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1. A certain weak acid, HA, has a K a value of 9.6x10 -7 . Calculate the percent

ID: 511549 • Letter: 1

Question

1. A certain weak acid, HA, has a Ka value of 9.6x10-7. Calculate the percent ionization of HA in a 0.10 M solution.

2. Acetic acid, CH3CO2H, is the solute that gives vinegar its characteristic odor and sour taste. Calculate the concentration of OH- in 0.0123 M CH3CO2H.

3. Morphine (C4H9NO) is a weak organic base with pKb = 5.68. Calculate the pH in a 1.10 x 10-2M morpholine solution.

4. Sodium benzoate (C6H5CO2Na) is used as a food preservative. Calculate the concentrations of all species present (Na+, C6H5CO2, C6H5CO2H, H3O+ and OH) in 0.058 M sodium benzoate.

Explanation / Answer

1)

Ka = 9.6 x 10^-7

concentration = 0.1 M

[H+] = sqrt (Ka x C)

        =sqrt (9.6 x 10^-7 x 0.1)

       = 3.098 x 10^-4 M

% ionization = (H+ / C) x 100

                    = (3.098 x 10^-4 / 0.1) x 100

% ionization = 0.31 %

2)

C = 0.0123 M

Ka = 1.8 x 10^-5

[H+] = sqrt (1.8 x 10^-5 x 0.0123)

       = 4.705 x 10^-4 M

[OH-] = 2.12 x 10^-11 M