Question
If 20.0 mL of glacial acetic acid (pure HC2H3O2) is diluted to 1.30 L with water, what is the pH of the resulting solution? The density of glacial acetic acid is 1.05 g/mL.
Answers
How much will 1 L of glacial acetic acid weigh? 1000 mL x 1.05 g/mL = 1050 grams.
How much of that is acetic acid. If it's glacial acetic acid, it is 100% acetic acid so all 1050 g is HC2H3O2.
How many moles is that?
1050 grams/molar mass = 1050/60 = 17.50 M.
The new concn will be 17.5 M x (20 mL/1300 mL) = ?? M (or you can do a mL x M = mL x M and come up with the same thing).
Next the ionization.
HAc (easier to write than HC2H3O2) + H2O ==> H3O^+ + Ac^-
Ka = (H^+)(Ac^-)/(HAc) = 1.8 x 10^-5
Set up an ICE chart, calculate H^+, then convert to pH. Check my thinking.
How much of that is acetic acid. If it's glacial acetic acid, it is 100% acetic acid so all 1050 g is HC2H3O2.
How many moles is that?
1050 grams/molar mass = 1050/60 = 17.50 M.
The new concn will be 17.5 M x (20 mL/1300 mL) = ?? M (or you can do a mL x M = mL x M and come up with the same thing).
Next the ionization.
HAc (easier to write than HC2H3O2) + H2O ==> H3O^+ + Ac^-
Ka = (H^+)(Ac^-)/(HAc) = 1.8 x 10^-5
Set up an ICE chart, calculate H^+, then convert to pH. Check my thinking.
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