Brookes (L1-L9) Flashcards
What are the 3 types of chemical system?
Isolated: no exchange of energy or mass (material)
Open: exchange of energy (heat, work) and material
Closed: exchange of energy only not material
What is the difference between thermodynamics and kinetics and is represented by what part on an energy diagram
Thermodynamics: energy exchanges involved between different systems, relates to the enthalpy change between reactants and products
Kinetics: how quickly a reaction occurs, related to the activation energy in a reaction profile
What are the 4 types of closed systems?
Isobaric: constant pressure
Isothermal: constant temperature
Isochoric: constant volume
Adiabatic: no heat flow between system and surroundings (but can still have work done to)
What are the equations and definitions of internal energy?
Total energy of a system
Change in U = Ufinal - Uinitial
Change in U = q + w
What are the 3 assumptions of kinetic theory of gases?
- A gas consists of molecules of mass m and diameter d which are in constant random motion
- Size of molecules is negligible compared to the distances they travel
- No interactions between molecules except for perfectly elastic collisions (no energy loss)
Define temperature and heat
temperature: the average kinetic energy of particles/molecules in a material
heat: the flow of energy between objects of different average kinetic energy (temperature)
define work and its equation
A force in a particular direction
w = f x d
w = - P x change in V
What is a reversible process?
Direction of a reversible process can change by making an infinitesimal change to a variable/conditions (small differences)
What is the difference between a state function and path function? + examples
State function: only depends on a systems energetic state, what a system has (eg. U, temp, pressure)
Path function: amount of energy intrinsically associated with a process, what a system can do (eg. work, heat)
What is enthalpy change + its equation?
A measurement of heat changes to the system (can result in temperature change)
H = U + PV
(Or the energy within a system + the energy needed to create space for the system to exist)
what is PV in the enthalpy (H) equation?
The amount of work done to create space for the system to exist within the atmosphere (pressure x volume)
What are the standard state conditions of a material?
25 degrees (298.15K), 1 bar/ 1 atm / 1 x 10^5 Pa
What is the standard state?
The stable form of a substance under standard conditions
What is the definition of heat capacity and what is the equation for it?
Relating the temperature change of the whole system when a certain amount of heat is delivered to it (can be constant pressure or volume)
Units: J K^-1
C = change in heat / change in temperature
Define specific heat capacity and units
The amount of energy needed to raise 1kg of a material by 1 K
J kg^-1 K ^-1
Define molar heat capacity and units and equation
Heat energy to raise 1 mole of a substance by 1K
Units: J mol^-1 K^-1
total heat capacity = no. of moles x molar heat capacity
What are the symbols for heat capacity, specific heat capacity and molar heat capacity?
Heat captivity: capital C
Specific heat capacity: Lower case c
Molar heat capacity: capcital C with m
How do you combine heat capacities?
C = moles or mass of A x heat capacity of A + moles or mass of B x heat capacity of B ….
Enthalpy of formation for enthalpy equation
H = products - reactants
Enthalpy of combustion equation for enthalpy change
H = reactants - products
What is included within internal energy?
Intermolecular interactions and intramolecular interactions (chemical bonding)
ion ion interaction equation
u (r) = (coulomb constant x charge 1 x charge 2) / distance between them (r)
where constant = 8.99 x 10^9 Nm2c-2
what is the significance of positive and negative energy valuesin terms of bonding
positive: repulsive energy (not energetically favoured)
negative: attractive energy (energetically favoured)
what is the dipole equation
dipole moment = charge (equal magnitude but opposite sign) x distance between charges