Le Chatelier's Principle
What is Le Chatelier's Principle?
A system will respond to change in order to minimize change
What is the variable for entropy?
ΔS
What is equilibrium?
How do you solve for K?
Use 2A+3B2 --> 2AB3 to explain your answer
(AB3)2/ ((A)2 x (B2)3)
When is the reaction spontaneous in terms of ΔG?
Does it require an input of energy?
When ΔG is negative
Nope
If volume decreases, what happens to pressure?
Which way would a reaction go?
Pressure increases
To the side with less moles
What is entropy?
Tendency for energy/matter to disperse to arrangements that maximize the number of possible states
We can solve for Q in order to determine what?
Find the temporary state of the reaction and determine reaction direction
Initially, 1.0 mol of NO(g) and 1 mol of Cl2(g) were added to a 1 L container. As a result of the reaction the equilibrium concentration of NOCl(g) became 0.96 M.
K= 1.11 x 103
How would you determine if enthalpy or entropy is driving spontaneity?
The number that ultimately causes ΔG to be negative
What happens if you add more product?
It shifts towards the reactants
When ΔH is negative and ΔS is positive, what is true about spontaneity?
If K is larger than Q, what direction would the reaction proceed?
Forward
2 NO (g) + 2 H2 (g) --> N2 (g) + 2 H2O (g) Determine the value of the equilibrium constant for the reaction. Initially, a mixture of 0.100 M NO, 0.050 M H2, 0.100 M H2O was allowed to reach equilibrium (initially there was no N2). At equilibrium the concentration of NO was found to be 0.062 M.
K= 6.5 x 102
For a certain chemical reaction:
change in free energy (ΔG°): -40.7 kJ
enthalpy change (ΔH°): -23.5 kJ
temperature (T): 523 K
What is the entropy change (ΔS°) in J/K?
32.9
What happens if a reaction is endothermic and temperature is increased?
It shifts towards the products
What is happening to the entropy of the universe?
It is always increasing
What is the K constant for the below reaction at equilibrium that has concentrations:
[SO2] = 3.0 x 10-3 [O2] = 3.5 x 10-3
[SO3] = 5.0 x 10-2
2 SO2 + O2 ⇄ 2 SO3
7.9 x 104
Here is a general reaction with a K value of 2.8x10-7: A (aq) + B (aq) ↔ 2C(aq) Initially you are given 4M of substance A and 4M of substance B. What is x?
x= 1.06 x 10-3
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
Substance ΔGf°
hydrochloric acid (HCl) -131.2 kJ/mol
sodium chloride (NaCl) -393.2 kJ/mol
sodium hydroxide (NaOH) -419.2 kJ/mol
water -237.1 kJ/mol
What is the change in free energy (ΔG°) in kJ?
-79.9 kJ
What happens if a reaction is exothermic and the temperature is decreased?
It would shift towards products
Is entropy increasing or decreasing?
a. increasing
b. decreasing
c. increasing
What is the equilibrium K of a reaction at 350 K with a ΔG = 4 kJ/mol?
R=8.314 J/K
0.253 kJ/mol
What are the equilibrium concentrations for the following reaction:
Cl2 --> 2 Cl K= 1.13 x 10-4 where initial concentrations are [Cl2]= 0.500 and [Cl] = O
x=0.00370
[Cl2]= 0.5 M
[Cl]= 7.52 x 10-3 M
Calculate K for the reaction of O2 with N2 to give NO at 423 K:
N2(g)+O2(g)⇌2NO(g)
ΔG° for this reaction is +22.7 kJ/mol of N2.
R=8.314 J/K
K=1.6×10−3