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Which is the (OH-) of a acetic acid solution of 0.032m?a. 7.56x10^-4b. 1.32x10^-11c. 10.88d. 3.12

User ESL
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1 Answer

21 votes
21 votes

So for the Ka of acetic acid I have used the value which is well used in many websites = 1.8*10^-5

From the ICE table we have

HA + H2O -> H3O+ + A-

I 0.032 0M 0M

C -x +x +x

E 0.032 - x +x +x

Now using the equilibrium formula:

Ka = [H3O+] * [A-]/[HA]

1.8*10^-5 = x^2/0.032 - x

Since this x will give a small number we can "ignore" it, therefore,

1.8*10^-5 = x^2/0.032

x^2 = 5.76*10^7

x = 7.59*10^-4, this is the concentration of H+

Now let's use our pH formula

pH = -log [7.59*10^-4]

pH = 3.12

Now we have the pH, the pOH will be = 14 - 3.12

pOH = 10.88

If we check letter B

pOH = -log [1.32*10^-11]

pOH will be equal to 10.88 exactly

Therefore, letter B is the correct one

User Jtpereyda
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