(Fall 2025) Equilibrium

Le Chatelier's Principle

100

According to Le Chatelier's Principle, if you add more reactants to a system at equilibrium, what direction will the reaction shift?. what is Q in comparison to K?

the right. Q<K

200

For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing the pressure favors the formation of what side of the equation? answer with Q vs K as well.

Products. to the right. Q<K

300

At a certain temperature, Kc=4.0 for the reaction:

H₂(g)+I₂(g)⇌2HI(g)

If [H₂]=0.20 M, [I₂]=0.10 M, and [HI]=0.30 M,
determine Qc and predict which way the reaction will shift to reach equilibrium.

Qc=4.5

Qc>K. Shift Left

400

In the reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) + heat, explain how the equilibrium position changes when both temperature and pressure are increased.

It shifts toward the products because of higher pressure (fewer gas moles), but back toward the reactants because adding heat favors the endothermic reverse reaction.

500

For the equilibrium

CO(g)+H₂O(g)⇌CO₂(g)+H₂(g)

Kc=1.6×10^-2 at a given temperature.
A mixture has: [CO]=0.020 M, [H₂O]=0.040 M, [CO₂]=0.050 M, and [H₂]=0.050M.

Is the reaction in equilibrium? If not, what direction should it shift?

Q=3.125

Q>K

not in equilibrium

shift left

RICE Tables

100

For the reaction

H₂(g)+I₂(g)⇌2HI(g)

Initially, [H₂]=[I₂]=1.00 M and [HI]=0.
At equilibrium, [HI]=1.60 M.
Find Kc

Kc=64

200

N₂O₄(g)⇌2NO₂(g)

Kc=0.25
If initially, [N₂O₄]=0.10 M and [NO₂]=0.00 M, find the equilibrium concentrations.

[N₂O₄] = 0.04625 M and [NO₂] = 0.1075 M

300

At 700K, Kc=54.3 for

H₂(g)+CO₂(g)⇌H₂O(g)+CO(g)

Initial concentrations: all 0.10 M.
Predict the shift and calculate equilibrium concentrations.

shift right

[H₂]=[CO₂]=0.10−0.076≈0.024M

[H₂O]=[CO]=0.10+0.076≈0.176M

400

Consider the reaction 

CO(g)+2H₂(g)<-->CH₃OH(g)

 A reaction mixture in a 1.00L flask initially only contains 0.185 mol CO and 0.225 mol H2. At equilibrium, 0.0521 mol CH3OH have formed. Calculate the equilibrium constant Keq for this reaction.

26.86

500

Consider the reaction 

PbCl₂(s)<-->Pb²⁺(aq)+2Cl^-(aq) 

with Ksp = 1.17x10^-5. Determine the equilibrium CONCENTRATION of Pb²⁺ and Cl^- if you dissolve PbCl₂ in a 0.100M solution of NaCl.

1.17x10^-3M

Random Poo

100

In human anatomy, the "hallux" refers to this body part. 

what is the big toe

200

The more you take from me, the bigger I get. 

What is a hole?

300

The US President who famously said "Mr. Gorbachev, tear down this wall."

Who is Ronald Reagan?

400

In 1920, the ratification of this amendment finally granted women's suffrage. 

What is the 19th Amendment?

500

Although this enzyme catalyzes an irreversible step in glycolysis, it is allosterically inhibited by ATP and citrate, allowing coordination between glycolysis and the citric acid cycle. 

What is phosphofructokinase-1 (PFK-1)?

Keq Expressions

100

H₂(g)+Cl₂(g)⇌2HCl(g)

Write the Kc expression.

Kc = [HCl]²/[H₂][Cl₂]

200

N₂(g)+3H₂(g)⇌2NH₃(g)

Write both Kc and Kp expressions.

Kc = [NH₃]/[N₂][H₂]³

Kp = same thing but with "P"

300

Write the corresponding reaction for the following Ksp expression

Ksp=1/[Pb²⁺][Cl^-]

:)

400

1. H₂(g)+I₂(g)⇌2HI(g), K1=50

2. 2HI(g)⇌H₂(g)+I₂(g), K2=?

reverse reaction 1 to get reaction 2. 

do reciprical of K1 

K2 = 1/50

500

Target reaction:

C(s)+CO₂(g)⇌2CO(g)

Given reactions:

1. CO₂(g)⇌CO(g)+ 1/2 O₂(g), K1=1.2×10⁻⁵

2. C(s)+O₂(g)⇌CO₂(g), K2=8.0×10⁷

Calculate K_target

K_target=0.01152

Equilibrium & Thermodynamics

100

For the reaction:

N₂O₄(g)⇌2NO₂(g)

At 298 K, ΔG^∘=4.00 kJ/mol

Initial concentrations: [N₂O₄]=0.50 M,[NO₂]=0.50 M

R=8.314×10⁻³ kJ/molK

1. Calculate K at 298 K.

2. Calculate Q for the given concentrations.

3. Determine if the reaction is spontaneous in the forward or reverse direction.

K=0.199

Q=0.5

Shift left

200

The reaction:

H₂(g)+I₂(g)⇌2HI(g)

has ΔG^∘=2.5 kJ/mol at 700 K.

Initial concentrations: [H₂]=0.10M, [I₂]=0.10M, [HI]=0.50 M

• Calculate K.

• Calculate Q.

• Predict the direction the reaction will shift to reach equilibrium.

K=0.65

Q=25

shift left

300

CO(g)+H₂O(g)⇌CO₂(g)+H₂(g)

ΔG^∘=−28.6 kJ/mol at 1000 K

Initial pressures: P_CO=0.50 atm, P_H2O=1.0 atm, P_CO2=0.20 atm, P_H2=0.20 atm

Calculate ΔG under these nonstandard conditions and determine if the reaction is spontaneous.

-49.6kJ/mol

400

2NO(g)+O₂(g)⇌2NO₂(g)

• ΔG^∘=−72.4 kJ/mol at 500 K

• Current pressures: P(NO)=0.10 atm,P(O₂)=0.25 atm,P(NO₂)=0.05 atm

1. Calculate Q.

2. Calculate ΔG at 500 K.

3. Predict the direction of spontaneous reaction.

Q=1

ΔG=-72.4kJ/mol

It is spontaneous going forward (the reaction is not in equilibrium because ΔG must equal zero. This answer is less than zero)

500

N₂(g)+3H₂(g)⇌2NH₃(g)

ΔG^∘=−16.4 kJ/mol at 298 K

Current pressures: P(N₂)=1.0 atm,P(H₂)=2.0 atm,P(NH₃)=0.1 atm

1. Calculate K at 298 K.

2. Calculate Q.

3. Determine ΔG at these nonstandard pressures.

4. Predict which direction the reaction will shift.

K=749.5

Q=0.00125

ΔG=-32.96kJ/mol

shift right (Q<K)