Homework1 2015 Key
Homework 1_Key
BCH2333 Winter 2015
Topics covered: review, Chemical Evolution, Water, Non-covalent bonds, Acid/base, pH
1.
i) Convert using scientific notation to liters: 4 nanoliters, 4 x 10-9 L, 20 microliters, 2x10-5 L, 35 milliliters, 3.5 x 10-2 L, 10 deciliters, 1 L, 7 kiloliters 7 x 103 L ii) Convert using scientific notation to grams: 6 mg, 6 x 10-3 g, 21 µg, 2.1 x 10-5 g,
503 ng, 5.03 x 10-7 g, 10 kg, 1 x 104 g
2. Which of the following properties of water explains its ability to dissolve acetic acid?
(there may be more than one correct answer)
a. The high surface tension of water, which is due to the formation of hydrogen bonds between adjacent water molecules.
b. The ability to serve as a buffer, absorbing protons given off by acetic acid.
c. The ability to orient water molecules so that their polarities neutralize the ions formed when the acid dissociates.
d. The ability to form hydrogen bonds with the carbonyl and the hydroxyl groups of acetic acid.
3. The pH of a solution is equal to:
a.
b.
c.
d.
e.
the hydrogen ion concentration H+ log [H+]
-log[H+]
ln[H+]
-ln[H+]
4. Physiological pH is 7.4. What is the hydrogen ion concentration of a solution at physiological pH?
a.
b.
c.
d.
e.
-7.4 M
0.6 M
0.6 X 10-8 M
1 X 10-8 M
4 X 10-8 M
5. What is the pH of a 10-3 M solution of HCl?
pH = 3
6. What is the pH of a 10-10 M solution of HCl? Why? pH = 7. Pure water has 10-7 M
H+. The H+ from 10-10 M HCl will not appreciably increase the concentration of H+ therefore the pH = 7.
7. If the concentration of H+ in a solution is 10 - 3 M, what will the concentration of OH be in the same solution at 25° C? [OH-] = 10-11 M from (Kw= [H+][OH-])
Homework 1_Key
BCH2333 Winter 2015
8. How many mL of a 0.4 M HCl solution are required to bring the pH of 10 mL of a 0.4
M NaOH solution to pH 7.0 (neutral pH)?
Note: HCl and NaOH both completely dissociate in water (i.e., no pKa calculation is necessary). 10 mL Have 4 mmol total of OH- therefore you need to add 4 mmol
BCH2333 Winter 2015
Topics covered: review, Chemical Evolution, Water, Non-covalent bonds, Acid/base, pH
1.
i) Convert using scientific notation to liters: 4 nanoliters, 4 x 10-9 L, 20 microliters, 2x10-5 L, 35 milliliters, 3.5 x 10-2 L, 10 deciliters, 1 L, 7 kiloliters 7 x 103 L ii) Convert using scientific notation to grams: 6 mg, 6 x 10-3 g, 21 µg, 2.1 x 10-5 g,
503 ng, 5.03 x 10-7 g, 10 kg, 1 x 104 g
2. Which of the following properties of water explains its ability to dissolve acetic acid?
(there may be more than one correct answer)
a. The high surface tension of water, which is due to the formation of hydrogen bonds between adjacent water molecules.
b. The ability to serve as a buffer, absorbing protons given off by acetic acid.
c. The ability to orient water molecules so that their polarities neutralize the ions formed when the acid dissociates.
d. The ability to form hydrogen bonds with the carbonyl and the hydroxyl groups of acetic acid.
3. The pH of a solution is equal to:
a.
b.
c.
d.
e.
the hydrogen ion concentration H+ log [H+]
-log[H+]
ln[H+]
-ln[H+]
4. Physiological pH is 7.4. What is the hydrogen ion concentration of a solution at physiological pH?
a.
b.
c.
d.
e.
-7.4 M
0.6 M
0.6 X 10-8 M
1 X 10-8 M
4 X 10-8 M
5. What is the pH of a 10-3 M solution of HCl?
pH = 3
6. What is the pH of a 10-10 M solution of HCl? Why? pH = 7. Pure water has 10-7 M
H+. The H+ from 10-10 M HCl will not appreciably increase the concentration of H+ therefore the pH = 7.
7. If the concentration of H+ in a solution is 10 - 3 M, what will the concentration of OH be in the same solution at 25° C? [OH-] = 10-11 M from (Kw= [H+][OH-])
Homework 1_Key
BCH2333 Winter 2015
8. How many mL of a 0.4 M HCl solution are required to bring the pH of 10 mL of a 0.4
M NaOH solution to pH 7.0 (neutral pH)?
Note: HCl and NaOH both completely dissociate in water (i.e., no pKa calculation is necessary). 10 mL Have 4 mmol total of OH- therefore you need to add 4 mmol