Chapter 18, section 3
1. What is the expression for the ion product of water?
Kw = [H+][OH-]
2. What is the ion product of water, Kw, equal to?
Kw = 1 X 10-14
3. Use Le Chatelier’s Principle to explain what happens to the [OH-] in water when the [H+]
increases and vice versa.
H2O
H+ + OH[OH-] increases when [H+] and vice versa
When stress is applied, equilibrium shifts.
4. What is the formula for determining pH?
pH = -log[H+]
5. Use the formula in #4 to calculate the pH of the following solutions:
a. [H+] = 0.0055M
pH = -log(0.0055M) = 2.26
b. [H+] = 0.000084 M
pH = -log(0.000084) = 4.08
c. 0.0095 M
pH = -log(0.0095 M) = 2.02
d. [OH-] = 0.000033M
pOH = - log (0.000033 M) = 4.48, pH = 14 – 4.48 = 9.52
6. If pH = -log [H+], then [H+] = antilog (-pH). For example, the [H+] of a solution with pH = 7.40 is
equal to: antilog (-7.40) = 4.0 X 10-8 M. Determine the [H+] for the following substances:
a. Milk, pH = 6.50
Antilog (-6.50) = 3.2 X 10-7M
b. Lemon juice, pH = 2.37
Antilog (-2.37) = 4.3 X 10-3M
c. Milk of Magnesia, pH = 10.50
Antilog (-10.50) = 3.2 X 10-11M
d. Household ammonia, pH = 11.90
Antilog (-11.90) = 1.3 X 10-12 M
e. Seawater, pOH = 5.60
pH = 14 – 5.60 = 8.4
Antilog (-8.4) = 4 X 10-9
Section 4
7. What is an acid-base titration and what is it used for?
Method for determining the concentration of a solution by reacting a known volume of that
solution with a solution of known concentration.
8. What is the titrant in a titration?
The solution of known concentration.
9. What is the equivalence point?
Point at which the moles of H+ = moles of OH10. What is the end point?
Point at which the pH indicator changes color.
11. What is the molarity of household ammonia cleaning solution if 49.90 mL of 0.5900 M HCl is
required to neutralize 25.00 mL of the solution?
NH3 + HCl
NH4+ + Cl0.5900 mols HCl
1L
= 1.178 mols / L
X 49.90 ml
1
X 1L
1000 ml
X
1 mol NH3 X
1
1 mol HCl
25.00 ml
X
1000ml
1L