Chapter 2- Review II

Question 1

What is heat?

Answer 1

The flow of energy caused by a temperature difference

Question 2

What is the system and the surroundings?

Answer 2

The system is the object/solution being studied

The surroundings is anything with which the system can exchange energy

Question 3

What is the first law of thermodynamics?

Answer 3

The total energy in the universe is constant

Question 4

What is the internal energy?
What is it’s symbol?
Equation for finding change in internal energy?
How does it compare form a system to its surroundings

Answer 4

The sum of the kinetic and potential energies of all the particles that compose a system
E or ΔΕ
ΔE=q + w
Esys = -Esurr

Question 5

When is heat, work and internal energy positive?

Answer 5

Heat (q)- when system gains thermal energy
Work (w)- when work is done on the system
ΔE- when energy flows into the system

Question 6

What is the heat capacity?
Specific heat capacity?
Molar heat capacity?

Answer 6

Heat capacity- heat required to change temp by 1 degree C
Specific- heat required to change temp by 1 degree C of 1 gram of substance
Molar- heat required to change temp by 1 degree C of 1 mole of the substance

Question 7

What is the formula for finding heat using heat capacity and change in temp?
How about for a bomb calorimeter?

Answer 7

Q = C (ΔT)
Or
q= m x Cs x ΔT

Bomb
Qcal = Ccal x ΔT

Question 8

How does the heat of the surroundings differ from the heat of the system?

Answer 8

qsys = -qsurr
C(ΔT)sys= -C(ΔT)surr

Question 9

What is the formula for work?

What’s re the signs when gas expands?

Answer 9

W= -PΔV

ΔV= + 
W= - when gas expands

Question 10

What is the internal energy equation for heat at a constant volume?

Answer 10

ΔErxn = qv

Qv= heat at constant volume

Question 11

How does the heat from a calorimeter compare to the heat of the reaction?
How do you find the internal energy of the reaction when you have moles and qcal?

Answer 11

Qcal = qsurr = -qrxn

Qrxn= nΔErxn
Then ΔErxn = qrxn/n

Question 12

What is enthalpy and its formula?

What is the formula with heat at a constant pressure?

Answer 12

The sum of the internal energy and the product of its pressure and volume
ΔH=ΔE+PΔV

Constant pressure
ΔΗ=(qp+w) + (-w)
ΔΗ= qp (heat at constant pressure)

Question 13

How does enthalpy represent exothermic and endothermic reactions?

Answer 13

ΔH= -
Heat is being released by system, exothermic
ΔΗ= +
Heat is being absorbed by the system, Endothermic

Question 14

What do we use to measure ΔHrxn?

What is the formula?

Answer 14

Coffee cup calorimeter
Qsoln=msoln x Cssoln x ΔT

qrxn=-qsoln=-qcal

Question 15

What is the standard state for gas, liquid of solid, and substance in a solution?

Answer 15

Gas- pure gas at 1 atm
Liquid of solid- pure substance in most stable form at 1 atm and temperature of interest (often 25C)
substance in solution- concentration of 1M

Question 16

What is the standard enthalpy change?

Answer 16

Change in enthalpy for a process when all reactants and products are in their standard states
ΔH*
(degree)

Question 17

What is the standard enthalpy of formation for a pure compound and a pure element in its standard state?

Answer 17

Pure compound- change in enthalpy when 1 mole of compound forms from the elements in their standard states
Pure element- ΔH*f = 0

Question 18

What does volatile mean?

Answer 18

Liquids that vaporize easily

Question 19

What is the heat of vaporization?

Its symbol?

Answer 19

Amount of heat required to vaporize one mole of liquid to gas
ΔHvap
Always positive since vaporization is endothermic

Question 20

What is vapor pressure?

Answer 20

The pressure of a gas in dynamic equilibrium with its liquid

Question 21

What is the boiling point and the normal boiling point of a liquid?

Answer 21

Boiling point- the temperature at which its vapor pressure equals the external pressure
Normal boiling point- the temperature at which its vapor pressure equals 1atm

Question 22

What is the heat of fusion?

Answer 22

The amount of heat required to melt 1 mole of a solid

ΔHfus is positive since melting is endothermic

Question 23

What is ΔHsub equal too?

Answer 23

ΔHsublimation= ΔHvaporization + ΔHfusion

Also is equal to -ΔHdeposition

Question 24

What is -ΔHdeposition equal to?

Answer 24

-ΔHdeposition = -ΔHcondensation + (-ΔHfreezing)

Question 25

What is Clausius-Clapeyron equation involving change in pressure, change in temp, R, -ΔHvaporization, and ln?

Answer 25

ln(P2/P1) = -ΔHvaporization/R
(1/T2 - 1/T1)

Use antilog if you need to find pressure

Question 26

What is exothermic vs endothermic?

Answer 26

Exo-releases heat, raises temp of surroundings
dE is negative
Endo- absorbs heat, cools surroundings
dE is positive