Le Chatelier's Principle #1
When products are added to a system at equilibrium, which direction would equilibrium shift to?
Shifts to left.
Favors reactants.
N2 + 3 H2 ⇌ 2 NH3 ΔH = - 92kJ/mol
Which direction would equilibrium shift when a catalyst is successfully added.
No change/shift.
** Catalysts speed reactions, but don't make more of anything.
An equilibrium mixture is analyzed and found to contain 0.62M N2, 0.50M H2, and 0.24M NH3. What is Kc for the reaction, N2(g) + 3H2(g) ⇌ 2NH3(g)
Kc= 0.74
Which statement concerning a chemical reaction at equilibrium is not correct?
A. The concentrations of reactants and products remain constant.
B. Equilibrium can be approached from both directions.
C. The rate of the forward reaction equals the rate of the reverse reaction.
D. All reaction stops.
D. All reaction stops.
All questions are based on this problem:
Ammonia gas (NH3) is produced in industrial amounts for the production of fertilizers. The most well-known industral process for this is the Haber-Bosch Process.
N2 + H2 <--> NH3
The equilibrium constant for this process is 0.496. A 5.00L reaction vessel is set up with 20.0 mol of N2; and 75.0 mol of H2.
33.0 mol of NH3 will be made at equilibrium.
What are the initial concentrations of both reactants?
[N2] = 4.00M
[H2] = 15.0M
When reactants are removed from a system at equilibrium, which direction would equilibrium shift to?
Shifts to the left
Favors reactants
N2 + 3 H2 ⇌ 2 NH3
An increase in pressure would cause the reaction to shift in which direction?
Right (Fewer moles)
What is the equilibrium constant equation of this reaction?
SnO2 (s) + 2 CO (g) ⇌ Sn (s) + 2 CO2(g)
[CO2]2
[CO]2
Why do we refer to chemical equilibrium as "dynamic"?
Reaction continues, even if the concentrations stay the same.
Set up the ICE table needed to find the concentration of each compound at equilibrium.
N2 3H2 <--> 2NH3
I 4.00M 15.0M 0M
C -x -3x +2x
E 4.00-x 15.0-3x 0+2x
What will happen to the position of equilibrium of this reaction was put under less pressure?
Br2 (g) + Cl2 (g) ⇌ 2 BrCl(g)
∆H = +14 kJ/mol
No change (equal number of moles)
If a reaction is shifted to the right, what change would that cause to the equilibrium constant?
Value would increase
Which statement(s) is/are true for a mixture of ice and liquid water at equilibrium?
I. The rates of melting and freezing are equal.
II. The amounts of ice and water are equal.
III. The equilibrium can be reached by cooling water and heating ice.
I. The rates of melting and freezing are equal.
III. The equilibrium can be reached by cooling water and heating ice.
What is the equilibrium constant expression for the following reaction?
I2 (g) + 3 Cl2 (g) ⇌ 2 ICl3 (g)
[ICl3]2
[I2][Cl2]3
Use the equilibrium Concentration of NH3 (33.0 mol in 5.00L) to find the Equilibrium (End) concentrations of both the N2 and H2 (you might not need to use quadratic equation)
x = 3.3M
[H2] = 5.1M at equilibrium
[N2] = 0.7M at equilibrium
N2 + 3 H2 ⇌ 2 NH3
ΔH = -92kJ/mol
Which direction would equilibrium shift to when heat is added?
Left (Higher energy side)
Which of the following equilibria would not be affected by pressure changes at constant temperature?
A. 4 HCl(g) + O2(g) ⇌ 2 H2O(g) + 2 Cl2(g)
B. CO(g) + H2O(g) ⇌ H2(g) + CO2(g)
C. C2H4(g) + H2O(g) ⇌ C2H5OH(g)
D. PF3Cl2(g) ⇌ PF3(g) + Cl2(g)
B. CO(g) + H2O(g) ⇌ H2(g) + CO2(g)
At a given temperature, an equilibrium mixture of the reaction 2 NO(g) + O2(g) <--> 2 NO2(g) contains 0.090 moles NO, 0.120 moles of O2, and 0.060 moles of NO2 in a 3.00 liter container.
The value of Kc is...
Kc= 11
NH4SH (s) ⇌ NH3 (g) + H2S (g) Write the equilibrium expression.
What is Kc = [NH3] [H2S]
**Solids not included in equilibrium expression
Find the Kc of this equation now that you know the equilibrium concentrations
Kc = 0.469 (3 significant figures)
2 SO2(g) + O2 (g) ⇌ 2 SO3(g) ∆H = –200 kJ
According to the above information, what temperature and pressure conditions produce the greatest amount of SO3?
(High vs low for both temperature and pressure)
Temperature: Low
Pressure: High
The equation for a reaction used in the manufacture of nitric acid is
4 NH3 (g) + 5O2 (g) ⇌ 4NO (g) + 6H2O (g)
∆H = –900 kJ /mol
What changes would happen to the position of equilibrium AND the value of Kc when the temperature of the reaction is increased?
Shifts left.
Value of Kc decreases.
Kc for the equilibrium reaction is determined at two different temperatures.
At 850°C, Kc = 1.1.
At 1700°C, Kc = 4.9.
Based on these values, is this reaction likely to be exothermic or endothermic.
Endothermic
(Higher temperature led to more products)
0.0206 M CH3OH, 0.120 M carbon monoxide, and 0.282 M hydrogen at 500 K. Calculate the equilibrium constant at this temperature.
CO (g) + H2 (g) ⇌ CH3OH (g)
Does this favor the reactants or the products?
Products (Kc = 2.16)