Equilibria Flashcards
State Le Chatelier’s principle
when a change is imposed on an equilibrium, the equilibrium position will shift to oppose the change
Define dynamic equilibrium
The rate of reaction of the forward and backward reactions are equal
Concentrations of the reactant and products remain constant
What happens to the position of equilibrium if temperature is increased?
Equilibrium shifts in the endothermic reaction to oppose the change (absorbing heat to reduce temperature)
If the position of equilibrium moves in the exothermic direction, what has happened to the temperature?
The equilibrium position moves to opposite the change (by generating heat energy), hence temperature has decreased
What will happen to the position of equilibrium if pressure is increased (in gaseous system)?
Equilibrium will shift in the direction with the fewer moles of gas to oppose (reducing the pressure)
In the production of ammonia from nitrogen and hydrogen, does high or low pressure increase the yield?
High pressure (N₂ + 3H₂ →2NH₃)
The equilibrium moves to the right, with fewer gas molecules, to oppose the change)
What effect does a catalyst have on the equilibrium position?
NONE
Speeds up the rate of the forward and backward reactions equally
I₂ + 2OH⁻ ⇌ I⁻ + IO⁻ + H₂O
What will be the effect if increasing the concentration of OH⁻ ions?
The position of equilibrium will shift to oppose the change (remove OH⁻ ions) and will move to the right.
Why are the temperature and pressure used in the Haber process (N₂+3H₂⇌2NH₃) considered to be a compromise?
High pressure / low temperature move equilibrium to right.
High pressures are expensive (special equipment needed to handle safely)
Low temperatures slow the reaction rate
What is the equation for the heating of hydrated copper sulfate?
CuSO₄.5H₂O ⇌ CuSO₄ + 5H₂O
Colour of anhydrous copper sulfate
White
How can the position of the following reaction be moved to the right?
Cu(H₂O)₆²⁺ + 4Cl⁻ ⇌ CuCl₄²⁻ + 6H₂O
Add conc HCl
What is the equation for the equilibrium constant Kc for the reaction: 2A + 3B ⇌ 2C + D?
[C]²[D] / [A]²[B]³
What are the units of Kc for the reaction: A + 3B ⇌ 2C + D
units for Kc: mol⁻¹dm³
What effect does an increase in temperature have on the Kc of an exothermic reaction?
Kc decreases
Equilibrium shifts in the endothermic direction (backwards) to oppose the change
How does increasing the concentration of iodine affect Kc and equilibrium position for the reaction:
I₂ + 2OH⁻ ⇌ I⁻ + IO⁻ + H₂O
No effect on Kc
Equilibrium shifts to the right
Equation for partial pressure
(mole fraction) x (total pressure of gas)
Equation for mole fraction
No. of moles of a gas / total moles of gas present
What is the equation for equilibrium constant Kp for the reaction: 2SO₂ + O₂ ⇌ 2SO₃?
p(SO₃)² / p(SO₂)² p(O₂)
What effect does an increase in pressure have on the value of Kp?
None
What change causes Kp of an endothermic reaction to decrease?
A decrease in temperature
System opposes change and moves in exothermic direction (to the left)
What is the only variable that has an effect on the value of Kp or Kc?
Temp
How are the values of Kp for the following two equations related?
1.2SO₂ + O₂ ⇌ 2SO₃ and 2. SO₂ + ¹/₂O₂ ⇌ SO₃
Kp(1) = (Kp(2) )²
What happens to the position of equilibrium of the following reaction when the temperature is increased? NH₃ + HCl ⇌ NH₄Cl
Shift to the left
System opposes change by moving in the endothermic direction (bonds are broken)
