Thermochemistry

Question 1

What is gibbs free energy?

Answer 1

Gibbs free energy combines enthalpy and entropy into a single value. This quantity is the energy
associated with a chemical reaction that can be used to do work.

Question 2

How does Gibb’s energy affect spontaneity?

Answer 2

Spontaneity decreases with gibbs energy.

Question 3

What is the formula for gibbs energy?

Answer 3

ΔGo = −nF Ecello

Where:
ΔGo is the standard free energy change
n is the number of transferred electrons
Eo is the standard cell potential
F is the Faraday constant = 96500 C mol-1

Question 4

What is Faradays constant?

Answer 4

96500 C mol-1

Question 5

Formula for Nernst equation

Answer 5

E = Eo − (RT/ nF ) ln ( ([Product]) / [Reactant] )

E is the cell potential
Eo is the standard cell potential
R is the universal gas constant = 8.314 J/K/mole
T is the temperature
n is the number of transferred electrons
F is the Faraday constant = 96500 C mol-1
.

Question 6

What is the universal gas constant?

Answer 6

8.314 J/K/mole

Question 7

What are the main types of systems in thermochemistry?

Answer 7

Isolated, closed, and open.

Question 8

What is an isolated system?

Answer 8

No anything in or out.

Question 9

What is closed system?

Answer 9

No exchange of matter

Question 10

What are thermodynamic properties?

Answer 10

Thermodynamic properties are defined as characteristic features of a system, capable of
specifying the system’s state.

Question 11

Examples of thermodynamic properties

Answer 11

1. Pressure
2. Temperature
3. Volume
4. Entropy
5. Internal energy
6. Enthalpy
7. Gibbs function
8. Helmholtz functions.

Question 12

How many types of physical properties of a system are there?

Answer 12

2. Intensive and extensive.

Question 13

What are intensive properties?

Answer 13

Intensive properties are properties that do not depend on the quantity of matter.

Question 14

What are extensive properties?

Answer 14

Extensive properties are properties whose value depends on the mass of the
system.

Question 15

What are examples of physical properties of a system.

Answer 15

Helmholtz free energy (F)
Gibbs free energy (G)
Enthalpy (H)
Internal energy (U)
Entropy (S)
Volume (V)
Temperature (T)
Pressure (P)

Question 16

What is enthalpy?

Answer 16

Determines the capability of a system to do work and release heat.

Question 17

What is gibbs energy?

Answer 17

The thermodynamic potential that measures the maximum or reversible work by a thermodynamic system. Determines the feasibility of a reaction.

Question 18

What is Helmholtz free energy?

Answer 18

The thermodynamic potential that measures useful work done by a closed thermodynamic
system

Question 19

How many types of thermodynamic processes are there?

Answer 19

4. Isobaric, isochoric, isothermal, adiabatic

Question 20

What is an isobaric process?

Answer 20

• An isobaric process, during which the system’s pressure does not change.

Question 21

What is isothermal process?

Answer 21

• An isothermal process, during which the system’s temperature remains constant.

Question 22

What is adiabatic process?

Answer 22

• An adiabatic process, during which no heat is transferred to or from the system.

Question 23

What is isochoric process?

Answer 23

• An isochoric process, during which the system’s volume does not change.

Question 24

What is formula for enthalpy change?

Answer 24

ΔH = ΔU + ΔPV

where
H = Enthalpy
U = Internal energy
P = Pressure
V = Volume

Question 25

What are the main types of enthalpy changes?

Answer 25

• Enthalpy change of formation.
• Enthalpy change of neutralization.
• Enthalpy change of combustion.
• Enthalpy change of reaction (generalized)

Question 26

What is standard enthalpy change of formation?

Answer 26

The standard enthalpy of formation is defined as the change in enthalpy when one mole
of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its
pure elements.

Question 27

What is enthalpy change of reaction?

Answer 27

The standard enthalpy of reaction is the enthalpy change that occurs in a system when a
chemical reaction transforms one mole of matter under standard conditions (1 atm of
pressure and 298 K). Generalized term.

Question 28

What is Hess’s law?

Answer 28

Enthalpy change for a reaction is independent of the number of ways a product can be
obtained, if the initial and final conditions are the same.

Question 29

What is the second law of thermodynamics?

Answer 29

In a spontaneous process the
entropy of the universe
increases.

Question 30

Formula for Gibb’s free energy

Answer 30

ΔG=ΔH−TΔS

Question 31

What do endogornic and exogornic reactions relate to

Answer 31

Gibbs energy

Question 32

What is a solution?

Answer 32

A solution is a homogeneous mixture of two or more substances and can
either be in the gas phase, the liquid phase, the solid phase.

Question 33

Factors affecting solubility

Answer 33

• Nature of solute:
Like dissolves like.

• Temperature:
In case of liquids and solids, solubility increases with an
increase in temperature. For gases, it decreases.

• Pressure:
Does not affect most solids and liquids. In case of gases,
solubility is directly proportional to pressure

Question 34

What is Henry’s law?

Answer 34

Cg =kPg

where C is solubility, P is pressure and k is
proportionality constant that depends on temperature and nature of solvent

Question 35

What is molarity?

Answer 35

Moles of solute/ Liter of solution

Question 36

What is molality?

Answer 36

Moles of solute/ kg of solution

Question 37

What is mole fraction?

Answer 37

Moles of solute/ total moles in solution

Question 38

What is parts per million?

Answer 38

(Mass of solute/ mass of solution)*10^6