Thermochemistry (7)

Question 1

Isolated

Answer 1

The system cannot exchange energy (heat and work) or matter with the surrounding

ex: insulated bomb calorimeter

Question 2

Closed

Answer 2

The system can exchange energy (heat and work) but not matter with the surrounding;
ex: a steam radiator

Question 3

Open

Answer 3

The system can exchange both energies (heat and work) and matter with the surrounding

ex: a pot of boiling water

Question 4

First law of Thermodynamics

Answer 4

ΔU = Q - W

ΔU = change in internal energy of the system
Q = heat added TO THE system
W = work done BY THE system

Question 5

Isothermal Process

Answer 5

Occurs when the temperature is constant
Constant Temperate = Constant ΔU = ΔU = 0

Q = W

Hyperbolic curve of Pressure vs. Volume graph

Question 6

Adiabatic Process

Answer 6

Occurs when no heat is exchanged between the system and the environment, so Q = 0

ΔU = -W

Temperature is not constant

Question 7

Isobaric Process

Answer 7

occurs when the pressure of the system is constant.

Pressure vs. Volume graph line appears flat line b/c Pressure is constant

Question 8

Isovolumetric (Isochoric) proccess

Answer 8

No change in volume, no work is performed in such a process.
ΔU = Q (change in internal heat is equal to the heat added to the system)

Pressure vs. Volume graph line appears verticle line

Question 9

State functions

Answer 9

When I’m under PRESSURE, and feeling DENSE, all I want to do is watch TV and get HUGS.

• Pressure (P)
• density (p)
• Temperature (T)
• Volume (V)
• Enthalpy (H)
• Internal energy (U)
• Gibbs free energy (G)
• Entropy (S)

Question 10

Standard conditions vs. STP

Answer 10

Standard conditions: 25 °C (298K) , 1atm pressure, 1M concentration

STP: 0 °C (273K) , 1atm pressure

Question 11

Heat

Answer 11

the specific form of energy that can enter or leave a system

Question 12

Temperature

Answer 12

the measure of the average kinetic energy of the particles in a system.

Question 13

Exothermic and Endothermic

Answer 13

Exothermic = -ΔH Enthalpy

Endothermic = + ΔH Enthalpy

Question 14

Calorimetry

Answer 14

process of measuring transferred heat

Question 15

Heat/energy

J vs Cal Conversion

Answer 15

1cal = 4.184J

Question 16

Heat transfer equation

Answer 16

q = mCΔT

Question 17

Standard enthalpy of formation

Answer 17

enthalpy required to produce one mole of a compound from its element in their standard states.

Question 18

Standard enthalpy of reaction

Answer 18

enthalpy change accompanying a reaction being carried out under the standard condition.

ΔH°rxn = ΣH°f, products - ΣH°f, reactants

Question 19

Hess’s Law

Answer 19

total change in potential energy of a system is equal to the change of potential energies of the individual step of the process.

Enthalpy changes in reactions are additive.

ΔH = ΔH1 + ΔH2 + ΔH3

Question 20

Bond Energy

Answer 20

ΔH°rxn = ΔH bond broken - ΔH bonds formed

bond breakage is endothermic
the bond formation is exothermic

\+ΔH = total energy absorbed
-ΔH = total energy released

Question 21

Second law of Thermodynamics

Answer 21

energy spontaneously disperses from being localized to becoming spread out. disorder and entropy.

ΔS universe = ΔS system + ΔS surrounding > 0

ΔS = ΣS°f, products - ΣS°f, reactants

Question 22

Entropy

Answer 22

the measure of the spontaneous dispersal of energy at a specific temperature.

S = Qrev / T

Question 23

Gibbs free energy

Answer 23

ΔG = ΔH - TΔS
Goldfish are (equal)  Horrible without (minus)  Tartar Sauce

If ΔG = 0 , the system is in a state of equilibrium,
ΔH = TΔS

Question 24

Exergonic

Answer 24

The movement towards the equilibrium. When energy released.
ΔG < 0
spontaneous

Question 25

Endergonic

Answer 25

The movement away from the equilibrium
ΔG > 0
non-spontaneous

Question 26

Signs of ΔH and ΔS corresponding to Temperature

Answer 26

ΔH (+) ΔS (+) Spontaneous at High T
ΔH (+) ΔS (-) Nonspontaneous at all T
ΔH (-) ΔS (+) Spontaneous at all T
ΔH (-) ΔS (+) Spontaneous at low T

Question 27

Standard Gibbs free energy formula

Answer 27

ΔG = ΣG°f, products - ΣG°f, reactants

Question 28

Free energy, Keq, and Q

Answer 28

ΔG°rxn = -RT lnKeq

greater the Keq value, more negative the Gibbs free energy and leads to spontaneous rxn.

ΔGrxn = ΔG°rxn + RTlnQ = RTln Q/Keq

If the Q/Keq ratio is less than one, then the Gibbs free energy is negative, spontaneous rxn.
Q < Keq –> spontanous
Q > Keq –> non-spontanous