Chapter 7 Flashcards
What two things play an important role in determining the extent and speed of a chemical reaction?
1) Thermodynamics, which deals with energy changes in chemical reactions
2) Kinetics, which describes the rate or speed of a chemical reaction
Thermodynamics
study of energy, work, and heat
3 Basic laws of thermodynamics?
1) energy cannot be created or destroyed, only converted from one form to another
2) the universe spontaneously tends toward increasing disorder or randomness
3) the disorder of a pure, perfect crystal at absolute zero is zero 0 (Kelvin)
Average kinetic energy of atoms or molecules does what with increasing temperature?
Increases
What happens when some collisions of molecules occur with sufficient energy?
can break bonds in molecules
What can happen when a reactant bond is broken?
new bonds may be formed and products result
System?
contains the process under study
Surroundings?
encompass the rest of the universe (system)
Heat
transfer of thermal energy to the surroundings; sometimes consider heat flow
Calorimetry
Experimental strategies for measuring temperature change and calculating heats of reactions
Exothermic reaction
Releases energy to the surroundings (surroundings become warmer)
representative with a negative sign
Endothermic reaction
absorbs energy from the surrounds (surrounding become colder)
representative with a positive sign
Enthalpy
term used to represent heat and is symbolized as H
If H reactants > H products, what is H?
H must be negative and the reaction is exothermic
If H reactants < H products, what is H?
H must be positive and the reaction is endothermic
Entropy
A measure of the randomness of a chemical system.
Symbol for entropy?
symbol S
Free Energy
symbol G, represents the combined contribution of the enthalpy and entropy values for a chemical reaction
4 situations of G
- H (neg) & S (pos), G is always pos, regardless of temp
- H (pos) & S (neg), G is always neg, regardless of temp
- H (pos) & S (neg), G depends on temp
- H (neg) & S (neg), G depends on temp
specific heat
number of calories (cal) of heat needed to raise the temperature of 1 gram (g) of the substance 1 degree Celsius (c).