Equilibrium Flashcards
Describe the forward and backward reaction in a reversible reaction
-Forward reaction: initially reactants are used up quickly but then slow as their concentration drops
-Backward reaction: initially reactants are reformed slowly but then speed up as the concentration of products increases.
What is dynamic equilibrium?
point at which the rate of the forward reaction equals the rate of the backward reaction. The concentration of each substance remains constant. This only occurs in a closed system.
How can you calculate Kc?
the concentration of the products/ the concentration of the reactants
-the molar values in front of each species are the powers in the Kc expression
concentration units?
moldm-3
What is a homogeneous reaction?
all reactants and products are in the same state so all reactants and products are included in the final Kc expression.
What is a heterogenous reaction?
all reactants and products are in different states so we don’t include solids and pure liquids in the final Kc expression. This is due to their concentrations remaining constant.
What does the ICE acronym stand for?
Initial moles
Change in moles
Equilibrium moles
How do you use ICE? MUST PRACTICE
-calculate initial moles of reactant
-the initial moles of product is zero
-calculate equilibrium moles of product
-knowing the equilibrium moles of products, calculate the change in moles
-knowing the change in moles, calculate the equilibrium mole of the other compounds. (times the reactants by minus the change in moles of products)
-use equilibrium moles to calculate concentration
How do you use the value of Kc to find equilibrium concentrations? MUST PRACTICE
-substitute
-rearrange
-assume the different compounds hold the same concentration
What is total pressure?
sum of all the pressures of the individual gases (partial pressure)
How do you calculate total pressure? MUST PRACTICE
total pressure= pressure of reactants + pressure of products
-molar ratios can be used to calculate partial pressures but they must be on the same side of the reversible reaction
What is a mole fraction of a gas?
proportion of a. age in a gas mixture
How do you calculate the mole fraction of a gas?
number of moles of gas/ total number of moles of gas in the mixture
How do you calculate partial pressure?
mole fraction of gas (times) total pressure in mixture
what are the units for partial pressure?
kPa
Describe the Kp equilibria?
-only includes gases
partial pressures of products/ partial pressures of reactants
what is le chatelier’s principle?
if a reaction at equilibrium is subjected to a change in pressure, temperature or concentration, the position of equilibrium will move to counteract the change.
what is homogenous equilibria?
reactants and products are in the same state
Describe the effect of changing concentration on equilibria?
If we increase concentration of products/ reactants, equilibrium will shift to try to reduce concentration. The opposite will happen if concentration decreased. This only happens in homogenous equilibria.
Describe the effect of changing pressure on equilibria?
If we increase pressure, equilibrium will shift to the side with fewer number of gas particles which will reduce the pressure. The opposite will happen if pressure decreased. This only happens in homogenous equilibria.
Describe the effect of changing temperature on equilibria?
Increasing temperature will shift equilibrium in the endothermic direction which will reduce the temperature. The opposite will happen if temperature decreased. This only happens in homogenous equilibria.
what is the effect of catalysts on equilibria?
-no effects on the position of equilibria
-the rate of the forward and backward reaction will be increase equally
-will speed up the rate at which equilibrium is reached but have no effect on the yield
how does temperature affect Kp?
-if temperature change causes equilibrium to shift to the right, Kp will increase
-if temperature change causes equilibrium to shift to the left, Kp will decrease
how does changes in pressure and catalyst affect Kp and Kc?
Both have no effect on the value of Kp and Kc
how does temperature affect Kc?
-if temperature change causes equilibrium to shift to the right, Kc will increase
-if temperature change causes equilibrium to shift to the left, Kc will decrease
