1. A. 5.29 times lower [H+] than the gastric juice
The pH of a sample of blood is 7.4; the pH of a sample of gastric juice is 1.4. The blood sample has:
A times lower [H+] than the gastric juice
B. A million times higher [H+] than the gastric
juice
C times lower [H+] than the gastric juice
D. A million times lower [H+] than the gastric
E times the [H+] as the gastric juice
This question is to remind students of the logarithmic nature of the pH scale; this seems to be a common problem, though, once they are reminded, it is not a hard concept. This could be used BEFORE the pKa TT.

2. The pH of a sample of blood is 7
The pH of a sample of blood is 7.4; the pH of a sample of gastric juice is 1.4. The blood sample has:
A times lower [H+] than the gastric juice
B. A million times higher [H+] than the gastric
juice
C times lower [H+] than the gastric juice
D. A million times lower [H+] than the gastric
juice *
E times the [H+] as the gastric juice

3. WEAK acids and bases in biochemistry…
Tendency of an acid to dissociate HA<--> H+ + A- is described by
Ka = ([H+][A-])/[HA] pKa = -log Ka
(proton donor) (proton acceptor)
This next three slide sequence can be used to set up the following In class activity, and then the Clicker questions

4. WEAK acids and bases in biochemistry…
Tendency of an acid to dissociate HA<-> H+ + A- is described by
Ka = ([H+][A-])/[HA] pKa = -log Ka
(proton donor) (proton acceptor)
Conjugate acid-base pair
Low Ka, high pKa
High Ka, low pKa

6. -Which is the stronger acid?
Formic acid has a pKa of 3.75; acetic acid has a pKa of 4.76.
-Which is the stronger acid?
-Does the stronger acid have a greater or lesser tendency to lose its proton than the weaker acid?
-DRAW the titration curves of formic and acetic acids, on one graph.
-At a solution pH of 4.76, what can you say about the concentrations of acetic acid (CH3COOH) and acetate (CH3COO-) present?
In class small group activity

7. Formic acid has a pKa of 3.75; acetic acid has a pKa of 4.76.
-Which is the stronger acid?
-Does the stronger acid have a greater or lesser tendency to lose its proton than the weaker acid?
Formic acid is the stronger acid. It has a greater tendency to lose its proton than acetic acid; it "wants" to give away its proton.
-DRAW the titration curves of formic and acetic acids, on one graph.
(small group activity, with answers presented on the board)
-At a solution pH of 4.76, what can you say about the concentrations of acetic acid (CH3COOH) and acetate (CH3COO-) present?
At a solution pH of 4.76, the concentrations of acetic acid and acetate will be equal.
Answer slide for in-class activity

8. Which of the following correctly describe(s) the parameter pKa?
the negative logarithm of the hydrogen ion concentration of an
aqueous solution
(2) a standard way to measure the [H+] concentration in an aqueous
solution.
(3) the negative logarithm of an equilibrium (or dissociation)
constant
(4) the pH at which a weak acid is one-half dissociated
(5) the pH at which there are equal concentrations of a weak acid
and its conjugate base
(6) the pH at which maximum buffering capacity of the conjugate
acid-base pair occurs
Too many answers for most audience response systems, so use as a discussion question...helps get at the common misconceptions.

9. Which of the following correctly describe(s) the parameter pKa?
the negative logarithm of the hydrogen ion concentration of an
aqueous solution
(2) a standard way to measure the [H+] concentration in an aqueous
solution.
(3) the negative logarithm of an equilibrium (or dissociation)
constant*
(4) the pH at which a weak acid is one-half dissociated*
(5) the pH at which there are equal concentrations of a weak acid
and its conjugate base*
(6) the pH at which maximum buffering capacity of the conjugate
acid-base pair occurs*
Too many answers for most audience response systems, so use as a discussion question...helps get at the common misconceptions.

10. Phosphoric acid, H3PO4 , is triprotic, with pKas of 2. 14, 6
Phosphoric acid, H3PO4 , is triprotic, with pKas of 2.14, 6.86, and The ionic form that predominates at pH 3.2 is:
A. H3PO4
B. H2PO4—
C. H3PO3—
D. HPO4 2—
E. PO4 3—

11. 1. Phosphoric acid, H3PO4 , is triprotic, with pKas of 2. 14, 6
1. Phosphoric acid, H3PO4 , is triprotic, with pKas of 2.14, 6.86, and The ionic form that predominates at pH 3.2 is:
A. H3PO4
B. H2PO4—*
C. H3PO3—
D. HPO4 2—
E. PO4 3—.

12. Catechols substituted with long chain alkyl groups are the components of poison ivy and poison oak that produce an annoying itchy rash (see structure below).
If you were exposed to poison ivy while out walking in the woods, which of the treatments below would you apply to the affected area in order to make the below offending chemical the MOST soluble so it can be washed away?
(pKa of the hydroxyl groups = 9)

13. Wash the area with dilute vinegar or lemon juice (both acidic)
Wash the area with soap and water (soap is a Na+ or K+ salt of fatty acids)
C. Wash the area with dilute vinegar or lemon juice and soap
D. Wash the area with water and baking soda (alkaline)
E. Wash with soap, water, and baking soda
This is a very advanced question; it gets at not only pKa, and solubility (more soluble when charged) but also has to do with other biomolecules, hydrophobicity, and detergents, so, it would come after further topics in the course.

14. Wash the area with dilute vinegar or lemon juice (both acidic)
Wash the area with soap and water (soap is a Na+ or K+ salt of fatty acids)
C. Wash the area with dilute vinegar or lemon juice and soap
D. Wash the area with water and baking soda (alkaline)
E. Wash with soap, water, and baking soda*
The answer requires that the students know that they want to make the –OH groups into charged –O- (negatively charged) groups, so they need to use a higher pH wash that will allow the proton to be released; they also need soap (a detergent, something that is amphipathic)