The active ingredient in commercial bleach is sodium hypochlorde, `NaOCl`, which can be determined by iodometric analysis as indicated in these equations.
`OCI^(-)+2H^(+)+2I^(-)rarrI_(2)+Cl^(-)+H_(2)O`
`I_(2)+2S_(2)O_(3)^(2-)rarrS_(4)O_(6)^(2-)+2I^(-)`
If 1.356 g of a bleach sample requires 19.50 mL of 0.100 M `Na_(2)S_(2)O_(3)` solution, what is the percentage by mass of `NaOCl` in the bleach?
A. `2.68%`
B. `3.70%`
C. `5.35%`
D. `10.7%`
