Chem 162 (Chapters 15 + 16)

Question 1

What is the equation for the equilibrium constant Keq of this chemical equation.

N_2(g)+O_2(g)⇔2NO_(g)

Answer 1

K = [NO]²/[N₂][O₂]

Question 2

What does it mean to be in dynamic equilibrium?

Answer 2

The rates of the forward and reverse reactions are the same.

The concentrations (or any other values) are not necessarily equal.

Question 3

When the equilibrium constant K is 2.1·10^-20, what can be said about this reaction?

a) At equilibrium the concentrations of products and reactants are the same.
b) At equilibrium the concentration of products is much greater than that of reactants.
c) At equilibrium the concentration of reactants is much greater than that of products.
d) There are no reactants left over.

Answer 3

c) [reactants] >> [products] at equilibrium

because K is so small

Question 4

In the equilibrium constant equation for heterogeneous equilibria what is omitted?

Answer 4

Concentrations of pure solids and liquids.

Question 5

Given:

2HgO_(s)+H₂O_(l)+2CO_2(g)⇔2HOCl_(aq)+HgO·HgCl_2(s)

What is the equilibrium constant expression for this heterogeneous reaction?

Answer 5

K = [HOCl]²/[CO₂]²

Question 6

Given [OH^-], what is the pOH?

Answer 6

-log[OH^-]

Question 7

Given pH, how would you find [H⁺]

Answer 7

10^-pH

Question 8

Given pOH, how would you find pH?

Answer 8

14-pOH=pH

Question 9

What is H₂SO₄?

Answer 9

Sulfiric Acid

Question 10

What is HNO₃?

Answer 10

Nitric Acid

Question 11

What is HC₂H₃O₂?

Answer 11

Acetic Acid

Question 12

What is the Arrhenius definition of acids and bases?

Answer 12

Acid: Produces H⁺ (H₃O⁺)

Base: Produces OH^-

Question 13

What is the Bronsted-Lowry definition of acids and bases?

Answer 13

Acid: Proton donor.

Base: Proton acceptor.

Question 14

What is the definition of a strong acid?

Answer 14

100% ionization.

Question 15

What is the difference between a strong acid and a weak acid?

Answer 15

Strong acids completely dissociate in water whereas weak acids only partially dissociate.

Question 16

What are the six important strong acids?

Answer 16

HCl (Hydrochloric Acid)

HBr (Hydrobromic Acid)

HI (Hydriodic Acid)

HNO₃ (Nitric Acid)

HClO₄ (Perchloric Acid)

H₂SO₄ (Sulfuric Acid)

Question 17

What is a diprotic acid?

Answer 17

An acid containing two ionizable atoms.

Question 18

Of the six important strong acids, which is diprotic?

Answer 18

H₂SO₄ (Sulfuric Acid)

-because of the two hydrogens

Question 19

Name at least 3 of the main weak acids.

Answer 19

1) HF (Hydrofluoric Acid)
2) HC₂H₃O₂(Acetic Acid)
3) HCHO₂ (Formic Acid)
4) H₂SO₃ (Sulfurous Acid)
5) H₂CO₃(Carbonic Acid)
6) H₃PO₄(Phosphoric Acid)

Question 20

Given:

HA_(aq) ⇔ H⁺_(aq) + A^-_(aq)

What is the K_a of this reaction?

Answer 20

K_a={[H⁺][A^-]}/[HA]

Question 21

Is water an acid or a base?

Answer 21

It can act as either one.

Question 22

What is K_w and what is its value at 25^oC?

Answer 22

K_wis the ion product constant for water.

At 25^oC, K_w=1.0x10^-14

Question 23

How do you calculate percent ionizaton?

Answer 23

%ion. = ^{conc of ionized acid}/_{initial conc of acid}

Question 24

What is a strong base?

Answer 24

A base that completely dissociates in water.

Question 25

Name at least 3 of the main strong bases.

Answer 25

1. LiOH (Lithium Hydroxide)
2. NaOH (Sodium Hydroxide)
3. KOH (Potassium Hydroxide)
4. Sr(OH)₂ (Strontium Hydroxide)
5. Ca(OH)₂ (Calcium Hydroxide)
6. Ba(OH)₂ (Barium Hydroxide)

Question 26

Given:

B_(aq)+H₂O_(l)⇔BH⁺_(aq)+OH^-_(aq)

What is K_b?

Answer 26

K_b=^[BH+][OH-]/_[B]

Question 27

If an anion is the conjugate base of a weak acid then it is…

Answer 27

…a weak base itself.

Question 28

If an anion is a conjugate base of a strong acid it is…

Answer 28

…pH neutral.

Question 29

What is K_w’s relationship to K_a and K_b?

Answer 29

K_w=K_aK_b

Question 30

A cation that is the conjugate acid of a weak base…

Answer 30

…is a weak acid.

Question 31

Salts in which the cation does not act like an acid and the anion acts like a base form…

Answer 31

…basic solutions.

Question 32

Salts in which the cation acts as an acid and the anion does not act like a base form…

Answer 32

…acidic solutions.

Question 33

How do polyprotic acids dissociate?

Answer 33

In several successive steps.

Each has its own K_a.

Question 34

What equation relates pH to pK_a?

Question 35

What does a buffer do?

Answer 35

Resists pH change by neutralizing added acids or bases.

Question 36

When an acid is added to a buffer, a stoichiometric amount of the [ ] is converted to the [ ].

Question 37

When a base is added to a buffer, a stoichiometric amount of the [ ] is converted to the [ ].

Question 38

pK_a+pK_b=?

(numerical value)

Answer 38

14

Question 39

What is the relation between [H₃O⁺], [OH^-] and K_w?

Answer 39

K_w=[H₃O⁺] [OH^-]

Question 40

When can some ions behave like acids or bases?

Answer 40

In an aqueous solution.

Question 41

What is required for a buffer solution?

Answer 41

A weak acid and its conjugate base or a weak base and its conjugate acid.

Question 43

What are Lewis acids and bases?

Answer 43

Lewis acid: electron pair acceptor

Lewis base: electron pair donor