Equivalence point concentration/number of moles

[drcasey]

Homework Statement

Fe[3+]+V[2+]-->Fe[2+]+V[3+]

If you start with 0.1000 M solutions and the first-named species is the titrant, what will be
the concentration of each reactant and product at the equivalence point of the titrations above? Assume that there is no change in [H+] during the titration.

Homework Equations

Keq=[V3+][Fe2+]/[V2+][Fe3+]=2.23X10^17

The Attempt at a Solution

I believe V2+ and Fe3+ will be the same at the equivalence points since that is the definition of the analyte and titrant. However, I was told that the V3+ and Fe2+ concentration is 0.1000/2. Could someone please explain why it is divided by 2 and not just 0.1000? Thank you

 

[symbolipoint]

Stoichiometry should be enough. Write the balanced reaction. You are using 1 to 1 mole ratio for the reaction. How does this relate to volume of titrant and volume of analyte solution? The resulting volume, if both concentrations are 0.1000, should be...? Think... you will see.

 

[drcasey]

Ok just to make sure. The total volume will be 2L? Because of that, we take 0.1000mol/2?

 

[Borek]

Ok just to make sure. The total volume will be 2L? Because of that, we take 0.1000mol/2?

Yes, just a simple dilution.

 

[DeeNos]

for your time.

At the equivalence point of a titration, the number of moles of the titrant added is equal to the number of moles of the analyte. In this case, the titrant is V2+ and the analyte is Fe3+. Therefore, when the titration reaches the equivalence point, the concentration of V2+ will be 0.1000 M, since that is the initial concentration. However, the concentration of Fe3+ will be half of that, or 0.0500 M, since the stoichiometric ratio between V2+ and Fe3+ is 1:2. Similarly, the concentration of V3+ and Fe2+ will also be 0.0500 M at the equivalence point. This is because the reaction is balanced in a 1:1 ratio between these two species, so the concentration of each will be half of the initial concentration of 0.1000 M.