impurities are removed and no moisture/water remains
26
Spectroscopy is...
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
Emission occurs when...
excited electrons return to their ground states and radiate energy or fixed wavelengths coloured lines on a black background
28
Absorption occurs when...
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
Absorbance is...
the intensity of light remaining after some has been absorbed, compared with the intensity of light when none has been absorbed
30
Transmittance is...
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
A spectrometer is...
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
Wavelength is...
the distance between the same point on two successive waves
33
Frequency is...
the number of waves that pass a given point per second measured in Hertz (Hz)
34
Colorimetry is...
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
A cuvette is...
a cell used to hold the analyte in spectroscopuc analysis
36
A calibration curve is...
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
UV-visible spectrometry is...
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
Ionisation is when...
chemical species lose or gain electrons
39
Dissociation is when...
a molecule separates into smaller particles, often called 'fragmentation' in analysis
40
Chromatography is...
a technique used to separate substances in a mixture
41
Chromatography is used for identifying...
- 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
Chromatography has two phases:
- 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
Thin layer chromatography characteristics
- 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
Retention factor represents...
the attraction/solubility in the mobile phase - higher Rf value = more attracted to mobile phase, lower Rf value = more attracted to stationary phase
45
Retention factor equation is...
Rf = distance spot moved/distance solvent moved

Chemistry (4 decks)

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