Question

Write the chemical equation for the ionization of acetic acid. CH3CO2H + H2O <---> H3O+ + CH3CO2-

From the pH, calculate the concentration of hydrogen ions. ( I KNOW TO USE THIS ph = -log[H+]) Next, find the concentration of theacetate ion. (I HAVE NO IDEA HOW TO DO THIS PART) How would the concentration of hydrogen ion be related to the acetate ion? (Hint: lookat the formula for acetic acid.) Considering that acetic acid is the source of hydrogen and acetate ions in this
sample, determine the actual concentration of acetic acid that is in the solution at the time when you measuredthe pH. Show a set of sample calculations.

You might develop a table like this one:

________________pH _________[H+] _________[C2H3O2​-] ________[H C2H3O2]

0.10 M acetic acid | 2.75 pH

0.010 M acetic acid | 3.20 pH

0.0010 M acetic acid| 3.60 pH

0.0001 M acetic acid | 4.05 pH

Answer 1

	pH	[H+]	[CH3COO-]	[CH3CO2H]
0.1M acetic acid	2.75	1.78 X 10^(-3)	1.78 X 10^(-3)	0.0982
0.010 M acetic acid	3.20	6.31 X 10^(-4)	6.31 X 10^(-4)	9.36 X 10^(-3)
0.0010 M acetic acid	3.60	2.51 X 10^(-4)	2.51 X 10^(-4)	7.49 X 10^(-4)
0.0001 M acetic acid	4.05	8.91 X 10^(-5)	8.91 X 10^(-5)	1.09 X 10^(-5)

Since for every H+ ion formed a CH3COO- is also formed because acetic acid dissociates as given in your equation

CH3CO2H + H2O <---> H3O+ + CH3CO2-

So concentration of acetate ion will be equal to [H+]

Acetic acid concentration at equilibrium will be = initial concentration – concentration of H+ or acetate ion

That is when initial concentration is 0.1 M and [H+] is 1.78 X 10^(-3)

[CH3CO2H] = 0.1-1.78 X 10^(-3) = 0.0982