Chem 2 test 3

Adding a catalyst

- Does not change K - Does not shift the position of an equilibrium system - System will reach equilibrium sooner

Chemical equilibrium is achieved when:

- The rates of the forward and reverse reactions are equal. -The concentrations of the reactants and products remain constant.

A reaction with an equilibrium constant Kc= 1.5 x 10-25 would consist of which of following at equilibrium?

All the reactants

Le Chatelier's Principle

Applied to changes in concentration or pressure can be understood by having K have a constant value. The effect of temperature on equilibrium. Involves a change in the equilibrium constant.

Catalysts

Are substances that affect the speed of a reaction without being consumed.

Reaction rate changes:

As time goes on, the rate of a reaction generally slow down... because the concentration of the reactants decrease.

The presence of a catalyst in a chemical reaction will increase the reaction rate by:

Decreasing the activation energy.

Catalyst lower

Ea for both forward and reverse reactions.

The rate law

Expresses the relationship of the rate of a reaction to the rate constant and the concentrations of the reactants raised to some powers.

An increase in temperature will increase the rate of a chemical reaction because...

Increased temperature increases the number of effective collisions.

Which one of the following changes would alter the rate constant (k) for the reaction 2A+B products?

Increasing the temperature.

Equilibrium

Is a state in which there are no observable changes as time goes by

Reaction quotient(Qc)

Is calculated by substituting the initial concentration of the reactants and products into the equilibrium constant (Kc) expression.

Reaction rate

Is the change in the concentration of a reactant or a product with time (M/s).

Activation energy

Is the minimum amount of energy required to initiate a chemical reaction.

Half-life

Is the time required for the concentration of a reactant to decrease to half of its initial concentration.

When the volume of the container is increased the equilibrium will shift:

Right

gases

Tend to react faster than liquid, which react faster than solids

Qc = Kc

The system is at equilibrium.

Qc < Kc

The system proceeds from left to right (products) to reach Equilibrium.

Qc > Kc

The system proceeds from right to left (reactants) to reach equilibrium.

Small molecules

tend to react faster than larger molecules