Hello, I am struggling to find the answer to this problem. The experiment used 8

Question

Hello,

I am struggling to find the answer to this problem. The experiment used 8 test tubes all with different volumes of KCSN, Fe(NO3)3 and H20. We used a spectroscope to find the absorbance and were asked to calculate the total added SCN- concentration and the total added Fe3+ concentration. My professor gave us the calculation:

mL of KCSN / mL of solution * Molarity of stock solution

This equation gives me the molarity of KCSN in the solution, but I am not sure how to get just the molarity (concentration) of the SCN- in the solution. Below is a sample of my data.

5 mL KCSN

.5 mL Fe(NO3)3

14.5 mL of H20

Total added SCN- concentration=???

Total added Fe3+ concentration=???

Absorbance=.283

When I calculated the molarity of KSCN in the solution I got 1.25x10^-4.

I am not asking for someone to do all of my homework for me, but need some advice as to how to get to SCN- concentration from where I am at! Any help would be lovely!

Explanation / Answer

Since, All the Pottasium salts are salts of strong bases thus we can say this dissolves and ionates immendiately

Hence the Molarity of KSCN solution = Molarity of SCN- = 1.25*10^-4

For the concentration of Fe 3+ we need the molarity of Fe(NO3)2 solution or the wieght of it added

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