Question

What concentration range of ASA will provide %T values of 20%-70% when measured in a 1.00cm cell if the wavelength selected is 235nm and the molar absorbtivity of ASA is 6.16x10^3.

Answer 1

A = ecl

Where A = absorbance

e = molar absorptivity = 6.16 x 10³ M^-1 cm^-1

c = concentration

l = path length = 1.00 cm (given)

Now absorbance and transmittance are related with the following equation:

A = 2 - log%T

where, T = transmittance

Thus,

2 - log%T = ecl

or, 2 - log20 = 6.16 x 10³ x c x 1         (For 20% transmittance)

or, 2 - 1.30 = 6.16 x 10³ x c

or, c = 0.7/ (6.16 x 10³)

or, c = 0.11 x 10^-3 M

        = 0.11 mM (mM stands for millimolar)

For 70% transmittance

2 - log70 = 6.16 x 10³ x c x 1

or, 2 - 1.85 = 6.16 x 10³ x c

or, c = 0.15/(6.16 x 10³)

or, c = 0.024 x 10^-3 M

        = 0.024 mM

Therefore, the concentration range of ASA = 0.024 mM to 0.11 mM