Thermodynamics

Question 1

What is the second law of thermodynamics?

Answer 1

The entropy of an isolated system tends to increase

Question 2

What is the third law of thermodynamics

Answer 2

The entropy of a perfect crystal approaches zero as the absolute temperature approaches zero

Question 3

What is the zeroth law of thermodynamics

Answer 3

When two objects are separately in thermal equilibrium with a third object, they are also in thermal equilibrium with each other

Question 4

Define the standard molar enthalpy of formation.

Answer 4

The enthalpy change when one more of substance is formed from its constituent elements under standard conditions. All products and reactants in their standard states.

Question 5

Define the standard molar enthalpy of combustion.

Answer 5

The enthalpy change when one mole of substance is burned completely in oxygen under standard conditions

Question 6

Define the standard molar enthalpy of atomisation.

Answer 6

The enthalpy change when one mole of substance decomposes to form gaseous atoms under standard conditions

Question 7

Define the standard molar enthalpy of first ionisation.

Answer 7

The enthalpy change when one mole of electrons is removed from one mole of gaseous atoms under standard conditions

Question 8

Define the standard molar enthalpy of first electron affinity.

Answer 8

The negative enthalpy change when one mole of electrons is added to one mole of gaseous atoms under standard conditions.

Question 9

Define the standard molar enthalpy of fusion

Answer 9

The enthalpy change when one more of substance melts under standard conditions

Question 10

Define the standard molar enthalpy of vaporisation.

Answer 10

The enthalpy change when one mole of a substance vaporises under standard conditions

Question 11

Define the standard lattice enthalpy

Answer 11

The enthalpy change when a crystalline ionic solid is formed from its constituent ions in the gas phase under standard conditions

Question 12

Define Hess’ law

Answer 12

The enthalpy change for any process is independent of the pathway required to complete the process provided the final and initial reaction conditions are the same.

Question 13

What is the first law of thermodynamics?

Answer 13

The change in internal energy, U, of a system is equal to the amount of heat supplied to the amount of heat supplied to the system plus the amount of work performed on the system.

Question 14

Define the term phase

Answer 14

It is a specific state of matter that is uniform throughout in composition and physical.

Question 15

Define phase boundary

Answer 15

A phase boundary traces the pressures and temperatures at which two phases are in equilibrium

Question 16

What is the phase rule and explain its components

Answer 16

*For any given system with C components and P phases the degrees of freedom F are given by
F=C-P+2
-the degrees of freedom, F is the number of intensive variables that can be changed independently without disturbing the number of phases in equilibrium.

Question 17

Define the term reaction mechanism

Answer 17

It is the sequence of elementary molecular events that lead from reactants to products

Question 18

Define the term molecularity

Answer 18

For an elementary reaction step it is the number of species coming together to react

Question 19

Describe the stopped flow method.

Answer 19

• reactants are rapidly mixed by flowing them into a cell using pumps
• the flow is then quickly stopped and the progress of the reactant is monitored spectrophotometerically

Question 20

Describe the continuous flow method.

Answer 20

• reactants are continuously flowed through the mixing chamber into a long tube
• and a movable spectrophotometer measures the concentrations as a function of distance down the tube

Question 21

Describe flash photolysis

Answer 21

• reaction is initiated via short pulse of light,

- the results are then probed using a weaker second beam of light to measure the spectra reactants and products

Question 22

Define the term phase

Answer 22

It is a specific state of matter that is uniform throughout in composition and physical.

Question 23

Define phase boundary

Answer 23

A phase boundary traces the pressures and temperatures at which two phases are in equilibrium

Question 24

What is the phase rule and explain its components

Answer 24

*For any given system with C components and P phases the degrees of freedom F are given by
F=C-P+2
-the degrees of freedom, F is the number of intensive variables that can be changed independently without disturbing the number of phases in equilibrium.