Enthalpy and Entropy Study Guide

Catalysts

increase the rate of chemical reactions without being consumed

Enzymes

naturally occurring catalyst in living things

Substrate

what enzyme works on

Reaction rate

expressed as change in reactant concentration over time

Kinetics

study of reaction rates

Solvent effects

solvent may form hydrogen bonds with reactant -slows reaction

Equilibrium

when reaction rates of forward and reverse reactions become the same

Le Chatelier’s principle

if stress is applied to system at equilibrium, the composition of system will change to relieve stress

Gibbs free energy

brings together the ideas of how heat, temperature, and Entropy affect a reaction

Entropy

degree of disorder

Enthalpy

heat energy in a substance that depends on mass of substance

Absolute temperature

kelvin scale. Absolute zero = zero kelvin

Specific heat capacity

amount of heat energy needed to raise the temperature of 1g by 1*C

H comb

heat of combustion

H fus

heat of melting

H vap

heat of vaporization

H soln

heat of solution

H f

heat of formation

Endothermic

reaction takes in heat from surroundings

Exothermic

reaction gives off heat to its surroundings

System

the reaction

Surroundings

the rest of the universe

Calorimetry

study of heat flow and heat exchange

Rate limiting step

step in chemical reaction that determines the rate. The slowest step

6 ways to increase reaction rate

increase temperature, increase surface area, reduce solvent effects, catalysts, concentration of reactants, and phase

Why do we use Kelvin scale?

Zero Kelvin=zero heat

1st of law of thermodynamics

energy in the universe is conserved

2nd law of thermodynamics

Entropy in universe is constant in a reversible process

3rd law of thermodynamics

perfectly ordered system, with only 1 possibly means entropy will equal zero

Will an exothermic reaction always be spontaneous?

No, entropy is an important consideration.

Specific heat capacity of water

4.184 J/g*C

Collision theory

Reactants must collide/touch in order to react and they must be in the correct orientation and have enough energy