Chapter 7 - Equilibrium

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).

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

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.

The percentage of product formed when a reaction reaches equilibrium.

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

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.

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

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

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

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

A reaction which can only proceed in the forward direction.

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).

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

• 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)

• 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)

• 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)

• 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)

• 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

• 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

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

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

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

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.