1. Calculate the average volume of Na2S2O3 needed for the titration of 25.00 mL of diluted bleach. 2. Use the average volume and molarity of Na2S2O3 to determine the molarity of the diluted bleach (hint: use the equations in the introduction). 3. Calculate the molarity of the commercial bleach. 4. Assume that the density of the commercial bleach is 1.08 g/mL. Calculate the percent by mass of NaCl in the commercial bleach. 5. Calculate the percent error of your value.

Explanation:

Determine the number of moles of sodium thiosulfate that are equivalent to one mole of sodium

hypochlorite.

2 S2O3

2− = I−

3 = I2 = ClO−, therefore, for every mole of sodium thiosulfate, we need one half of a

mole of sodium hypochlorite.

2. Calculate the average volume of Na2S2O3

to determine the molarity of the diluted bleach.

16.8 + 17.6

2

= 17.2

3. Use the average volume and molarity of Na2S2O3

to determine the molarity of the diluted bleach.

mol Na2S2O3 = (0.0172)(0.1) = 0.00172

⇓

(0.00172)

2

= 0.000852 mol NaClO

⇓

0.000852

0.025

= 0.341 M NaClO

4. Calculate the average molarity of the commercial bleach before it was diluted.

0.000852 × 4 = 0.0034

0.0034

0.005

= 0.68 M NaClO

5. Assume the density of the commercial bleach is 1.08 g/mL. Calculate the average percent by mass of

NaClO in the commercial bleach.

0.0034 × 74.4424 = 0.2536 g

5mL × 1.08 g/mL = 5.4g

0.2536

5.4 = 4.70%

6. From the label information of the commercial bleach calculate the average deviation of the three

titration values.

|0.047 − 0.060| = 0.013

7. Calculate the percent error of your value.