Thermochem

Question 1

kinetic energy associated with

random motion of particles

Answer 1

thermal energy

Question 2

potential energy related to the

arrangement of particles

Answer 2

chemical energy

Question 3

an object, or collection of objects, being studied

Answer 3

system

Question 4

everything outside the system that can exchange

energy and/or matter with the system

Answer 4

surrounding

Question 5

heat is * and * property

Answer 5

energy transferred due to temperature difference

extensive property

Question 6

temperature is * and * property

Answer 6

measure of average ke or intensity of heat?

intensive property

Question 7

exothermic
endothermic
qsystem:

Answer 7

exo: q sys < 0
endo: q sys > 0

Question 8

energy transferred as heat that is required to raise

the temperature of 1 g of a substance by 1 K

Answer 8

specific heat capacity

J/g-K

Question 9

energy transferred as heat that is required to raise

the temperature of 1 mole of a substance by 1 K

Answer 9

molar heat capacity

J/mol-K

Question 10

if two objects have the same mass, the object having the larger specific heat capacity will undergo the * temperature change for a given amount of energy transferred

if two objects have different masses, but the same specific heat capacity, the * object will undergo a smaller temperature change for a given amount of energy transferred

if two objects have different masses and different specific heat capacities, the temperature change must be calculated from the *

Answer 10

smaller

larger

conservation of energy

Question 11

larger specific heat capacity = * temperature change

Answer 11

smaller

Question 12

q = mc(delta T)

if heat of vap, sub or fus; q = ?

Answer 12

q = heat of (v,f,s) * mass

Question 13

work associated with a change in volume (ΔV)
that occurs against a resisting external pressure (P)
formula and unit

Answer 13

pressure-volume work
P - m^3
(1 Pa = 1 kg/m-s^2) 
delta V = m^3
J = kg-m^2/s^2

Question 14

If work was done by
the system:
If work was done on
the system:

Answer 14

If work was done by
the system: w < 0 (expansion)
If work was done on
the system: w > 0 (compression)

Question 15

First law of thermodynamics:
Energy can neither be created nor destroyed.
It can only be transformed into another form of
energy through the interaction of *

Answer 15

heat (q),

work (w), and internal energy (U).

Question 16

First law of thermodynamics:
the energy change for a system (ΔU) is
the sum of the energy transferred as * and the energy transferred as * between the system and its surroundings

Answer 16

heat (q), work (w)

ΔU = q + w

Question 17

The * in a chemical system is the sum
of the potential and kinetic energies inside the system,
that is, the energies of the atoms, molecules, or ions in
the system.

Answer 17

internal energy (U)

Question 18

q>0 (+)
q<0 (-)
w>0 (+)
w<0 (-)

Answer 18

endothermic, U increases
exothermic, U decreases
work done on the system, U increases
work done by the system, U decreases

Question 19

The total energy of the universe is *

formula

Answer 19

constant
ΔUuniverse = 0
ΔUuniverse = ΔUsystem + ΔUsurroundings
ΔUsystem = - ΔUsurroundings

Question 20

thermodynamic property wherein changes in these
quantities depend only on the initial and final states
examples:

Answer 20

STATE FUNCTIONS

ΔT, ΔU, ΔV, ΔH, ΔP

Question 21

quantities that depend on the pathway taken to
get from the initial condition to the final condition
examples:

Answer 21

PATH FUNCTIONS

q, w

Question 22

measure of energy transferred as heat in constant pressure

formula:

Answer 22

enthalpy

ΔH = qp= ΔU + PΔV

Question 23

SIGN CONVENTIONS
- ΔH =
+ΔH =

Answer 23

• ΔH = exothermic process

+ΔH = endothermic process

Question 24

If a system is at constant volume:

ΔUsystem =

Answer 24

ΔUsystem = q(system) + w(system) = qv

Question 25

If the system is NOT at constant volume:

ΔUsystem =

Answer 25

ΔUsystem = qp + w(system)

Question 26

qv = qp + w
Since w = -PΔV and qv = ΔU, then
ΔU = qp – PΔV
qp = ?
ΔH = ?

Answer 26

qp = ΔU + PΔV
ΔH = ΔU + PΔV

Question 27

ØAt constant volume:
qv = ?
ØAt constant pressure:
qp = ?

