Question

The transmittance of a solution 1.00cm thick of unknown concentration is 0.700. The transmittance of a standard solution of the same material is also 0.700. The concentration of the standard solution is 100.0 ppm; the cell length of the standard is 4.00 cm. What is the concentration of the unknown solution?

Answer 1

solution :-

lets convert the transmitance to the absorbance

A= 2- log % T

Absorbance of the standard solution

A= 2 – log 0.700

= 2.1549

Now lets calculate the molar absorptivity coefficient

A= * b*c

2.1549 = *4.0 cm * 100 ppm

2.1549/4.0 cm*100 ppm =

0.005387 =

now using the molar absorptivity coeffcient lets calculate the concentration of the unknown solution

A= *b*b

2.1549 = 0.005387 * 1.0 cm * c

2.1549 / 0.005387 * 1.0 cm = c

400 ppm = c

so the concnetration of the unknown solution is 400 ppm