Chem Question?

Question

A calibration curve for absorbance versus concentration of Copper (Cu^2+) was prepared and the equation of the line was found to be y=50.1x.

A) If the absorbance of an unknown copper solution was found to be 0.150, what is the concentration of the unknown?

B) If the mass used to make that unknown from above was 1.03g and it was made in a 100mL volumetric flask, what is the % copper in that unknown solution?

Answer 1

First of all you need to specify if the concentration is expressed in mole/L (in standard curves you can express it in many different ways).

Assuming that this is the case the answer is very simple
y=50.1x=0.150 so just do the math to find x

As for B... the atomic mass of copper is 63.5
Since mole=M*V and also mole=mass/MW you have
mass/MW= M*V => mass= M*V*MW
M=x that you calculated
V you know but should be expressed in L,
MW=63.5

So % is (mass copper/mass sample)*100% = (M*V*MW/1.03)*100%