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CHM135 > thermochemistry > Flashcards

thermochemistry Flashcards

1
Q

theres two kinds of basic energy:

A

Potential (stored) and kinetic (motion)

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2
Q

Internal energy =

A

sum of all energy

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3
Q

On molecular scale, chemical bond energy =

A

potential energy stored in molecular clouds

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4
Q

energies of molecular moition =

A

Rotationa;, translational, vibrational

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5
Q

thermal energy

A

sometimes called energy of molecular motion

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5
Q

temperature is a common measure of

A

energy of molecular motion

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6
Q

ENERGY is the capacity to

A

do work or supply heat

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7
Q

1st law of thermodynamics

A

energy cannot be created or destroyed

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8
Q

All total energy of universe is ____

A

conserved

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9
Q

UNiverse equation

A

system + surroundings

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10
Q

If energy leaves the system, it must

A

enter the surroudings

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11
Q

energy change in energy system has to be accompanied by an _______ _______ change and the ____ must be ________

A

equal magnitude

signs

opposite

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12
Q

ΔE =

A

Eproducts - E reactants

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13
Q

state function

A

A function or property whose value depends only on the present state (condition) of the system (path doesn’t matter)

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14
Q

Example of state function

A

Arriving to Montreal with or with out layovers doesn’t matter. final position is the state function

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15
Q

Most changes to internal energy of system involve ______ of both _____ & ______

A

transfer

heat

work

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16
Q

ΔESYS =

A

work (w) - heat (q)

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17
Q

If w (work) = 0 then

A

it is example of energy transferred only as heat (q)

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18
Q

Heat or thermal energy will flow from _________ to _________ objects, eventually reaching _________ __________

A

higher-temp

lowe-temp

equal temp

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19
Q

When w = 0, ΔE < 0, q < 0 then

A

heat released to surrounding
(E initial > E final)

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20
Q

When w = 0, ΔE > 0, q > 0 then

A

heat absorbed to surrounding
(E intial < E final)

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21
Q

Mechanical work is the product of

A

w = force (F) x distance (d)

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22
Q

The larger the force or the longer the distance an object is moved, ….

A

the more work is done ON it

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23
Q

when is transfer of energy work only

A

when q = 0

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24
Q

When gas forming rxn in insulated container is attached to piston cylinder that pushes against it, the system

A

pushes the piston out, DOING WORK ON the surroundings

25
Q

Expansion work

A

The work done when the volume of a system changes in the presence of an external pressure

26
Q

Expansion work i also known as

A

Pressure volume work

27
Q

Expansion work at constant pressure (P = P surroundings) the formula is

A

w = -PΔV = -P(V final - Vinitial)

28
Q

More work is done when the volume change is

A

larger

29
Q

The sign of expansion work is negative because

A

The system is expanding and doing work. It LOSES internal energy by doing this work

30
Q

If the volume occupied by the reactants is larger than the volume occupied by the products,

A

Work is done on the system

31
Q

Enthalpy is a scale to keep track of the ______ of the _______________ transformation

A

energenetics

constant-pressure

32
Q

ENTHALPY (H) is defined as

A

H = E + PV

33
Q

Change in enthalpy (ΔH) formula

A

ΔH = ΔE +PΔV

34
Q

Change in enthalpy (ΔH) is equal to the amount of heat ________ or ______ in a ________ at CONSTANT PRESSURE

A

gained

loss

transformation

35
Q

if ΔH < 0 then

if ΔH > 0 then

A

exothermic (heat loss, is a product)

endothermic (heat gain, is a reactant)

36
Q

Multiplying a reaction increases ΔH by

reversing a reaction changes

A

by the same factor

the sign of ΔH

37
Q

heat capacity definition

A

amount of heat required to raise the temperature of an object or substance by 1C or K

38
Q

Heat capacity formula

A

q/ΔT

39
Q

Sand heats up really quick so it has _____ heat capacity

A

LOW

40
Q

Specific heat capacity definition and formula

A

Heat capacity per mass (1g)

c = q/(mass x ΔT)

41
Q

Molar heat capacity definition and formula

A

Heat capacity per mole

c = q/ (amount mole x ΔT)

42
Q

Energy is stored in different _______________

A

degrees of motion

43
Q

Higher heat capacity means _____ ________ given off

A

more heat

44
Q

Calorimetry

A

Science of measuring the heat exchanged in chemical reactions

45
Q

In calorimetry, the heat of reaction (qrxn) is measured __________ by means of a calorimeter. If rxn produces heat, the temperature of surroundings _________ and vice versa

A

indirectly

increases

46
Q

q rxn =

A
  • q calorimeter

= -(qvessel + qsolution +qother)

47
Q

example of constant pressure or coffee cup calorimetry

A

qsys (sample) = -q calorimeter (surrounding h20)

48
Q

HEAT CAPACITY of the calorimeter (often equal ot that of the surrounding water cuz heat absorption of vessel is minimal) provides the link between _____________ and _________ from which you can determine the _____ ______ of the system

A

ΔT

Heat gained/lost

enthalpy change

49
Q

Heat capacity (calorimeter) formula

A

q cal/ΔT cal

50
Q

Standard states of

pure substance

gas

substance in aquoeous solution

A

1atm

1 atm

1M concentration

51
Q

Standard enthalpy of a reactioon is indicated by symbol

A

ΔH° rxn

52
Q

what does ΔH° rxn indicate`

A

enthalpy change noted corresponds to all reactants and all products being present IN Standard state

53
Q

symbol for standard enthalpies of formation

also called

standard heat of formation

A

ΔH°f

54
Q

ΔH°f is enthalpy change for the formation of ________ of substance in its ________ from its ________ elements in their standard states

A

1 mole

standard state

constituent

55
Q

ΔH°f FORMULA

A

ΔH°f = ΔH°f (PRODUCTS) - ΔH°f (REACTANTS)

56
Q

ΔH°f CAN BE approximated by

A

accounting for bonds broken and formed using fomrula

ΔHrxn° ~~ BE (reactant bonds) - BE (product bonds)

57
Q

Hess law is

A

ΔH overall = ΔH1 + ΔH2 + ΔH3 …….

58
Q

what is texts notation for hess hlaw:

A

it uses ∑mΔH°f(products) - ∑nΔH°f(reactants)

59
Q

∑ is

m and n

A

sum of all

m and n is stoichiometric coefficients

60
Q

Explain work done ON vs work done BY

A

Work done on = something outside increases the energy inside the system

work done by = systems internal energy decreased when it did work. (DONE BY* SYSTEM DOES THE WORK)

CHM135 (8 decks)

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