Chapter 6 Flashcards
How is energy transferred?
What is it?
Through heat
The flow of energy caused by a temperature difference
What is chemical energy?
The energy associated with the relative positions of electrons and nuclei in atoms and molecules
Form of potential energy
What is the system in energy?
The system is the object with the energy initially
What is the surrounding in energy?
Are everything with which the system can exchange energy
What is the formula using mass velocity and kinetic energy?
KE= 1/2 mv^2
M in kg
V in m/s
KE in J
What are thermodynamics?
The general study of energy and its interconversions
What is the first law of thermodynamics?
The total energy of the universe is constant
The universes energy content does not change since energy cannot be created more destroyed
What is internal energy? Is it a state function?
E
The sum of the kinetic and potential energies of all of the particles that compose the system
Yes it is a state function since it depends only on the state of the system
What is the internal energy equation?
TriangleE= Efinal- Einitial
Or
Eproducts-EReactants
How does the internal energy of the surrounding compare to the energy of the system?
Is this the same for heat?
TriangleEsystem= -triangleESurroundings
Yes,
Qsystem=-Qsurroundings
When the system is positive where does energy flow?
Into the system from the surroundings
What is the equation of the internal energy involving work and heat transferred?
TriangleE=q+w
What is heat?
What’s temperature?
The exchange of thermal energy between a system and its surroundings caused by a temperature difference
Temperature is a measure of the thermal energy in a sample
Where does thermal energy always flow?
From matter at high temperatures to matter at lower temperatures
What is the formals using heat, heat capacity and change in temperature?
How about using specific heat capacity?
Q=C (TriangleT)
q= heat
C= heat capacity
Triangle T= change in temp
q=m x Cs x triangleT
What’s the difference between heat capacity, specific heat capacity, and molar heat capacity?
Heat- heat required to raise temp by 1 degree C
Specific Heat- heat required to raise 1 gram of substance by 1 degree C (J/g•C)
Molar heat- heat required to heat 1 mole of substance by 1 degree C (J/mol•C)
What is the equation for work, pressure and change in volume?
w=-PtriangleV
P= external pressure
V= litres
What is the heat at a constant volume equation?
🔺Erxn=qv+w
W=0 at co stang volume so
🔺Erxn=qv
What is the equation to find heat using a bomb calorimeter? What’s the equation if no heat escapes from the calorimeter?
qcal=Ccal • 🔺T
Ccal= heat capacity of entire calorimeter assembly
qcal=-qrxn
What is enthalpy?
What’s its formula?
The sum of a systems internal energy and the product of its pressure and volume
H= E + PV
🔺H=🔺E+P🔺V
🔺H=(Qp+w) + (-w)
🔺H=Qp (the heat at constant pressure)
What is an endothermic reaction compared to an exothermic one?
Endothermic- absorbs heat from its surroundings (🔺H is positive)
Exothermic- gives off heat to its surrounding (🔺H is negative)
What are the three rules with Hess’s law involving 🔺Hrxn?
- If the chemical equation is multiplied by some factor then 🔺Hrxn is also multiplied by the same factor
- If the equation is reversed then 🔺Hrxn changes sign
- If the equation can be expressed as a sum of steps then the 🔺Hrxn is the sum of the heats for those steps
What’s is the standard state for enthalpy?
For gas, liquids and solids, and substance in a solution
Gas- pure gas at pressure 1 atm
Liquid or solid- pure substance at 1 atm and at temp of interest (25C)
Substance in a solution- concentration of 1M
What is the standard enthalpy change ( 🔺Hdegree)
Change in enthalpy for a process when all reactants and products are in their standard states
Degree sign indicates standard states
What is the enthalpy of formation?
(🔺Hdegree f)
For a pure compound and a pure element in standard state
Pure compound- change in enthalpy when 1 mole of compound forms into constituent elements is standard state
Pure element in its standard state- 🔺Hdegree f= 0
What is the formula for calculating the standard enthalpy change for a reaction?
Reactants -> elements 🔺H1=-Ē🔺Hdegree f (reactants)
Elements -> products 🔺H2= +Ē🔺Hdegree f (products)
= reactants -> products 🔺Hrxn=🔺H1+🔺H2
