What is the Average Molarity of Sodium Hypochlorite in a Titration Experiment?

[chemnerd666]

Homework Statement

I am required to determine an average molarity for sodium hypochlorite solution, the experiment involved titrating 10 mL of 1:10 diluted bleach (sodium hypochlorite) with sodium thiosulfate, the volumes of titrant used to reach endpoint are, 17.95 mL, 18.31 mL and 18.21 mL, respectively. The molarity of sodium thiosulfate was determined to be 0.072 M in the previous section.

Homework Equations

the reaction equation is:
2 Na2S2O3(aq) + NaClO(aq) + H2O(aq) → Na2S4O6(aq) + NaCl(aq) + 2 NaOH(aq)

net ionic equation:
2 S2O32-(aq) + ClO-(aq) + H2O (l) → S4O62-(aq) + Cl-(aq) + 2 OH-(aq)

The Attempt at a Solution

I am unsure how to use this information to find 3 values for the molarity of sodium hypochlorite,

 

[Nino MMP]

since sodium thiosulfate is the titrant, and not sodium hypochlorite. I used the formula M1V1=M2V2 to find that the molarity of sodium hypochlorite is 0.0084 M. However, I don't know how to find the average molarity of sodium hypochlorite since I only have one value.