through experimentation you determine the following average k value for copper a
ID: 901408 • Letter: T
Question
through experimentation you determine the following average k value for copper and nickel: k775 cu2+= 12.1 M-1; k395 Ni2+=5.32 M-1. You are asked to analyze an unknown sample that cossets of both copper and nickel. At a wavelength of 775 nm, the sample has an absorbance of 0.416 and at a wavelength of 395 nm, the sample has an absorbance of 0.938.
create formulas to find the k value of for copper at 775nm, k value for nickel at 775 nm, and the k value for nickel at 395 nm. Then,using those k values, create a formula to find the concentration of Cu2+ and Ni2+ (I just need to set these problems up, actual numbers will be obtained in lab) so, five equations total.
Explanation / Answer
K775 Cu2+ = 12.1 M-1
K395 Ni2+ = 5.32 M-1
A775 = 0.416
A395 = 0.938
We know that at 395, only Ni2+ absorbs
A395 = K395Ni(II) * [Ni2+] + K395Cu(II) * [Cu2+]
= K395 [Ni2+] + 0
0.938 = 5.32 [Ni2+]
[Ni2+] = 0.938 / 5.32
[Ni2+] = 0.176 M
A775 = K755 Ni(II) [Ni2+]
0.416 = K755 Ni(II) * 0.176
K755 Ni(II) = 2.36 M-1
At 775 nm both Ni2+ and Cu2+ absorbs
A775 = K775 Ni(II) [Ni(2+)] + K775 Cu(II) [Cu(2+)]
0.416 = 2.36 * 0.176 + 12.1 [Cu2+]
0.416 = 0.415 + 12.1 [Cu2+]
0.001 = 12.1 [Cu2+]
[Cu2+] = 8.26 x 10-5 M
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