Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

physical - yr2, s1 > 3d > Flashcards

3d Flashcards

1
Q

what conditions are needed the measure the temp dependence of U

A

we need V to be constant,, so W is 0,,

so dU = dQ

aka change in internal energy = change in heat exchange

bc U = q+w
and if w = 0 bc volume is constant,, (expansion = increase in volume) constant vol = no work bc no expansion so U = Q

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cv,m aka molar heat capacity at constant volume =

A

(dQ/dT)V

when N = 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

when we have state A and state B,, how can we find the heat difference between the 2.

A

we do Qb - Qa

where Qb is the heat of state b and Qa is the heat of state A.

=
Ub - Ua+ p(Vb - Va)

= (Ub+ pVb) - (Ua+ pVa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is enthalpy

A

H

sum of internal energy + pV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

equation for enthalpy // what it is // the equation for the definition

A

H = U + pV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

change in enthalpy in terms of q

A

Hb - Ha = qb - qa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

if we have 3 diff reaction that link,, how can we find delta H if we are given delta for all 3 reactions

A

delta H3 = delta H2 + delta H1

hess law
enthalpy is independent of route taken to get there,, there can be many different steps but they all end up giving the same total enthalpy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

temp standard state

A

298.15k

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

pressure standard state in bar and pa

A

1 bar
100,000 pa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

moles in standard state

A

1 mol kg-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

enthalpy of formation equation weird way

A

(- rea - rea ) + pro + pro

aka pro - reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Cpm equation involving enthalpy, temp and pressure

A

(dH/dT)p

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is enthalpy a function of. aka enthalpy is enthalpy bc of what (when t isnt standard value)

A

a function of temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

relation of H and T (when t isnt standard temp)

A

H(T P N) - H ( To P N)

u just put the values in for the diff compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what effects H and what is thr equation that links them all

A

H is affected by U and pV

so delta H = deltaU + delta(PV)in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

in an ideal gas,,, U and PV are function of what

A

temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

to make pressure a factor that effects a gas,, what must happen

A

there must be intermolecular forces of attraction,, these are not present in an ideal gas

so we think of van der waals interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

do solids and liquids have a large or small volume change

A

solids and liquids have a small volume change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

why do solids and liquids have a small volume chnage

A

bc they have a low compressability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

delta H for liquids and solids,, due to pressure being an effect bc they have van der waals and low compressability

A

delta H = V deltaP

not exactly tho. its an approx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

the progress of a reaction can be written as what

A

a single parameter:

E but curly ish

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

if we have A + B –> 2C ,, write how we find thr change in molar quantities of the reaction

A

we do

dNa/-1 = dNb/-1 = dNc/-2

which gives dE

aka the small change of extent of rea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

equation for reaction velocity

A

dE / dT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Nk =

A

NAo - E

aka the moles of smt = initial moles - extent of reaction.

makes sense tbhh,, u look at how many moles u had to begin with and then u take away the extent of the reaction to see how much u have currently.

25
Q

how do we find Na

A

NAo - E

26
Q

how do we find Nb

A

NB = NBo - E

27
Q

how do we find Nc. if c is the product and its stoich is 2

A

Nc = NCo + 2E

28
Q

extent of a reaction and finding number of moles: if its a reactant with a stoichiometry of 1,, whatdo we do to fing it

A

moles = initial moles - 1E

bc its got a stoich of 1 and as the reaction takes place,, reactants decrease.

so we subtract the extent of reaction

29
Q

finding extent of a reaction: how do we find current moles of a product with a stoichiometry of 3

A

current moles = initial moles + 3E

3 bc it has a stoichiometry of 3

and u add the extent of a reaction bc its a product,, and as the reaction occurs,, ur getting more product,, do u add extent of reaction!!!

