Honors Chemistry
Name: _______________________________________ Date: _______________ Mods: __________
Even More Henderson-Hasselbalch Practice . . .
Directions: Use the H-H equation to solve the following problems. You may need to first find a
concentration for the weak acid or conjugate base using the information provided.
1) An aqueous solution of lactic acid (HC3H5O3; Ka = 1.4 x 10-4) is prepared by dissolving 0.013
moles of lactic acid in 65 mL of water. A solution of potassium lactate is prepared by
dissolving 0.011 moles of potassium lactate in 75 mL of water. If these two solutions are
combined to form a buffer, what would be its pH?
2) Calculate the Ka of a buffer that is 0.120 M in propionic acid (HC3H5O2) and 0.105 M in lithium
propionate (LiC3H5O2) if the pH is 4.83.
3) A buffer is prepared by adding 20.0 g of acetic acid (HC2H3O2; Ka = 1.8 x 10-5) and 20.0 g of
sodium acetate (NaC2H3O2) to enough water to form 2.00 L of solution. What is the pH of this
buffer?
4) What is the ratio of HCO3- to H2CO3 in blood of pH 7.4? The Ka of H2CO3 is 4.3 x 10-7.
5) How many moles of sodium hypobromite (NaBrO) should be added to 2.00 L of 0.050 M
hypobromous acid (HBrO; Ka = 2.5 x 10-9) to form a buffer solution of pH 9.15? Assume that
no volume change occurs when the NaBrO is added.
6) A buffer solution contains 0.10 moles of nitrous acid (HNO2; Ka = 4.5 x 10-4) and 0.13 moles of
potassium nitrite (KNO2) in 1500 mL of water. What is the pH of this buffer?
7) How many grams of sodium lactate (NaC3H5O3) should be added to 1.25 L of 0.150 M lactic
acid (HC3H5O3; Ka = 1.4 x 10-4) to form a buffer solution with a pH of 4.00? Assume that no
volume change occurs when the NaC3H5O3 is added.
8) A buffer, consisting of H2PO4- and HPO42-, helps control the pH of physiological fluids. Many
carbonated soft drinks also use this buffer system. What is the pH of a soft drink in which the
major buffer ingredients are 6.5 g of NaH2PO4 and 8.0 g of Na2HPO4 per 355 mL of solution?
The Ka of H2PO4- is 6.2 x 10-8.