Chapter 7 - Equilibrium

Question 1

Closed System

Answer 1

A system that does not allow matter to transfer in or out, but allows for the transfer of energy to the surroundings. (e.g. a container with a lid).

Question 2

Open System

Answer 2

A system that allows matter to transfer in and out, such as an open beaker with gases inside.

Question 3

Equilibrium Constant (K)

Answer 3

The ratio of the concentration of products to the concentration of reactants in a system at equilibrium (note: units vary). Can only be changed by temperature.

Question 4

Equilibrium Yield

Answer 4

The percentage of product formed when a reaction reaches equilibrium.

Question 5

Extent of Reaction

Answer 5

The degree to which a reaction has proceeded in the forward direction (how many products have been made).

Question 6

Homogeneous System

Answer 6

A system where all reactants and products are in the same state (e.g. aqueous), as opposed to a heterogeneous system where there are different states.

Question 7

ICE Table

Answer 7

A table recording the initial number of moles, change in moles, and number of moles at equilibrium for a reaction. Used to calculate K.

Question 8

Reversible Reaction

Answer 8

A reaction which can proceed in both the forward and backward directions, represented by a harpoon ⇌.

Question 9

Le Chatelier’s Principle

Answer 9

“When a change is made to a system at equilibrium, the system will adjust to partially oppose the change.”

Question 10

Reaction Quotient (Q) / Concentration Fraction

Answer 10

The ratio of the concentration of products to the concentration of reactants in a system not at equilibrium (note: units vary).

Question 11

Irreversible Reaction

Answer 11

A reaction which can only proceed in the forward direction.

Question 12

Equilibrium

Answer 12

The point where the rate of the forward and backward reactions are equal, resulting in no observable change in macroscopic properties (colour, temperature, pH, pressure, concentration).

Question 13

Equilibrium Law

Answer 13

The value for K is constant for a system at equilibrium.

Question 14

Effect of Adding a Reactant at Equilibrium

Answer 14

• temporary increase in concentration of reactant
• system acts to oppose the change by decreasing concentration of reactant
• more products made
  Position of equilibrium moves to right (net forward reaction)

Question 15

Effect of Removing a Reactant at Equilibrium

Answer 15

• temporary decrease in concentration of reactant
• system acts to oppose the change by increasing concentration of reactant
• more reactants made
  Position of equilibrium moves to left (net backward reaction)

Question 16

Effect of Adding a Product at Equilibrium

Answer 16

• temporary increase in concentration of product
• system acts to oppose the change by decreasing concentration of product
• more reactants made
  Position of equilibrium moves to left (net backward reaction)

Question 17

Effect of Removing a Product at Equilibrium

Answer 17

• temporary decrease in concentration of product
• system acts to oppose the change by increasing concentration of product
• more products made
  Position of equilibrium moves to right (net forward reaction)

Question 18

Effect of Increasing Volume at Equilibrium

Answer 18

• concentration/pressure of all reactants/products temporarily decrease
• system acts to oppose the change by making concentration of particles increase
• position of equilibrium moves in direction which makes more particles

Question 19

Effect of Decreasing Volume at Equilibrium

Answer 19

• concentration/pressure of all reactants/products temporarily increase
• system acts to oppose the change by making concentration of particles decrease
• position of equilibrium moves in direction which makes less particles

Question 20

Effect of Increasing the Temperature of a Reaction at Equilibrium

Answer 20

• system acts to oppose the change by absorbing heat
• equilibrium moves in endothermic direction (left for exo, right for endo)
  Value of K changes.

Question 21

Effect of Decreasing the Temperature of a Reaction at Equilibrium

Answer 21

• system acts to oppose the change by removing heat
• equilibrium moves in exothermic direction (right for exo, left for endo)
  Value of K changes.

Question 22

Effect of a Catalyst on Equilibrium

Answer 22

• no change to position of equilibrium
  -allows equilibrium to be reached faster (increases rate of forward & backward reactions)

Question 23

Concentration-Time Graph

Answer 23

A graph with time on the x axis and concentration on the y axis, which visually represents how the concentration of the reactants/products change during a chemical reaction. Note: flat line = equilibrium. Changes in concentrations must be in mol ratio.