Question

A student prepared a series of solutions of copper (II) sulfate of known concentration and measure their absorbance at $600nm$ is a colorimeter. A graph of the absorbance vs. concentration for these solutions is shown below.
The student then measured the absorbance of the unknown solution and found it to be $0.55$.
What is the concentration of the unknown solution?

• A. $0.28M$
• B. $0.55M$
• C. $0.83M$
• D. $1.1M$

Answer 1

The correct option is A $0.28M$

According to Beer's law of determining concentration;

Absorbance $=\left(e\right)\left(L\right)\left(Concentration\right)$

$\Rightarrow \left(0.55\right)=\left(2\right)\left(Concentration\right)$

Slope of graph $=2$, So, $e=L=2$

$\Rightarrow Concentration=0.28M$