Topic 11; Measurement + data processing

resut in a different between recorded value and generally accepted value

caused by; • readiability of measuring instrument • effects of change sin surrounds (temperature or ai currents) • insufficient data • observe misinterpreting reading • errors can be reduced by repeated measurement; imporatnt to have repetable and reproducible experiments example; experimenter approximating reading

• as a result of poor experimental deisgn or procedure • can NOT be reduced by repeating experiment examples; • measuring volume of water form top rather than bottom of meniscus • overshooting volume of a liquid delivered in a titration • useing an acid-base indicitator that doesn’t correspond to the equivalence point of the titration • heat loss in exothermic reaction

• the smaller the systematic error; the great the accuracy • small systematic errors • give a result close to accepted value

• the smaller the random uncertainties, the greater the precision • small random errors • reproducible in repeated trials • repeated measurements are all in a close value to one another

absolute uncertainty/measured value x 100

accepted value- experimental value/accepted value x 100

• whenever you manipulate data, answer should be quoted to the same number of significant figures as the least precise value

• qualitive analysis • quantitve analysis • structural analysis

detection of presences but not quantity

detection of quantity of substance describption of molecular arragnement

used to determine the relative atomic and molecular masses - use fragmentation patterns as fingerprint techniques to identify unknown substances/molecular arrangement

(parent ion) is formed when a molecule loses one electron but remains otherwise unchanged; parent ions can break into smaller ions in mass spectrometer (causing fragmentation pattern)

• electron gun hits incident species and removes electron • collision energetic; splits molecule into fragments; largest peak in mass spectrum correspond to parent ion which didn’t get fragmented • fragmentation pattern can provide evidence for structure of compound

index of hydrogen deficiency; provides a measure of the structure of a molecule once its formula is known -measure of how many hydrogen molecules would be needed in theory to convert the molecule to the corresponding saturated, non-cylcic molecule

in normal molecules; 2n+2 in alkene; 2n in alkyne; 2n-2 -ignore oxygen and sulfur - subtract the number of nitrogens general formula; 2C+2+N-H-X/2 where N= # Nitrogen H= # of Hydrogens X= number of halogens

• electromagnetic spectrum has different wavelengths and frequencies for each region

the distance between succesvie crests and troughts

the number of waves which pass a point every second

can be absorbed by certain nuclei; causing them to reverse their spin - they are used in NMR and can give info about the environemnt of certain atoms

cause molecules to increase their rotational energy; this can give information about bond lengths

absorved by certain bonds and cause them to stretch or bend; gives information about bonds in a molecule

can produce electronic transitions and gie information about the electronic energy levels within the atom or molecule

used to identify bonds in a molecule