30
Q

U in terms of everything that affects it including E

A

U = U ( T V E)

31
Q

if we have many diff chem reactions,, what else will we have many diff things of

A

we wll have many diff extents of reaction

one for each reaction im guessing

for us to add // subtract to the value of intiial moles to find the current moles

32
Q

what does (dU / dE) VT mean

A

its the amount of heat evolved per unit change in the extent of reaction.

aka how heat change chnages with a ddiff extent of reaction.

bc this is in the dQ reaction

33
Q

if dQ = …. (dU / dE) VT is negative,, what does this mean

A

it means that the reaction is exothermic

bc this is how the heat evolved changes as the ectent of reaction changes

so - heat = loss of heat = exothermic

and if its positive that means as the reaction goes on,, the heat evolved is positive so its endothermic as it would need to get heat from somewhere ,, aka the surroundings

34
Q

how do we express H in terms of extent of reaction

A

H = H ( T p E)

35
Q

heat of reaction per unit time change of E is the derivative of H wrt E =

A

H PT = (dH / dE ) pT

36
Q

2nd law of thermodynamics

A

entropy of an isolated system will always increase over time

37
Q

what is the change in internal energy if we return back to the original state,, and the system is closed

A

0 change in internal energy

there is no change

38
Q

what is the equation that represents that change in internal energy for a closed system when there is a cycle,, is 0

A

theta (long curvy line) dU = 0

39
Q

if we have a box type structure on a graph,, with p beig on the y axis and V being on the X axis,, and the corners being A B C and D going clockwise. A–> B will be the same,, but opposite to

A

C –> D

what is needed to get from A–> B is opposite of that needed to get from C–D bc its a carnot cycle.

40
Q

in the box example we’re taling about a carnot cycle, to get from A –> B it absorbs heat so to get from C –> D it must

A

return the heat // get rid of it

do the opposite of what it did.

41
Q

the work to get from AB issss=

A

Wab = N R theta1 ln ( Vb/Va)

theta 1 being the heat absorbed to get from A to B

42
Q

if A to B was isothermal ,, no change in temp,, Wab would beeee

A

Wab = Q ab

43
Q

Wcd would be

A
  • Qcd

bc ur removing heat bc ur going to the lhs of the x axis,, which is a lower volume.

44
Q

WBC is what compared to WDA

A

WBC = - WDA

45
Q

what the total work done by the carnot cycle calculated using

A

all the different work. work done by each edge of the box to get to the different edges.

46
Q

overall process eddiciency =

A

fancy n

47
Q

overall process efficiency equation =

A

W / Qab

48
Q

overall process efficience cannot exceed what

A

1

bc u cannot convert more than 100%

u do 1 - x to see how much was acc converted going between the diff states // corners

49
Q

overall process efficacy equation in terms of 1 and the route taken to get to the different corners

A

u have 1 - ( theta 2 / theta 1)

50
Q

efficacy of smt is dependent on what

A

theta 1 and theta 2

aka heat absorbed and returned in order to get to the diff states // corners of the box.

51
Q

(Q1/T1) < (Q2/T2) means its what

A

it means its an irreversible processss!!!

52
Q

what must occur for the process to be deemed as reversible

A

Q1/T1 = Q2 / T2

they must equal eachother to be reversible

53
Q

what changes in reversible reactions and by how much

A

temp, pressure, vol can change

by ‘d’ infinetesly small amounts

54
Q

irreversible reactions: t1 and q1 vs q2 and t2,, what is bigger than what

A

Q1/T1< Q2/T2

bc T1 is larger than T2.

the values arent equivalent meaning the values dont change by an infinitesily small amount like in a reversible reaction!!!!

so it must be an irreversible reaction.

55
Q

in a carnot cycle,, the reversible cycle (infinitesity small changes) issss

A

the outside of the 2 boxes stuck together by an edge!! aka lowkey the circumference of it

56
Q

in a carnot cycle,, when 2 cycles are combined,, where the 2 cucles combine,, what happens

A

these are the 2 adiabatic processes and they cancel out due to sign inversion

57
Q

how do we offset the isotherm process in carnot cycles

A

we combine two of them

this offsets the isotherm processes by a infinitesimal temperature amount.

so that heat absorbed from A to A’ at T1 is Q1

and heat absorbed a;onh A’ to B at T1 + deltaT is Q’1

58
Q

any process that has a closed path and chnages with infinitesimal small changes: we use the equation:

A

curly theta dQ/T = 0

which is the gibbs formula

bc DQ/T is a variable state

which gives us a measure of reversibility :

variable state = variables that describe the state of a dynamical system : yhh okay so shows reversibility bc we can see the state of the reaction!!

variable. smt that doesnt have a fixed pattern // changes.

physical - yr2, s1 (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions