1.1 What is Chemistry?

http://www.ck12.org Chapter 21. Acids and Bases

• A salt formed from a strong acid and a strong base will form a neutral solution (pH = 7), because neither the
  cation nor the anion is a sufficiently strong acid or base.


• The deprotonated form of an acid is referred to as its conjugate base. Similarly, the protonated form of a base
  is referred to as its conjugate acid.


• A mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid) produces a buffer,
  which is resistant to large changes in pH even when additional acid or base is added.

Lesson Review Questions

1. What types of acids and bases form neutral salt solutions?


2. What types of acids and bases from basic salt solutions?


3. What types of acids and bases form acidic salt solutions?


4. Define conjugate acid and conjugate base in the general acid dissociation equation, HAH++ A−.


5. Write the formula and charge for the conjugate base of each of the following weak acids:
   a. HNO 2
   b. HCOOH
   c. C 6 H 5 COOH
   d. C 6 H 5 OH


6. Write the formula and charge for the conjugate acid of each of the following weak bases:
   a. CH 3 NH 2
   b. C 5 H 5 N
   c. C 6 H 5 NH 2


7. When NaF is dissolved in water, the following reaction occurs: F−+ H 2 OHF + OH−. The Kbfor this
   process is 1.4× 10 −^11. If a 0.1 M solution of NaF is prepared, what is the equilibrium concentration of HF?


8. What initial concentration of KCN is needed to provide an equilibrium HCN concentration of 0.0025 M? The
   Kbfor CN−is 2.0× 10 −^5.


9. Explain why buffer solutions are able to resist small changes in pH.


10. What ratio of benzoic acid to sodium benzoate should be used to prepare a buffer solution with a pH of 4.3?
    The Kafor benzoic acid is 6.5× 10 −^5.


11. What is the pH of a solution containing equal concentrations of formic acid and potassium formate? The Ka
    for formic acid is 1.7× 10 −^4.

Further Reading/Supplementary Links

• Acidic, basic, and neutral salts: http://www.science.uwaterloo.ca/~cchieh/cact/c123/salts.html


• Buffer solutions: http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Buffer-Solutions-620.html


• Buffer systems in the blood: http://www.chemistry.wustl.edu/~edudev/LabTutorials/Buffer/Buffer.html

Points to Consider

The pH of a system is very important for sustaining life. Biochemical processes require careful pH control in order
to maintain cellular integrity.