chemical equilibria

Question 1

definition of reversible reaction

Answer 1

reversible reaction is one which can occur in both directions

Question 2

definition of dynamic equilibrium

Answer 2

a dynamic equilibrium refers to a reversible reaction in which the forward and reverse reactions are both taking place at the same rate, resulting in no overall changes in concentration.

Question 3

Kc equation

Answer 3

Kc = [product]^coeffecient / [reactants]^coeffecient

Question 4

Kp equation

Answer 4

Kp = partial pressure of product^coeffecient / partial pressure of reactants^coeffecient

gases only

Question 5

what does the magnitude of Kc or Kp mean?

Answer 5

small Kc / Kp (under 1) = position of equilibrium lies on the left. extent of conversion of reactants into products is small, so proportion of products to reactants is low.

large Kc / Kp = position of equilibrium lies on the right. extent of conversion of reactants into products is large, so the proportion of products to reactants is high.

Question 6

state the le chatelier’s principle

Answer 6

Le Chatelier’s principle states that if the conditions of a system at equilibrium are changed, the position of equilibrium shifts so as to reduce that change.

Question 7

effect of changes in concentration
draw graph

Answer 7

when concentration increases, by le chatelier’s principle, position of equilibrium shifts to right/left so as to decrease concentration of (stuff). backward/forward reaction is favoured

sharp increase when stuff is added, with a slow decrease of the stuff
decrease of the substance on the same side of the equation as stuff
increase of the other substances
decrease of stuff still ends up higher than before the addition of stuff

Question 8

effect of changes in total pressure
draw graph

Question 9

effect of changes in temperature

Question 10

effect of changes in catalyst

Question 11

does Kc change? (for concentration, pressure, temperature, catalyst)

Answer 11

Kc remains the same for concentration

Question 12

what does the relationship between Qc and Kc mean?

Answer 12

Qc < Kc: reaction will proceed in the forward direction to consume more reactants and form more products until Qc = Kc

Qc = Kc: system is at equilibrium

Qc > Kc: reaction will proceed in the backward direction to consume more products and form more reactants until Qc = Kc

Question 13

what does the sign for ΔG mean

Answer 13

ΔG < 0: forward reaction is spontaneous, there is a driving force in the forward direction, position of equilibrium lies to the right

ΔG > 0: backward reaction is spontaneous, there is a driving force in the backward direction, position of equilibrium lies to the left