analytical techniques I Flashcards
define volumetric analysis
an analytical technique where the principal measurement is volume - used to analyse solutions
define gravimetric analysis
an analytical technique where the principal measurement is mass - use to analyse either solutions or solids
define spectroscomy
an analytical technique where the principal measurement is light (electromagnetic radiation) intensity.
involves spectra/absorbance or transmission of specific wavelengths - analyse solutions
define chromatography
an analytical or separation technique reliant on the movement of components at different speeds due to their physical properties - analyse or separate mixtures
define emission
occurs when excited electrons return to their ground states and radiate energy of fixed wavelengths - emission spectra has coloured lines on black b/ground
define absorption
molecules can absorb energy of specific wavelengths - if occurs in visible spectrum then substance = appears coloured. has dark lines on rainbow spectrum
define absorbance
the intensity of light remaining after some has been absorbed, compared with the intensity of light when none has been absorbed
define transmittance
a measurement of the proportion of light that has been transmitted through a substance, where 100% transmittance means that no energy has been absorbed
what is a spectrometer?
an instrument that measures the light emitted or absorbed by excited electrons or molecules
define wavelength
the distance between the same point on two successive waves
define frequency
the number of waves that pass a given point in one second - HZ
electromagnetic spectrum directions
red to violet = increasing frequency
red to violet = increasing energy
red = low energy and violet = high energy
violet to red = increasing wavelength
absorption of light - colour wheel
ROY
GVB
complementary colours - if absorbing one colour, observing the complement
absorption of light - reflect
something appears to be a particular colour b/c it absorbs the wavelengths of light that are not that colour - so the colour is the only one reflected and not absorbed, so appears as that colour eg red paint
absorption of light - transmit
something appears to be a certain colour bc it absorbs the non-colour wavelengths of light, but the actual colour light is not reflected or absorbed, but transmitted = go through eg. cellophane
what is a primary standard
a substance whose amount in moles can be calculated accurately from their mass is called a primary standard
what are the characteristics of a primary standard
-be readily obtainable in a pure form
-have a known chemical formula
-be easy to store (as solid or solution) without deteriorating or reacting with air
-have a high molar mass to minimise the effect of errors in weighing
-preferable be highly soluble and inexpensive
what is the dilution factor
final volume/initial volume
substance in conical flask?`
analyte
volume measured out by the pipette is called an aliquot
substance in burette?
other substance dispensed slowly into conical flask is titrant, and volume of solution delivered is the titre
equivalence point
the point during the titration when the solutions have reacted in exact mole ratios shown by the reaction equation
end point
observable point where indicator used in reaction changes colour so signal to stop titration
what should the burette and pipette be rinsed with?
with the acid or base being rinsed with
what should the volumetric and conical flask be rinsed with?
only with deionised water
what is a systematic error
it produces a constant bias in a measurement that cannot be eliminated by repeating the measurement eg. uncalibrated pipette
what is a random error
they follow no regular pattern - unpredictable variations
components of colorimetry
-a light source that produces light that is absorbed by the solution
-this is passed through a filter to select a particular wavelength
-a glass, plastic or quartz cuvette to hold the sample
-an electronic detector to measure the absorbance of the light that passes through the cell