Answer 27

ØAt constant volume:
qv = ΔU
ØAt constant pressure:
qp = ΔH

Question 28

ΔH = qp= ΔU + PΔV
sign conventions
*ΔH = exothermic process
*ΔH = endothermic process

Answer 28

negative ΔH = exothermic process

positive ΔH = endothermic process

Question 29

pure, unmixed reactants in their standard states* have
formed pure, unmixed products in their standard states
unit:

Answer 29

STANDARD REACTION ENTHALPY, ΔrH°

units: kJ/mol (or kJ/mol-rxn)

Question 30

the most stable form of the substance in the
physical state that exists at a pressure of 1 bar
and at a specified temperature (usually 25 °C)

Answer 30

STANDARD STATE

Question 31

enthalpy changes are * to each reaction
§ * equation + states are important!!
§ enthalpy change depends on the number of *
of reaction (number of times it is carried out)
§ for chemical reactions that are the reverse
of each other, ΔrH° values are numerically
the *, but *in sign

Answer 31

specific
balanced
moles
same, opposite

Question 32

heat is shown as * of the chemical reaction

heat transferred is an * property

Answer 32

part

extensive

Question 33

measurement of energy evolved or absorbed
as heat in a chemical or physical process
apparatus: *
à types of calorimetry:
§ constant pressure:
§ constant volume:

Answer 33

calorimetry
calorimeter

§ constant pressure
coffee cup calorimeter
§ constant volume
bomb calorimeter

Question 34

measure the amount of energy transferred as heat under constant-pressure conditions
= enthalpy change, ΔH
formula

Answer 34

àcoffee cup calorimeter

qrxn + qsoln = 0

Question 35

evaluate the energy released by the combustion
of fuels and the caloric value of food

constant volume = no P-V work done on/by the system
= energy is transferred as heat only = internal energy, ΔU

formula

Answer 35

bomb calorimeter

qrxn + qbomb + qwater = 0

Question 36

qrxn + qbomb + qwater = 0
qrxn = unknown
qwater = *
qbomb = *
Cbomb = * of the bomb in *

Answer 36

qwater = mwater Cwater ΔT
qbomb = Cbomb ΔT

heat capacity in J/K

Question 37

How to calculate for ΔrH°

Answer 37

1. Using bond energies
2. Using Hess’s Law
3. Using heats of formation

Question 38

Bond energy
During a chemical reaction, reactant bonds are broken
and product bonds are made.
Breaking bonds requires energy

Making bonds releases energy

Answer 38

(endothermic, BE > 0)

exothermic, BE < 0

Question 39

Using bond energy theorem, how to compute for

ΔrH°?

Answer 39

ΔrH° = Σ𝐵𝐸 − Σ𝐵𝐸

Question 40

Breaking bonds requires energy : endothermic, *
Making bonds releases energy : exothermic, *
If bonds are stronger in products than reactants,
ΔrH° is *
If bonds are stronger in reactants than products,
ΔrH° is *

Answer 40

BE > 0
BE < 0
negative
positive

Question 41

if a reaction is the sum of two or more other
reactions, ΔrH° for the overall process is the
sum of the ΔrH° values of those reactions

Answer 41

Hess’s law

Question 42

regardless of the multiple stages or steps of a
reaction, the total enthalpy change for the
reaction is the sum of all changes
a manifestation that enthalpy is a *

Answer 42

skl HAHAHAHA
state
function!

Question 43

àenthalpy change for the formation of 1 mol
of a compound directly from its component
elements in their standard states

Answer 43

STANDARD MOLAR ENTHALPY OF FORMATION, 𝚫fH0

Question 44

ΔfH0 for an element in its * state is zero

Answer 44

standard

Question 45

ΔfH0 can often be used to compare

* of related compounds

Answer 45

stabilities

Question 46

enthalpy change for a reaction, ΔrH0, under standard
conditions may be calculated from ΔfH0 values
equation:
the equation is a consequence of the
definition of ΔfH0 and Hess’s Law

Answer 46

ΔrH° = ΣnΔfH° − ΣnΔfH°

Question 47

is the reaction product- or reactant-favored at equilibrium?
LOOK AT THE ΔrH0 VALUE!
product-favored = *
reactant-favored = *

Answer 47

product-favored = negative ΔrH0 (exothermic)
reactant-favored = positive ΔrH0 (endothermic)