Final answer:
To find the initial concentrations after mixing the solutions, calculate the moles of each solute, add the volumes, and divide the moles by the total volume. This results in an initial [Fe3+] of 0.002 M and [SCN-] of 0.0005 M.
Step-by-step explanation:
To calculate the initial concentrations of [Fe3+] and [SCN-] after mixing 20 mL of 0.006 M Fe(NO3)3, 20mL of 0.0015 M KSCN, and 20mL of distilled water, we must consider the dilution of each solution when they are combined.
First we find the moles of Fe3+ and SCN- before mixing:
- Moles of Fe3+ = 0.006 M * 0.020 L = 0.00012 mol
- Moles of SCN- = 0.0015 M * 0.020 L = 0.00003 mol
The total volume after mixing is 20 mL + 20 mL + 20 mL = 60 mL or 0.060 L. Thus, we can calculate the initial concentrations in the mixture:
- [Fe3+] = 0.00012 mol / 0.060 L = 0.002 M
- [SCN-] = 0.00003 mol / 0.060 L = 0.0005 M