Chemical Equilibrium When forward and reverse reactions are occurring under the same conditions and at the same rate Static At rest; not changing.

Chemical Equilibrium• When forward and reverse reactions are

occurring under the same conditions and at the same rate

Static• At rest; not changing

Steady State• Constant change but unlike equilibrium

there is no reverse reaction

An open pan of water is boiling on a stove. The temperature of the water is constant.• Steady state

A balloon contains air and a few drops of water. The pressure in the balloon in constant.• Equilibrium

A colony of ants are going about their daily routine in an anthill. The population of the anthill is constant.• Equilibrium

A Bunsen burner burns in the lab to give a well-defined flame. Supplies of gas and air are constant.• Steady state

A line of Chi-Hi students at the pop machine. Every time money goes into the machine, a can of pop comes out.• Steady state

A measure of how fast the reaction proceeds

If the rate is fast, a large amount of reactants are being converted to products.

If the rate is slow, a small amount of reactants are being converted to products.

Reaction rates can be controlled if we understand the factors that influence them.

Chemical reactions occur through collisions between molecules or atoms

High energy collisions lead to products and low energy collisions do not.• This is because of the activation energy

Activation energy – the energy required to begin to break these bonds

The rate of a chemical reaction generally increases with increasing concentration of the reactants.

As the reaction proceeds, there are fewer reactant molecules (because they have turned into products) and the reaction slows down.

The rate of a chemical reaction generally increases with increasing temperature of the reaction mixture.

Raising the temperature makes the molecules move faster therefore they experience more collisions pre unit time, resulting in faster reaction rates.

Reversible reaction – a reaction where the products can reform reactants • i.e. ice• A reaction that can proceed in the forward and

reverse direction

Irreversible reaction – one-way reactions• Burning paper

Dynamic Equilibrium – the condition in which the rate of the forward reaction equals the rate of the reverse reaction

At dynamic equilibrium the rates of the forward (left to right) reaction and the reverse reactions are equal

• The forward and reverse reactions do not stop; they are in a dynamic system

• Proof: A broken crystal in a saturated solution will repair as the crystal is dissolving and forming a precipitate at the same time

No change in observable properties

Changes take place at the molecular level

Rates of forward and reverse reactions are equal

Equilibrium conditions can change (but the system will adjust to again be at equilibrium)

At dynamic equilibrium the forward and reverse reaction rates are the

same. Since the rates are the same, the concentrations are no longer

changing. However, just because the concentrations of the reactants and

products no longer change at equilibrium, does not imply that the

concentrations of reactants and products are equal to one another at

equilibrium.