Question

An analysis of a commercial bleach sample provided the data in the following table. Complete the analysis for Trail 1 (See report Sheet.) of the bleach sample. Record the calculated values with the correct number of significant figures. 6. b. For trials 2 and 3, the percents available chlorine were 5.85% and 6.01% respectively. a. What is the average percent available chlorine for the bleach sample? b. What are the standard deviation and the relative standard deviation (%RSD) of available chlorine for the bleach sample?

Answer 1

1. Moles of Na2S2O3---->0.135mol/Lx0.03375L=0.0046mol (notice your calculation is wrong)

2.the reaction should be:

$2H^++OCl^-+2S_2O_3^{2-}\rightarrow Cl^-+S_4O_6^{2-}+H_2O$

So the moles of OCl-:

$molOCl^-=molS_2O_3^{2-}\times\frac{1molOCl^{-}}{2molS_2O_3^{2-}}$

$molOCl^-=0.0046\times\frac{1molOCl^{-}}{2molS_2O_3^{2-}}=0.0023molOCl^-$<------number 2

3)

According to the definitions of available chlorine the moles should be the same as above 0.0023mol

4)

The mass is converting the moles into grams of NaOCl:

$0.0023molNaOCl*\frac{74.45g}{1mol}=0.1712gNaOCl$

5)

the percent available is in the total sample (weight=2.71g):

$\frac{0.1712gNaOCl}{2.71g}*100=6.319\%$