Clorox bleach is mainly made of S.25% NaClO which a amount to a concentration of

Question

Clorox bleach is mainly made of S.25% NaClO which a amount to a concentration of approximately 0.704 M. Note that K_a = 3.4 times 10^-3. a. Determine the approximate pH of this solution. b. What is the approximate percent ionization of this bleach solution? Based on the percent ionization was the approximation made to calculate the pH valid? (Answer both questions) c. When using bleach to clean clothes it is recommended that it be diluted by having 4 ounces of bleach (half a cup) in 128 ounces of water (one gallon). Determine the approximate pH of the diluted bleach. d. What is the approximate percent ionization of the diluted bleach solution? Based on the percent ionization was the approximation made to calculate the pH valid? (Answer both questions)

Explanation / Answer

22. a. 0.704 M NaClO

ClO- + H2O <==> HClO + OH-

Kb = [HClO][OH-]/[ClO-]

with x amount dissociated

1 x 10^-14/3.4 x 10^-7 = x^2/0.704

x = [OH-] = 1.44 x 10^-4 M

pOH = -log[OH-] = 3.842

pH = 14 - pOH = 10.16

b. % ionization = [H+] x 100/[ClO-]

                           = 1.44 x 10^-4 x 100/0.704

                           = 0.020%

c. convert ouncess to Liter

concentration of diluted bleach solution = 0.118 ml bleach x 0.704 M/3.785 L = 0.022 M

pH calculation,

1 x 10^-14/3.4 x 10^-7 = x^2/0.022

x = [OH-] = 2.54 x 10^-5 M

pOH = -log[OH-] = 4.59

pH = 14 - pOH = 9.40

d. % ionization = 2.54 x 10^-5 x 100/0.022 = 0.115%

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