Chem Chp 7 Flashcards
Thermodynamics
study of energy, work, and heat
3 Laws Thermodynamics
- Energy cannot be created or destroyed only converted from one form to another
- Universe spontaneously tends toward increasing disorder or randomness.
- Disorder of a pure perfect crystal at absolute zero is zero
molecules and atoms are in constant random motion and
frequently collide with each other
average kinetic energy of the atoms or molecules ____ with increasing temperature
increases
Collisions with sufficient enrgy will
break bonds in molecules
when reactant bonds are broken
new bonds may be formed and products result
We can only measure change in energy
TRUE
System
process under study
surroundings
encompasses the rest of the universe
Heat
transfer of thermal energy to the surroundings
exothermic reaction
releases energy to the surroundings
energy to break bonds is less than the energy given off when the bond forms
Energy is product
endothermic reaction
absorbs energy from the surroundings
energy to break bonds is greater than the energy realeased, the reaction needs more energy
Energy is reactant
Enthalpy
Heat
Change in enthalpy
energy released is represented with a negative sign (exothermic)
energy absorbed is shown with a positive sign (endothermic)
Most but not all exothermic reactions
are spontaneous
Most but not all endothermic reations
are NOT spontaneous
Entropy
Measure of the randomness of a chemical system- Represented S
Reactions that are exothermic and whose products are more disorder will
occur spontanously
Endothermic reactions producting products of low entropy ill
not be spontanous
Free Energy
Delta G represents the combined contribution of the enthalpy and entropy values
pg 224
Calorimetry
measurement of heat energy changes
Calorimeter
device used for these measurements
Specific Heat
The number of calories of heat needed to raise the temperature of 1 gram of the substance 1 degree celsious
Heat equation
Q= ms x delta T x SH
Fuel Value
Amount of energy per g of food
Nutritional Calorie
1 Kilo Calorie (1000 calories)
Chemical Kinetics
Study of the rate or speed of chemical reactions
Only effective collisions have
chemical reactions
Activation Energy
the minimum amount of energy required to initiate a chemical reaction
Activated Complex
the reaction proceeds from reactatnts to products through an extremely unstable state
Formation of the activate complex required
energy
Because this is an exothermic reaction
overall energy change must be a NET realsease of energy
Ions in a solution are
rapid
ractions invlolving covalents
generally slower
Large Molecules
proceed slowly
Effective Collisions
molecular collisions that have the correct collision oriltation to lead to product formation
Rate Increases as
Concesntration increases
Rate increases as temperature
increases
Ractions are the fastest in what states?
Liquid and Gas
Slowest when
Solid state
Catalyst
substance that increases reaction rate
Enzymes
biological catalyst in body
reaction order
represents the number of molecules that are involved in the formation of product
Complete Reaction
one in which all the reactants have been converted to products.
Equilibrium reactions
no further obvious change is taking place
Reversable reaction
shown by double arrow
Dynamic Equillibrium
a situation in which the rate of the forward process is a reversible reaction is exactly balanced by the rate of the reverse process.
Equillibrium constant
the relationship between the concentration of reactants and products in an equilibrium reaction
Le Chatelier’s principle
if stress is placed on a system at equilibrium the system will respond by altering the equilibrium composition in such a way as to minimize stress
Only gas equilibrium is affected by
pressure
Catalyst does NOT affect
equilibrium
