Question

After creating a Beer's Law plot using standard solutions of Q, you determined the slope of Beer's Law to be 0.543 M-1. Your unknown solution of Q tested in Part B of the experiment had an absorbance of 0.144. Determine the concentration (in molarity) of the unknown solution Q from Part B. Do not use scientific notation or units in your response. If Carmen adds zeros after the decimal place, your answer will still be graded correctly.

Answer 1

Answer : The concentration (in molarity) of the unknown solution Q is, 0.265

Explanation :

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

From the Beer's Law plot between absorbance and concentration we concldue that the slope is equal to $\epsilon \times l$  and path length is 1 cm.

As we are given that:

Slope = 0.543 M⁻¹

and,

Slope = $\epsilon \times l$

$\epsilon \times l=0.543M^{-1}$

$\epsilon \times 1cm=0.543M^{-1}$

$\epsilon=0.543M^{-1}cm^{-1}$

Now we have to determine the concentration (in molarity) of the unknown solution Q.

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

$0.144=0.543M^{-1}cm^{-1}\times C\times 1cm$

$C=0.265M$

Therefore, the concentration (in molarity) of the unknown solution Q is, 0.265