What should the absorbance be if light is passed through the same - ProProfs Discuss

# What should the absorbance be if light is passed through the same solution at the same wavelength and the light path is reduced to 1 cm? Light is passed through a solution with a light path of 2 cm and the absorbance is recorded as 0.40.

A. 0.80
B. 0.40
C. 0.20
D. 0.10

This question is part of Chemistry Quiz 2
Asked by J_black, Last updated: Nov 05, 2018

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3 Answers

#### M. Kennedy

M. KennedyWeb Content Writer, Denver
Web Content Writer, Denver

Answered on Nov 05, 2018

In a math word problem, it is common to use a formula. In this case when the math word problem includes absorbance and wave length, then the formula should be used where the absorbance amount is equal to the amount of the molar absorptivity multiplied by the pathlength and multiplied that by the concentration amount. With that said, the problem gives the amount being absorbed, so the answer on the left of the equal side is given at 0.40. The light path is 2 centimeters and it is reduced to 1 cm.

When plugging in the numbers, the answer will come out to be 0.20 based on having to divide 0.40 by the light path amount of two after moving some of the numbers around to get the variable on one side.

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#### John Adney

John Adney

Answered on Jan 09, 2017

Absorbance = elc where e = molar absorptivity, l = pathlength and c = concentration
0.40 = e x 2 x c
Since e is a constant,

c = 0.40/2
c = 0.20
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#### John Smith

John Smith

Answered on Oct 26, 2016

0.20
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