Thermochemistry Flashcards
What are isolated, closed, and open systems?
isolated: cannot exchange energy or matter with surrounding closed: can exchange energy but not matter with surroundings open: can exchange energy and matter with surroundings
What is the area under a pressure-volume graph equal to?
work
What does 1st law of thermodynamics become for an isothermal process?
W=Q since when change in T = 0, change in U = 0
what does 1st law of thermodynamics become for an adiabatic process?
change in U = -W since when no heat exchange between system and environment, Q = 0 in other words, change in U equals work done “ON” the system (the negative of the work done “BY” the system)
What does the curve of an isothermal process look like on a pressure-volume graph?
hyperbolic curve
What does an isobaric process appear as on a pressure-volume graph?
a flat line pressure is constant
What does the 1st law of thermodynamics become for an isochoric/isovolumetric process?
change in U = Q since when no change in volume, no work is done by the system
what does an isochoric/isovolumetric process look like on a pressure-volume graph?
a vertical line volume is constant
What are standard conditions, and what problems are they used for?
25 degrees Celsius, 1 atm, 1 M kinetics, equilibrium, thermodynamics
what are standard temperature and pressure, and what problems are they used for?
0 degrees Celsius, 1 atm ideal gas calculations
what is the definition of boiling point?
the temperature at which the vapor pressure equals the ambient pressure
what is the critical point on a phase diagram?
the point at which there is no distinction between liquid and gas phases
How does sweat help prevent overheating?
evaporation is an endothermic process, so heat energy is absorbed from the body by the sweat so that sweat particles gain enough kinetic energy to evaporate
What is heat (Q)?
the transfer of energy from one substance to another due to their difference in temperature
Under what condition is enthalpy equivalent to heat?
constant pressure
what is calorimetry?
the way of measuring the transfer of heat
what is the definition of specific heat?
the amount of energy required to raise the temperature of 1g of a substance by 1 degree
what is heat capacity?
mass times specific heat
what is the process to solve heat transfer problems? ex. mix two substances with different temperatures and determine equilibrium temperature
- qcold = -qhot
- mcAT = mc(-AT)
- ATcold = Tf - initial T
AThot = initial T - Tf
what type of calorimeter is used to determine heat of combustion?
bomb calorimeter or decomposition vessel
constant volume calorimetry –> work is zero
what is the heat of fusion?
the enthalpy change to melt a mole of a solid
what is heat of vaporization?
the enthalpy change to turn a mole of liquid to gas
what is standard heat of formation?
enthalpy required to form one mole of compound from its constituent elements in their standard states
what is standard heat of reaction?
enthalpy change that occurs when reaction is carried out under standard conditions
what is bond dissociation energy or bond enthalpy?
average energy required to break a particular bond between atoms in the gas phase (endothermic)
what is standard heat of combustion?
enthalpy change that occurs for the combustion of one mol of a fuel
what is the second law of thermodynamics? what is entropy?
energy spontaneously disperses from being localized to being spread out if it is not hindered from doing so. In other words, entropy of universe is increasing.
entropy is the measure of this dispersal at a specific temperature
