TA : Sarah Wondmeneh
27 March, 2013
Experiment – 5 Pre-Lab
1. The light absorbance is an experimentally measured quantity which is directly
proportional to the concentration of the solution. This means that when absorbance is
measured through a light-sensitive machine such as a spectrophotometer, the level of
absorbance of a particular wavelength of light increases as the concentration of the
solution increases given that the wavelength is kept unchanged. The following
equation demonstrates the relationship between the light absorbance and concentration of
Where ‘A’ is the absorbance of light and ‘ ’ is a constant known as molar absorptivity
constant. ‘cx’ measures the concentration of the sample solution while ‘I’ represents the
path length in centimeters.
2. Rate constant is a proportionality constant that is specific for a given reaction at a given
temperature and does not change as the reaction proceeds.
3. Assuming the rate of a reaction has the unit Mol/sec in the reaction
Zero order reaction: when the rate of reaction does not change when the
concentration of the reactants change, the rate is independent of the concentration.
o [ ]
o Unit = Mol/sec
First order reaction: If the rate doubles when the concentration of the reactants are
doubled, the rate depends on [A] to the exponent/order 1, [A] .
o Unit = sec
Second order reaction: If the rate quadruples when the concentration of reactants