Lecture 2

Question 1

What is internal energy?

Answer 1

The SUM of the KINETIC and POTENTIAL energies of all the particles in the system.

Question 2

Equation for the change in the system’s internal energy:

Answer 2

ΔE= q + w

Question 3

What is the third law of thermodynamics?

Answer 3

ENTROPY is temperature DEPENDENT. If all the thermal motion of all molecules (kinetic energy) could be removed, a state called ABSOLUTE ZERO would occur.

Question 4

What is absolute zero?

Answer 4

0 KELVIN = -273.15° CELSIUS

Question 5

What is thermochemistry?

Answer 5

The study of energy changes accompanying a chemical reaction, so the AMOUNT of energy taken in or given out.

Question 6

What is enthalpy?

Answer 6

ENTHALPY is a measure of the amount of heat RELEASED or CONSUMED by a reaction..

Question 7

Thermodynamic Definition of Enthalpy:

Answer 7

H = E + PV
E = Energy of the system & P = pressure of the system & V = volume of the system

Question 8

When heat is released during a reaction what happens to ΔH and the relative stability of bonds?

Answer 8

Products > Reactants

ΔH < 0

Question 9

When heat is consumed during a reaction what happens to ΔH and the relative stability of bonds?

Answer 9

Reactants > Products

ΔH > 0

Question 10

When there is no heat change during a reaction what happens to ΔH and the relative stability of bonds?

Answer 10

Reactants = Products 
ΔH = 0

Question 11

What is the standard enthalpy of formation?

Answer 11

STANDARD ENTHALPY OF FORMATION is the change in enthalpy that accompanies the formation of one mole of a COMPOUND from its ELEMENTS with all substances in their standard STATES.

Question 12

What is the symbol for the standard enthalpy of formation?

Answer 12

∆Hfө.

Question 13

What is the standard enthalpy of formation of a PURE ELEMENT in its standard state is defined as?

Answer 13

Zero

Question 14

What does a bomb calorimeter study?

How does it do this?

Answer 14

Exothermic Reactions

Heat energy is transferred to raise the temperature of its surroundings (water).

Question 15

What is the Enthalpy Change equation for Calorimetry?

Answer 15

∆H = mCp∆T

Question 16

What does Hess’ Law state?

Answer 16

“The overall enthalpy change accompanying a chemical reaction is INDEPENDENT of the route taken in going from reactants to products.”

Question 17

When does Hess’ law only apply?

Answer 17

Same initial and final states of TEMPERATURE and PRESSURE are applied to the REACTANTS and PRODUCTS.

Question 18

Enthalpy Change equation Hess’ Law:

Answer 18

∆H = ΣHproducts - ΣHreactants

Question 19

How can the ∆H for a reaction can be calculated?

Answer 19

Heat of FORMATION of ALL REACTANTS and PRODUCTS (Hess’s Law).
BOND ENERGIES of INDIVIDUAL BONDS.
Calorimetry

Question 20

How do you calculate enthalpy changes using Hess’ law cycle?

Answer 20

1. Question- Equation
2. Balance it!
3. Information in Question to Construct Cycle.
4. Arrows
5. Answer

Question 21

What is the equation to workout HR (Bond Energies)?

Answer 21

HR = ΣHbroken +ΣHformed