Question

Household bleach is an aqueous solution of sodium hypochlorite (NaClO). For a kinetics experiment, 10 mL of a 4%(w/w) bleach solution was diluted in a 100 mL volumetric flask. 5 mL of this diluted solution is added to 5 mL of dye in a reaction vessel. What is the concentration of bleach (in M) in the reaction vessel? Assume the density of the bleach solution is 1.11 g/mL.

Answer 1

4%(w/w) means 4 g of sodium hypochlorite (NaClO) present in 100 g of bleach solution.

So 0.4 g of sodium hypochlorite (NaClO) present in 10 g of bleach solution.

10 g = 10 x 1.11 g/mL = 11.1 mL of bleach solution.

Molarity = [0.4 g/ 74.44 g/mol] x [1000/11.1 mL] = 0.4841 M

now this solution is diluted to a final volume of 100 mL

M1 = 0.4841 M, V1 = 11.1 mL; M2 =?; V2 = 100 mL

M2 = [0.4841 M x 11.1 mL] / 100 mL = 0.0537 M

concentration of bleach after diluted to 100 mL = 0.0537 M

Now 5 mL of 0.0537 M bleach solution was further diluted by 5 mL of dye to a final volume of 10 mL

Final concentration of bleach (in M) in the reaction vessel = [0.0537 M x 5 mL] / 10 mL = 0.027 M

Final concentration of bleach (in M) in the reaction vessel = 0.027 M

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