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chem 123!! > intro to thermodynamics > Flashcards

intro to thermodynamics Flashcards

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1
Q

thermodynamics in general

A

study of bulk properties of matter - heat and conversion to/from mechanical and chemical energy

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2
Q

types of energy

A

potential, kinetic, chemical energy

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3
Q

system

A

specific part of universe we want to study

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4
Q

surroundings

A

everything in universe thats not the system

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5
Q

boundary

A

real or imagined separation between system and rest of universe

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6
Q

open system

A

can exchange energy AND matter w surroundings

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7
Q

closed system

A

can exchange energy but NOT matter w surroundings

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8
Q

isolated system

A

can exchange NEITHER energy nor matter w surroundings

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9
Q

state variables

A

describe conditions/state of the system DOES NOT MATTER how state was achieved

ex temperature, pressure, volume, density, mass, concentration

can be intensive or extensive

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10
Q

intensive state variables

A

independent of size of system

pressure, temperature, density, molar mass, concentration

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11
Q

extensive state variables

A

dependent on size of the system

volume, mass, number of moles, energy

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12
Q

state variables at equilibrium

A

properties of system are independent of time (they’re stable)

@ equilibrium variables are NOT independant of each other

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13
Q

Ideal Gas Law

A

mathematical relationship between thermodynamic state variables at equilibrium

PV = nRT

P(intensive)*V(extensive) = n(number of moles. extensive) R(gas constant intensive) * T(intensive)

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14
Q

ideal gas

A

gas phase non interacting particles, ceaseless random motion, perfect elastic collisions so no loss heat etc

works nicely for gases at high temperatures and low density/low pressure

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15
Q

non interacting

A

particles exert no force on each other except during collisitons

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16
Q

point particle

A

has no volume

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17
Q

ceaseless random motion

A

never at rest, no uniformity in direction or speed of motion

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18
Q

perfectly elastic collisions

A

translational kinetic energy is conserved during collisions (no friction)

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19
Q

perfectly elastic collisions

A

translational kinetic energy is conserved during collisions (no friction)

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20
Q

if closed system what is constant

A

volume and number of moles

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21
Q

closed system ideal gas at constant temperature, what happens to volume if double the pressure

A

decreased by half

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22
Q

closed system ideal gas constant pressure, what happens to temp if double volume?

A

doubled temp

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22
Q

closed system ideal gas constant pressure, what happens to temp if double volume?

A

doubled temp

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23
Q

internal energy state variable

A

all forms of chem energy in a system in joules

extensive state variable

kinetic and potential energy

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23
internal energy state variable
all forms of chem energy in a system in joules extensive state variable kinetic and potential energy
24
forms of internal energy
movement of molecules (translational/kinetic, rotational, potential) movement/energy within the molecule (vibrational, bonds) energy from interations between molecules (potential energy)
24
forms of internal energy
movement of molecules (translational/kinetic, rotational, potential) movement/energy within the molecule (vibrational, bonds) energy from interations between molecules (potential energy)
25
ideal gas, what is the energy in the form off
all kinetic energy
26
what forms can the movement of energy take?
heat (q) or work (w) - these are not state varibles, PATH variables
27
equation for work against a constant external pressure
w = -Pexternal*change in Volume
28
first law of thermodynamics
total energy of the universe is conserved change in E = q + w change in E = Efinal - Einitial
29
signs of q and w
heat q ABSORBED by system, q is positive for system heat taken from system, q negative for system work done ON system, w is positive for system system DOES work, w is negative for system
30
path/process variables
value depends on path taken to reach that value q and w are path variables, only exist during a change in the system. energy fluxes that cross the boundary during a process
31
internal energy of a system calculations (ideal gases)
all energy is kinetic, and proportional to temperature MONOATOMIC ideal gas: U = (3/2)nRT, where n is number of moles R is gas constant DIATOMIC ideal gas: U = (5/2)nRT
32
expansions with pistons
use PV = nRT, moles and pressure constant if heat is added, T increases as well as volume
33
piston undergoes rapid, non-isothermal compression what happens to temperature?
temp increases
34
piston undergoes rapid, non-isothermal expansion, what happens to temperature?
temp decreases
35
if a piston with ideal gas isothermal expansion T1 = T2, what is the change in energy?
0
35
if a piston with ideal gas isothermal expansion T1 = T2, what is the change in energy?
0
36
internal energy U of a ideal gas system based on temperature
increase in temp means increase in U decrease in temp, decrease in U constant temp, constant U
37
equation for work done by system at constant internal pressure
w = -Pext * [change in volume] for expansion, + change in volume therefore negative work for compression - change in volume therefore positive work
38
work for slow expansion equation
w = -nRTln(Vfinal/Vinitial)
39
reversible process
system can be restored to initial state without net effect on system or surroundings system is always in equilibrium
40
irreversible process
system cannot be restored to it's initial state without a net effect on system or surroundings
40
irreversible process
system cannot be restored to it's initial state without a net effect on system or surroundings
41
why are one step expansion irreversible?
the equation w = -P change in V is based on the pressure of the thing being worked against if for ex a rock is removed from the top of a piston, the pressure being worked against is small, but once the system has expanded its in a more ideal state therefore more work to get back to original
42
what is true about all paths connecting the same initial and final states?
the sum of q and w will be the same, based on change in U = q + w
43
for isothermal process what is true of q and w
q = -w, same magnitude opposite signs
44
change in E for an isolated system what does that imply for q and w?
0 if change in E = q + w, then if change in E is zero q and w must be equal in magnitude and opposite in sign
45
if given KE of 1 mol of an ideal gas, what happens to KE when double the number of moles
it doubles exactly
46
if given KE of 1 mol of an ideal gas, what happens to KE when double the number of moles
it doubles exactly
47
slide 13 3.1 post lecture slides
48
what happens if an isolated system is placed near heat etc
nothing, no energy can enter the system q w are both 0
49
increase in volume implies what w
negative, system has to do work against surroundings to expand
50
relationship between temperature and internal energy for ideal gas
directly proportional, so if internal energy decreases temp decreases as well
51
what do you use to calculate work for ideal gas at constant pressure
w = -pext * (change in V)
52
what is meant when given a reaction and calc work done by system when lsdkfjsldkfjs collected
work done by system in producing lskdfjlsfjd, if ideal gas you can use w = -Pext * (change in volume) change in volume would be the volume of the gas, which is V = nRT/P, the question should probably give you pressure
52
what is meant when given a reaction and calc work done by system when lsdkfjsldkfjs collected
work done by system in producing lskdfjlsfjd, if ideal gas you can use w = -Pext * (change in volume) change in volume would be the volume of the gas, which is V = nRT/P, the question should probably give you pressure
53
determining change in internal energy when given only volume and pressure ideal gas
we know for ideal gas temperature is directly proportionate to energy, so start by calculating change in temperature. you can use PV = nRT, isolating temperature and solve from there with change in T = Tf - Ti
53
determining change in internal energy when given only volume and pressure ideal gas
we know for ideal gas temperature is directly proportionate to energy, so start by calculating change in temperature. you can use PV = nRT, isolating temperature and solve from there with change in T = Tf - Ti
54
if change in T = 0 for ideal gas process, what is change in E and change in H?
all 0
55
main concepts to remember for thermodynamics
for ideal gas, energy is completely dependent on temperature so always start with that. change in T = 0, change in E and H = 0 PV = nRT, can be used to sub in pretty much any equation with ideal gasses for monoatomic ideal gas E = 3/2 nRT diatomic ideal gas E = 5/2 nRT

chem 123!! (4 decks)

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