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?

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.

0.00125

To calculate the initial concentration of Fe^3+ before the reaction, you need to use the concept of stoichiometry. Here's how you can approach this problem:

1. Begin by writing the balanced chemical equation for the reaction that occurs between ferric nitrate, nitric acid, and thiocyanate solution. The reaction can be represented as follows:
Fe(NO3)3 + 3 HNO3 + 3 KSCN → Fe(SCN)3 + 3 KNO3 + 3 H2O

2. Determine the number of moles of ferric nitrate (Fe(NO3)3) present in 5.00 mL of a 0.00500 M solution. To do this, you need to use the formula:
moles = concentration × volume (in L)

Convert the volume from mL to L by dividing by 1000:
volume = 5.00 mL ÷ 1000 = 0.00500 L

Now, calculate the number of moles of ferric nitrate:
moles of Fe(NO3)3 = 0.00500 L × 0.00500 M

3. From the balanced chemical equation, you can see that 1 mole of Fe(NO3)3 produces 1 mole of Fe^3+. Therefore, the initial moles of Fe^3+ are the same as the moles of ferric nitrate.

4. Finally, you need to find the concentration of Fe^3+ ions by dividing the moles by the total volume of the solution.
Total volume = 5.00 mL (Fe(NO3)3 solution) + 5.00 mL (nitric acid) + 10.0 mL (thiocyanate solution)
Convert the total volume to liters by dividing by 1000:
total volume = (5.00 mL + 5.00 mL + 10.0 mL) ÷ 1000 = 0.0200 L

Now, calculate the initial concentration of Fe^3+ ions:
concentration of Fe^3+ = moles of Fe^3+ ÷ total volume

By following these steps, you can calculate the initial Fe^3+ concentration before the reaction.