Question

5.00 mL of .00500 M ferric nitrate is added to 5.00 mL of nitric acid and 10.0 mL of .00250 M thiocyanate solution. Calculate the intial Fe^3+ concentration before reaction.

So how do I go about doing this?

Answer 1

5.00 mL x 0.005 M = 0.025 millimoles Fe^+3.
What is the volume? I see 5 mL + 5 mL + 10 mL = 20 mL. So the initial concn is 0.025 millimoles/20 mL = ?? M

If you would rather work as a dilution, it can be done this way:
0.005 M has been diluted by a factor of 5.00 mL/20.00 mL = ?? M
Both answers should be the same.

Answer 2

0.00125