Chemistry

Acids and Bases Problem Set Chem B11

Name_____________________________________ Lab Period_________________________________

Calculating [OH-] and [H3O+] using the Kw equation.

Kw = [H3O+][OH-]

1. Solve the Kw equation for both [H3O+] and [OH-]. You should have two different equations.

2. Using the Kw equation, convert the following concentrations either from [H3O+] to [OH-] or from [OH-] to [H3O+]

[H3O+]	[OH-]	[OH-]	[H3O+]
2.5 x 10-5 M		4.4 x 10-3 M
6.8 x 10-11 M		2.6 x 10-9 M
9.9 x 10-1 M		8.8 x 10-5 M
8.5 x 10-7 M		1.1 x 10-13 M

3. Calculate the pH of the following solutions. Remember that pH = -log([H3O+])

[H3O+]	pH	[OH-]	pH
1.0 x 10-8 M		8.9 x 10-3 M
5.2 x 10-9 M		6.5 x 10-6 M
2.3 x 10-3 M		4.5 x 10-2 M
4.6 x 10-4 M		9.9 x 10-13 M

4. Calculate the [H3O+] or [OH-] of solutions with the following pH values. Remember [H3O+] = 10-pH

pH	[H3O+]	pH	[OH-]
9.58		8.88
10.74		7.35
1.23		13.54
6.97		4.45

5. Identify the conjugate acid/base pairs in the following reactions. Circle one pair and draw squares around the other pair.

HCl + NaOH NaCl + H2O

HC2H3O2 + Na2HPO4 ↔ NaC2H3O2 + NaH2PO4

NH3 + H2CO3 ↔ NH4+ + HCO3-

6. Buffer Solutions: Using the list of strong acids and weak acids found on page 331 of your textbook, identify whether the solutions below would act as buffer solutions or not.

Solution	Is the solution a buffer? (Y/N)
1.0 M NaCl and 1.0 M HCl
0.5 M HCN and 1.0 M NaCN
0.75 M H3PO4 and 0.25 M NaH2PO4
1.0 M H2CO3 and 0.5 M Na2CO3
2.0 M HC2H3O2 and 1.0 M NaC2H3O2

7. Predict the products of the following reactions involving acids and bases. Make sure they are balanced as well. Identify the type of reaction happening. You may want to refer to section 10.7 in your book. For the first one, assume Fe becomes Fe3+.

__Fe + __HNO3

__HBr + __Ca(OH)2

__HCl + __CaCO3

__HClO3 + __LiHCO3

8. Answer the following questions based on the equilibrium reaction shown below:

HCN + H2O ↔ H3O+ + CN-

a. What would happen to the equilibrium if more HCN were added?

b. What would happen if some water were removed?

c. What would happen if HCl were added to the reaction mixture?

9. Consider the buffer system between the weak acid NaH2PO4 and Na2HPO4 to answer the following questions.

a. Which of the parts of the buffer system would neutralize added acid? Write out the reaction between that part of the buffer and H3O+.

b. Which of the parts of the buffer system would neutralize added base? Write the reaction between that part of the buffer and OH-.

3

Bakersfield College Wade Ellis