LHWHS AP Biology NAME______________
Unit One - The Chemistry of Life
Practice for Quiz #1
1. What are the pH, pOH, [H pH = 2.17 pOH = 11.83 [0H -
ANSWERS
+ ], and [OH
] = 1.48 x 10
_ ] of 0.0068 M HCl ?
-12
2. How many mL of 0.035 M NaOH are needed to neutralize 45 mL of 0.068 M HCl ? (NaOH is a strong base. HCl is a strong acid)
87. 4 mL
3. How many mL of 0.003 M NaOH are needed to neutralize
75 mL of 0.068 M HCl ?
1.7 L
4. How many mL of 0.04 M NaOH are needed to neutralize
40 mL of 0.15 M HCl ?
150 mL
5. What are the concentrations of CH
[A -
3
COOH and CH
3
COO - in a
0.65 M acetate buffer solution, which has a pH of 4.24.
The pKa for acetate is 4.76.
] = 0.15 M [HA] = 0.5 M
6. What is the pH of 0.075 M solution of weak acid HA if the Ka is 3.8 × 10 -6 pH = 3.27
7. Which of the following has the lowest pH ? highest pH ?
Explain your reasoning with regard to all three solutions.
0.025 M HCl 0.025 M NaOH lowest
0.025 M CH
3 complete ionization of H +
COOH
Ka = 1.75 × 10 - 5
Explain your reasoning.
0.1 M acetic acid.......Ka = 1.8 × 10 -5 highest
complete ionization of OH
8. Which of the following would have the highest pH ?
0.1 M citric acid........Ka = 3.2 × 10 -7
0.1 M boric acid........Ka = 5.4 × 10 -10
Boric acid has the highest pH.
It has the lowest Ka and the least amount of H + in solution.
-

pH = pKa + log [A
9. What is the pH of a 0.0098 M solution of weak acid HA if the pH = 3.7
Ka for HA is 4.5 × 10 - 6 ?
10. Determine the concentration ratio of conjugate base to acid in a
primary phosphate buffer system.
The pH is 2.40.
The Ka is 7.94 × 10 -3 .
_ ]
[HA]
2 / 1
H
3
PO
4
<=====> H + + H
11. What is the concentration ratio of conjugate base to acid for a secondary phosphate buffer system.
2
PO
4
-
The pH of 6.50.
The Ka of is 1.58 × 10 -7 . pH = pKa + log [A ] the acetate buffer system when........
CH
3
COOH <======> H + + CH
3
H
2
COO
PO
-
4
<=====> H +
[HA]
1 / 2
12. Predict the shift in equilibrium (left or right) for
+ HPO
3
-2 a) a solution of HCl is added to the beaker___left_______ b) sodium acetate (NaCH
3
CO
2
) salt is added to the beaker___left_______ c) sodium hydroxide (NaOH) is added to the beaker__right__________
13. At a veterinarian research clinic, dialysis tubing was used to separate sugars from the blood of a cow. Salt ions from the cow's blood also diffused through the tubing. The diffusion of salt ions caused the dialyzate (resulting solution) to become more basic than the cow's blood. As a result the structure and integrity of the sugar molecules was changed. Choose the buffer system that would best preserve the structure of the sugar molecules in the dialyzate. Explain your reasoning.
 distilled water pK w
= 14 , pH = 7.0
 buffer #1 pKa = 7.3, pH = 7.0
 buffer #2 pKa = 7.3, pH = 8.0
You want to buffer against adding a base. A solution with a pH below the pKa will provide this environment.

14. Which of the following is not a property of water ? a. strong hydrogen bonding in liquid b. high molar heat of vaporization ( Δ H vap) c. strong cohesion d. solid state denser than liquid state e. high molar heat of fusion ( Δ H fus)
15. If a solution is at a pH = 10. What is the concentration of hydroxide ions?
a. 10 M b. 4 M c. 10 - 10 M d. 10 - 4 M e. 10 - 7 M
16. The pH of 10 mL of lemon juice is measured in the lab with a pH meter to be 2.3. When 1 mL of a solution is added to the lemon juice and stirred, the new pH of the solution is 4.3. How much did the concentration of hydroxide change ? a. it increased by 50 % (0.5 x) b. it increased by 100 % (1 x) c. it increased by 10,000 % (100 x) d. it decreased by 50 % (-0.5 x) e. it decreased by 100 % (-1 x)
17. The molecular weight of glucose is 180 grams /mol. How much glucose does it take to produce 5 L of 0.2 M solution ? a. 1.8 g b. 3.6 g c. 18 g d. 36 g e. 180 g