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. 5.29 times lower [H+] than the gastric juice
B. A million times higher [H+] than the gastric
juice
C. 6000 times lower [H+] than the gastric juice
D. A million times lower [H+] than the gastric
juice
E. 0.189 times the [H+] as 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. 5.29 times lower [H+] than the gastric juice
B. A million times higher [H+] than the gastric
juice
C. 6000 times lower [H+] than the gastric juice
D. A million times lower [H+] than the gastric
juice *
E. 0.189 times the [H+] as the gastric juice
WEAK acids
(proton donor)
and bases in biochemistry…
(proton acceptor)
Tendency of an acid to dissociate HA<--> H+ + A- is described by
Ka = ([H+][A-])/[HA]
pKa = -log Ka
WEAK acids
(proton donor)
and bases in biochemistry…
(proton acceptor)
Tendency of an acid to dissociate HA<-> H+ + AKa = ([H+][A-])/[HA]
is described by
pKa = -log Ka
Conjugate acid-base pair
Low Ka, high pKa
High Ka, low pKa
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?
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.
Which of the following correctly describe(s) the parameter pKa?
(1) 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
Which of the following correctly describe(s) the parameter pKa?
(1) 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*
Phosphoric acid, H3PO4 , is triprotic, with pKas of 2.14, 6.86, and
12.4. The ionic form that predominates at pH 3.2 is:
A. H3PO4
B. H2PO4—
C. H3PO3—
D. HPO4 2—
E. PO4 3—
1. Phosphoric acid, H3PO4 , is triprotic, with pKas of 2.14, 6.86, and 12.4. The ionic
form that predominates at pH 3.2 is:
A. H3PO4
B. H2PO4—*
C. H3PO3—
D. HPO4 2—
E. PO4 3—.
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)
A. Wash the area with dilute vinegar or lemon juice (both acidic)
B. 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
A. Wash the area with dilute vinegar or lemon juice (both acidic)
B. 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*