Entropy

List in order of increasing entropy:

Solid, gas, liquid

One major driving force in reactions is to increase the state of disorder (entropy) or randomness of particles.

(solid, liquid, gas)

nature of reactants

surface area exposed

concentrations

temperature

presence of catalyst

1. State the collision theory of reaction rates

2. How is the reaction rate related to concentration

1. There must be collisions between reactants. Reaction rate depends on number of collisions per unit time and the percent which are successful. (Have sufficient energy)

2. Reaction rate is directly proportional to the concentrations of reactants 

1. Activation Energy

2. Catalyst

1. The energy necessary for a reaction to begin. Obtained from the kinetic energy released during collision

2. A catalyst is introduced into a reaction to speed it up or slow it down. It is not consumed. An increase or decrease of activation energy results from an alternate reaction path.

1. Law of Mass Action

2. Specific rate constant

1. The rate of a chemical reaction is proportional to the product of the concentrations of the reactants, each raised to the appropriate power

2. Symbol is "k" in a rate equation. A constant specific to temperature and reaction which is part of every rate equation

How is the order of a reaction calculated?

What is the order of

H₂ + I₂ ↔ 2HI?

By adding the exponents in the reaction rate equation

Rate = k[H₂][I₂]

1 + 1 = 2 Reaction is second order

(note: the exponents of the concentrations of H₂ and I₂ are obtained experimentally not form their coefficients in a balanced chemical reaction.)