# Determine percent Nickel in Coin?

I've been trying for hours to figure out this problem and am unable to do so.

First, I graphed the concentration v. absorbance and found a best fit trend line. Then I can plug in the absorbance to find concentration.

What I DON'T know how to do is find the concentration of coin. I know I need it to find percent of Nickel. If you could please help me out with this, that would be greatly appreciated!

The coin has a mass of 3.2844 g.  It is dissolved in 42 mL nitric acid then placed in a 500 mL volumetric flask and water added to the line.  The resulting solution is greenish-blue.  They then pipet 1.0 mL of the coin solution into a 100 mL volumetric flask (filling to volume) and then  measure an absorbance value of 0.066 in a UV-Vis spectrometer at the appropriate wavelength.

The calibration data for the spectrometer are shown below:

Solution 1 (125 ppm Ni).  Absorbance = 0.200

Solution 2 (60 ppm Ni). Absorbance = 0.094

Solution 3 (32 ppm Ni). Absorbance = 0.047

Solution 4 (15 ppm N)i. Absorbance = 0.024

Solution 5 (12 ppm Ni). Absorbance = 0.020

Solution 6 (4 ppm Ni).  Absorbance = 0.006

What was the concentration of Ni in the coin (expressed as a % of the total mass)?

### Re: Determine percent Nickel in Coin?

Use the calibration graph to find ppm Ni2+ in the sample taken.
Convert this into g/mL
In the 100mL flask, mass of Zn would be 100 times this mass.
In the 500mL flask, there would be 500 times this amount, and this came from the mass of coin taken

### Re: Determine percent Nickel in Coin?

kingchemist wrote:
Use the calibration graph to find ppm Ni2+ in the sample taken.
Convert this into g/mL
In the 100mL flask, mass of Zn would be 100 times this mass.
In the 500mL flask, there would be 500 times this amount, and this came from the mass of coin taken

Thank you very much, your answer cleared up the concept behind the lab as well.