I plotted absorbance on y and calculated Cu on x to get a tr

I plotted absorbance on y and calculated Cu on x to get a trendline of y= 72.45x. I assume I plotted this right and it\'s not the other way around?

Then in the second part the absorbence for a specific copper complex. I measured it wih the spectrophotometer and got this:

I did the calculations in paint after uploading, sorry for the bad quality.

Absorbance I got was 0.275, so I substituted that as the y in the trendline, and found 0.0038 as the concentration per L. Then since the stock solution was only 100mL I divided that by 10 to get the moles in 100mL then multiplied by the copper molar mass of 63.5 to get 0.025grams of Copper.

Since the initial measured copper was 0.105 I divided 0.025/0.105 x 100 to get percentage copper asked in #3, which was about 24%. The complex the copper sample was taken from is CuSO4-5H2O with a molar mass of ~250, so the copper in it is about 25%, close to what I got.

Just wanted to make sure I did my calculations right in order to get copper mass and % copper. If anyone can check and see.

Data Table I Volume of Volume of NH3 (aq) Total Volume Calculated [Cu2] Absorbance Solution # Stock 2O 3.0 | 0.25O o 048 O. COo 2 (o 0 (2 Equation of the line from the graph 4 2-, 45- 70

Solution

Estimation of Cu percentage in a sample

The calculations done as described above looks alright

So yes the percentage of Cu cslculated is correct here.