CHm

Question 1

What does equilibrium mean in a chemical process?

Answer 1

At equilibrium, the forward rate and reverse rate are equal.

Question 2

How do you write the expression for the equilibrium constant (K)?

Answer 2

K = [products]^m / [reactants]^n

Example: K = [C]^c [D]^d / [A]^a [B]^b

Question 3

What does it mean if K > 1?

Answer 3

If K > 1, the equilibrium is product favored.

Question 4

What does it mean if K < 1?

Answer 4

If K < 1, the equilibrium is reactant favored.

Question 5

What is the relationship of K for a forward reaction and K for the reverse reaction?

Answer 5

K for a forward reaction = 1 / K for the reverse reaction.

Question 6

How is a solid or pure liquid treated in the equilibrium constant expression?

Answer 6

It is assigned a value of 1 and left out of the equilibrium constant expression.

Question 7

How do you use an ICE Table?

Answer 7

An ICE Table helps determine the value for K or equilibrium concentrations.

Question 8

How do you determine the value for Q?

Answer 8

If Q > K, the equilibrium will shift to the left. If Q < K, the equilibrium will shift to the right.

Question 9

What is Le Châtelier’s Principle?

Answer 9

It describes how various stresses affect the equilibrium of a reaction.

Question 10

What is the Arrhenius definition of an acid?

Answer 10

An acid produces H+ ion in water solution.

Question 11

What is the Arrhenius definition of a base?

Answer 11

A base produces OH– ion in water solution.

Question 12

What do an acid and a base produce when they react?

Answer 12

An acid + a base will produce water + a salt.

Example: HBr + KOH → H2O + KBr

Question 13

What is the net ionic equation of an acid-base reaction?

Answer 13

H+ + OH– → H2O.

Question 14

What is the Brønsted-Lowry definition of an acid?

Answer 14

An acid is a proton (H+) donor.

Question 15

What is the Brønsted-Lowry definition of a base?

Answer 15

A base is a proton (H+) acceptor.

Question 16

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

Answer 16

A strong acid ionizes at 100%, while a weak acid only ionizes a small part.

Question 17

What are the names of these ions: H+, OH–, H3O+?

Answer 17

H+ is the hydrogen ion, OH– is the hydroxide ion, and H3O+ is the hydronium ion.

Question 18

What are the 6 strong acids?

Answer 18

HCl, HBr, HI, HNO3, H2SO4, HClO4.

Question 19

Which hydroxides are considered strong bases?

Answer 19

LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, Ba(OH)2.

Question 20

What happens when an acid loses a proton?

Answer 20

It becomes its conjugate base.

Question 21

What happens when a base gains a proton?

Answer 21

It becomes its conjugate acid.

Question 22

What is the conjugate base of the weak acid HA?

Answer 22

A–.

Question 23

What is the reaction of a weak acid with water?

Answer 23

HA + H2O ⇌ H3O+ + A–

acid + base ⇌ conj. acid + conj. base

Question 24

How do you calculate [H+], [OH–], pH, and pOH of strong acids or bases?

Answer 24

[HA] = [H3O+] for strong acids; [BOH] = [OH–] for strong bases.

pH = -log[H3O+]; pOH = -log[OH–]; [H+] = 10^(-pH); [OH–] = 10^(-pOH).

Question 25

What is the algebraic expression for Ka of a weak acid?

Answer 25

Ka = [H3O+][A–] / [HA].

Question 26

What is the value of Kw at 25°C?

Answer 26

Kw = [H3O+][OH–] = 1.0 x 10^-14.

Question 27

What is 'The Common Ion Effect'?

Answer 27

Adding the negative ion of an acid will result in lesser ionization of the acid.

Question 28

What components are necessary for a buffered system?

Answer 28

A weak acid and its conjugate base.

Question 29

What is the function of a buffered system?

Answer 29

To maintain the pH, even if small quantities of a strong acid or base are added.

Question 30

What is the Henderson-Hasselbalch equation?

Answer 30

pH = pKa + log[base]/[acid]. ## Footnote It is used to find the pH of a buffered system.

Question 31

What is a perfect buffer?

Answer 31

When [acid] = [base].

Question 32

How do you determine the pH of a perfect buffer?

Answer 32

pH = pKa.

Question 33

How do you select an acid for a buffer at a certain pH?

Answer 33

Select an acid with a pKa close to the desired pH.

Question 34

How do you determine the ratio of an acid and its conjugate base for a buffer?

Answer 34

Substitute known values for pH and pKa, and solve for [base]/[acid].

Question 35

What are 'system' and 'surroundings' in thermodynamics?

Answer 35

The system is the material in the reaction; the surroundings are everything else.

Question 36

What is enthalpy?

Answer 36

The heat energy lost or gained in a reaction.

Question 37

What is the sign of ΔH for endothermic and exothermic reactions?

Answer 37

Endothermic ΔH is positive; exothermic ΔH is negative.

Question 38

How does ΔH for a forward reaction compare to ΔH for the reverse reaction?

Answer 38

ΔH forward = -ΔH reverse.

Question 39

What is specific heat?

Answer 39

Specific heat is the amount of heat required to change the temperature of a substance.

Question 40

What is entropy?

Answer 40

A measure of the degree of randomness or disorder of a system.

Question 41

What is Gibbs Free Energy?

Answer 41

The energy associated with a chemical reaction that can be used to do work.

Question 42

What is the relationship between ∆Go, ΔHo, and ∆So?

Answer 42

∆Go = ΔHo - T∆So.

Question 43

How do you determine if a reaction is spontaneous?

Answer 43

Use the signs of ΔHo and ΔSo to determine the sign of ∆Go.

Question 44

What is the relationship between ∆Go and K in a spontaneous reaction?

Answer 44

If a reaction is spontaneous, ∆G° will be negative and K will be greater than 1.