SCH4U
ACID/BASE
IN CLASS ASSIGNMENT
1. Lactic acid (HC3H5O3), which is present in sour milk, also gives sauerkraut its
tartness. It is monoprotic and in a 0.100 mol/L solution of lactic acid, the pH is 2.44 at
25 °C. Calculate the Ka for lactic acid at this temperature. (707)
2. Formic acid, HCOOH, is present in the sting of certain ants. What is the pH of a
0.025 mol/L solution of the acid if the Ka = 1.8 x 10-4? What is its proper IUPAC name?
What is the value of Kb for the HCOO- ion?
3. To study the effects of a weakly acid medium on the rate of corrosion of a metal alloy,
a student prepares a buffer solution by combining 0.11 M NaC2H3O2 and also 0.09M
HC2H3O2 (Ka=1.8 x 10-5). In general, what two things are used to make a buffer solution?
Which of these two things is which? Write the equilibrium reactions for each chemical.
Using one of these reactions, make a chart to calculate the pH of the buffer solution.
(727)
4. A 1.0 L buffer solution is prepared from 0.30 mol of acetic acid and 0.40 mol of
sodium acetate. Calculate the pH of this solution. What is the change in pH if 0.15 mol
of OH- are added to the original solution? What is the change in pH if 0.20 mol of H3O+
is instead added to the original solution?