Download Chemistry Wksht 26

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Worksheet
1. A solution of an electrolyte will conduct
electricity, because it forms ions in water.
A nonelectrolyte does not conduct electricity
when it is dissolved in water.
2. Any salt, acid or base is considered an
electrolyte, NaCl and HCl. Any covalent
molecule other than acids are nonelectrolytes,
CH4 and N2O5 are examples.
3. A strong electrolyte ionizes or dissociates into
ions 100%. A weak electrolyte forms ions in
water, but it does not ionize 100%.
4. Any salt is a strong electrolyte, KNO3 and
MgSO4. Weak acids and bases are weak
electrolytes, HF and HClO are examples.
KA8526
5. Water self ionizes to a very small extent, so
the observation that water conducts electricity
is the result of dissolved minerals that
produce ions.
The Self-Ionization of
Water
6. H2O → H+ + OH-.
→
Lesson Twenty Six
7. Kw = [H+][OH-] = 1 x 10-14, H2O is not
included because it is a pure liquid.
8. [H+] = [OH-] = 1 x 10-7 M.
The Complete Course
9. pH = 7.
CHEMISTRY
10.1 x 10-14 M.
ANSWERS
I. VIDEOTAPE FOLLOW-UP QUESTIONS
I. One of the most important equilibria that
exists in nature is the equilibrium that exists in
water; this is referred to as the self-ionization
of water.
A.Substances that are liquids or that dissolve
in water are often divided into three broad
categories.
1. These categories are called
nonelectrolytes, strong electrolytes, and
weak electrolytes.
a. Nonelectrolytes do not conduct
electricity.
b. Strong electrolytes conduct electricity
very well.
c. Weak electrolytes conduct electricity
to a small extent.
d. The key to whether a substance
conducts electricity and how well it
conducts electricity is whether or not
it forms ions in solution.
e. Nonelectrolytes are made of
molecules and remain molecules
when dissolved in water.
f. Strong electrolytes exist in water only
as ions.
g. Weak electrolytes dissolve in water to
form mostly molecules, but with a
small percentage of the molecules
being broken apart to form ions.
2. Water is classified as a weak electrolyte.
B. The self-ionization of water can be
represented by the equation
H2O(l) <---> H+(aq) + OH-(aq).
1. The equilibrium constant for this reaction
is called the ion product of water.
a. It is represented by the symbol Kw.
b. Kw = [H+][OH-] = 1.00 x 10-14 at 25°C.
2. If the concentration of hydrogen ion in
an aqueous solution is high, the
concentration of hydroxide ion must be
low, and vice-versa.
II. Several problems related to the ion product of
water are presented and solved.
III. The pH of a solution is defined as -log[H+].
A.The pH of an acidic solution is less than
seven, the pH of a neutral solution is equal
to seven, and the pH of a basic solution is
greater than seven.
B. The logarithm of a number is the power to
which 10 must be raised to obtain the
number.
C. The discussion of pH will be continued in
Lecture #27.
II. SUPPLEMENTARY EXERCISES
1. What is the difference between an
electrolyte and a nonelectrolyte?
2. Give two examples each of an electrolyte
and a nonelectrolyte.
3. What is the difference between a strong
electrolyte and a weak electrolyte?
4. Give two examples each of a strong
electrolyte and a weak electrolyte.
5. Why does water conduct electricity?
6. Write the equation for the self ionization
of water.
7. What is the equilibrium constant expression
for water? Why is the H2O excluded?
8. If the KW is 1 x 10-14, what is the [H+] and
[OH-] in pure, deionized water?
9. What is the pH of a sample of pure,
deionized water?
10. If the [H+] is 1.0 M, what is the [OH-] in
the same sample?