Chapter 7 Flashcards
What is a system?
part of the universe where the study is focused
What is the immediate surrounding?
the surroundings that the system affects
What is energy?
capacity to do work or produce heat
What is the law of conservation of energy aka 1st law of thermodynamics?
states that energy can be converted from one form to another but never created nor destroyed
What are exothermic reactions?
system release energy
What are endothermic reactions?
system absorbs energy
What will the energy number be if the reaction is endothermic?
positive
What will the energy number be if the reaction is exothermic?
negative
What is enthalpy?
change in enthalpy (Delta H) of a system equals the flow of heat into or out of a system
What is the equation for change in enthalpy of a system?
delta H Reaction = delta HProducts –delta HReactants
What is a state function?
variable that only depends on the state
that the system is in, value does not depend on the path taken to reach that specific value.
How is enthalpy like a state function?
there will be 0 change in total heat going from reactant to product since the internal heat within a pathway can’t change (no matter how many paths you
What is the equation for the enthalpy of a system?
H = internal energy of a system + pressurexvolume
What does delta H also equal when PRESSURE IS CONSTANT?
delta H = q
What is calorimetry?
science of measuring heat
What is heat capacity?
amount of heat needed to raise the temperature of a substance by 1 degree NOT INCLUDING MASS
What is specific heat capacity?
is the amount of energy required to
raise the temperature of 1 gram of substance by 1 ºC
What are the units of specific heat capacity?
Units of J/ºC•gor J/K•g
What is molar heat capacity?
The amount of energy required to raise
the temperature of 1 mol of substance by 1 ºC
What are the units of the molar heat capacity?
Units of J/ºC•mol or J/K•mol
What is the equation for heat transfer?
q = smΔT
What is Hess’s law?
If a process can be written as the sum of several processes, the change in enthalpy (DH) of the process equals the sum of the enthalpy changes of the individual steps
In Hess’s law, what happens to the sign of the enthalpy when you switch products and reactants?
you switch the signs
The magnitude of ΔH is directly proportional to…
the amount of reactant and products in a reaction
What is the standard enthalpy of formation?
the change in enthalpy that accompanies the formation of 1 mole of a compound from its elements
What is the standard enthalpy of formation symbol?
ΔHfº
What is the equation for the standard of enthalpy?
(all products) - (all reactants)
In the standard of enthalpy of formation equations, what is the number of lone elements?
0
`What is bond strength?
defined as the energy required to break the bond
What influences the bond values for bond energies?
chemical “environments”
What is the equation for the energy of reaction?
sum of bonds broken minus the sum of bonds formed
What are examples of state functions?
potential energy, temperature, enthalpy
q system = - q surroundings means what?
heat of system will be = to opposite signs of heat of its surroundings
q metal = -qwater means what?
heat of metal will be equal to opposite signs of heat of water
