2B Chemical Equilibrium

Question 1

1. What is an equilibrium
2. What is a physical equilibrium (w/ an example)
3. What is a chemical equilibrium

Answer 1

1. Occurs when two competing processes balance
2. Balance between two competing processes (phase transitions)
3. Reactants and products are chemicals different but forward and backward reaction occur at same rate

Question 2

1. A chemical equilibrium is not achieved ______
2. At equilbrium, what happens to concentrations and reactions

Answer 2

1. Instantaneously
2. Concentrations stop changing but reactions do not stop

Question 3

What is Kc called and how do you find the Kc of a reaction that involves aA + bB _> cC + dD

Answer 3

1. Kc is the equilibrium constant
2. Kc=[C]^c [D]^d / [A]^a [B]^b

Question 4

Why does Kc not have units?

Answer 4

The correct quantities that enter Kc are the activities so they are dimensionless. Assume units are implicit and not write them out.

Question 5

1. How do the forward and reverse rates related at equilibrim
2. What Kc a ratio of

Answer 5

1. Forward rate= reverse rate
2. Ratio of forward and reverse rate constants, which is a constant at equilibrium

Question 6

If Kc is&raquo_space;» 1, what side does it lie and does it favor products/reactants

Answer 6

Lies on the Right, favors products

Question 7

If Kc is «&laquo_space;1, what side does it lie and does it favor products/reactants

Answer 7

Lies to the left, favors reactants

Question 8

Homogenous equilbrium

Answer 8

Applies to reactions in which all reacting species are in the same phase

Question 9

How do you determine the equilibrium constant for a homogenous equilibria of gases. How do you find this in respect to Kc

Answer 9

Kp is based on partial pressures instead of concentrations
Kp=Kc(RT)^dn
Dn refers to change in moles of products-reactants (ONLY USE gaseous chemicals)

Question 10

Heterogenous equilibrium

Answer 10

Applies to reactions in which reactants and products are in different phases

Question 11

What concentrations are NOT included in the expression for an equilibrium constant

Answer 11

Solids and Pure liquids

Question 12

WHat is the ion product constant (Kw)

Answer 12

The product of the molar concentrations of H+ and Oh- at a particular temperature
Kw=[H+][OH-]

Question 13

1. Neutral
2. Acidic
3. Basic

Answer 13

The solution is:
1. [H+]=[OH-]
2. [H+]>[OH-]
3. [H+]<[OH-]

Question 14

1. What is Ka
2. When is it small and when is it large
3. [H2O] is generally ______ in the equilibrium constant when it is a _____

Answer 14

1. Ka is called the acid ionization constant
2. Ka is small for weak acids, large for strong acids
3. Not included;solvent

Question 15

How do you find the equilibrium constant if the reversible reaction is written in opposite direction

Answer 15

Take the reciprical of the original constant