There are several factors affect reaction rates ◦ Concentration ◦ Surface area (Particle size)...

There are several factors affect reaction rates◦ Concentration◦ Surface area (Particle size)◦ Temperature◦ Catalysts◦ Inhibitors

A catalyst is a substance that increases the rate of a chemical reaction without itself being used up in the reaction.

A catalysts provide an alternative energy pathway for the reaction.

The different pathway lowers the activation energy allowing more molecules to overcome the activation energy and produce products at a faster rate

H

A lower activation energy allows more molecules to overcome the activation energy, speeding up the reaction

An inhibitor is a substance that slows down, or inhibits reaction rates.

Uses◦ A preservative◦ A weed killer

When a reaction results in complete conversion of reactants to products chemists say it goes to completion

Not all reactions go to completion. They appear to stop because they are reversible

Reversible reactions can occur in both the forward and reverse directions

Forward N2 + 3H2 2NH3

◦ The reactants are N2 and H2

Reverse N2 + 3H2 2NH3

◦ The reactant is NH3

N2 + 3H2 ⇆ 2NH3

The forward and reverse reactions are happening at the same time.

Chemical equilibrium is a state in which the forward and reverse reactions balance each other because they take place at equal rates.

◦ Rateforward reaction = Ratereverse reaction

This does not mean the concentrations of the products and reactants are the same

Equilibrium is a state of action, not inaction. This process is dynamic; dynamic equilibrium.

http://www.youtube.com/watch?v=JsoawKguU6A

Law of chemical equilibrium states that at a

given temperature, a chemical system

may reach a state in which a particular ratio

of reactant and product concentrations has

a constant value known as Keq or

equilibrium constant.

Keq is the ratio of product concentrations to reactant concentrations.

A large Keq, Keq > 1 means the products are favored over the reactants

A small Keq, Keq < 1 means the reactants are favored over the products

Homogenous equilibrium means all reactants and products are in the same physical state

Ex: H2(g) + O2(g) H20(g)

Heterogeneous equilibrium is when the reactants and products are in more than one physical state.

Ex: H2O(g) + C(s) H2(g) + CO(g)

aA + bB cC +dD

products [C]c [D]d

reactants [A]a [B]b

= =Keq

**only use Keq for gases and aqueous compounds

1. Given N2(g) + 3H2(g) 2NH3(g) write the equilibrium constant expression for the reaction.

2. Given SO2(g) + O2(g) 2SO3(g) write the equilibrium constant expression for the reaction.

1. Given 2NaHCO3(s) Na2CO3(s) + CO2(g) +

3H2O(g) write the equilibrium constant expression for the reaction.

At equilibrium and 100°C a flask contains:[PCl5]=0.0325M[H2O]=0.025M

[HCl]=0.375M [POCl3]=0.250M

Calculate the Keq for the reaction PCl5(g) + H20(g) 2HCl(g) + POCl3(g)