Thermochemistry and Rates of Reactions Concept Map

the change in enthalpy of the targeted reaction

the sum of the change of enthalpy for each separate step to get to the targeted reaction

Calculate state functions

Change in Enthalpy

ΔHtarget = ΣΔHknown

Reverse sign of ΔH

Chemical equations is reversed

Alter ΔH in the same way

the coefficients of a chemical equation is altered

multiplying or dividing by a constant factor

change in Gibb's energy

Change in Entropy

Germain Hess, a Swiss Chemist

Law of additivity of reaction enthalpies

Car companies when building an engine

how much energy the car engine uses or produces when it burns fuel

determine efficiency of an engine

Human body when we exercise and burn calories

the amount of calories burned during a workout

track individual progress and meet their optimal shape

the study of ways to make chemical reactions go slower or faster

rate of reaction

the rate at which the product is formed

the rate at which the reactant is consume over a time interval

Change in concentration per unit time

r = Δc/Δt

mol L-1 s-1

average rate of reaction

the speed of the reaction over a period of time

instaneous rate of reaction

the speed of the reaction at a particular point in time

Chemical nature of reactants

similar elements (in the same group) react similar

gold and silver

react slow in air

Concentration of reactants

initial concentration is increase

reaction rate increases

initial concentration is decrease

reaction rate decreases

Surface area

surface area of reactant in a hetrogeneous system is increased

reaction rate increases

temperature

temperature increase

reaction rate increases

temperature decrease

reaction rate decreases

catalyst

a substance that is mostly used to speed up rate of reaction

being consumed itself

Disappearence of reactant

Appearance of products

Collison Theory

Particles are in constant random motion at various speeds in a chemical reaction

kinetic energy of particles

the temperature of the sample

higher the temperature, the more particles with higher kinetic energy

lower the temperature, the less particles with higher kinetic energy

particles must collide

each other or the walls of the container

Effective Collisions

colliding particles has sufficient energy and collide in correct orientation

break bonds and form new bonds

transition state or activated complex

ineffective Collisions

colliding particles rebound

unchanged in nature

frequency of collisions and the fraction of those collision

rate = frequency of collision x fraction of collisions that are effective

Collision Frequency

surface area

concentration

temperature

Fraction effective

temperature

nature of reactant

catalyst

Homogenous

Reactants and Catalysts are in the same state

Heterogenous

Reactants and Catalysts in different physical states

reaction mechanism

the sequence of two or more simple reactions that continue to form the overall reaction

activation energy

the difference in energy between the reactant and the transition state

minimum energy required for particles to collide and rearrange in structure

fewer particles with sufficient energy required to reach the transition state

more particles with sufficient energy required to reach the transition state

rate-determining step

slowest step in reaction mechanism

having the highest activation energy

reaction intermediate

a substance that is formed during reaction and consumed when the reaction is complete

elementary steps

steps in a reaction mechanism that only involves 1, 2, or 3 particles collisions

Help determine reaction rates

Theoretical effects

Chemical nature of reactant

threshold energy

the minimum kinetic energy required to convert kinetic energy to activation energy

formation of the activated complex

Energy of collisions

More frequent and effective collisions

distribution of speeds among particles at a given temperature

Number of molecules with
certain kinetic energy

Represents different energies

Affects on collision theory

Nature of chemical substances reacting

Bonds to be broken

effective collisions

Increase in concentration

Increases rate of reaction

Higher concentration = more particles in volume
which increases the likelyhood of effective collisions

Increase in surface area

Gives more room for volume

Effective collisions

Rise in temperature

Causes particles to move and react faster
according to particle theory

Chances of collisions increases

Presence of catalyst

Provides alternate pathway

Larger fractions of collisions are effective

enhances our knowledge on the systems around us and improve quality of life

Usage in everyday life

Cleaning Items

How different products have their own effect

Different products react on different surfaces and clean specific things

Unique to their own property

Counter cleaners, toilet cleaners etc.

React differently to get rid of unwanted substances as fast as possible

Cooking

baking cookies

Cookies bake faster at higher temperature

Faster rate of chemical reaction

the affect of medications on different people's bodies

the best drug for different diseases

the concentration over time

Some medications work close to instantaneously

Tylenol

Advil

used to predict dosage use

Kids would take a low dose due to
undeveloped systems --> rate of reaction
occurs fast with low dose

Higher dose would work faster
(greater concentration)

Adults due to developed
body types

Some take a lot longer to reach equilibrium

how serious the condition is

reaction takes longer to fight off pathogens