Energy, Enthalpy, and Thermochemistry

Question 1

Energy

Answer 1

Capacity to do work/ produce heat

Question 2

Law of conservation of energy

Answer 2

Energy can be converted from one form to another, but it can neither be created or destroyed

Question 3

Thermochemistry

Answer 3

the study and measurement of heat evolved or absorbed during chemical reactions

Question 4

2 types of energy

Answer 4

Kinetic: energy due to the motion of an object
Potential: energy due to position or composition

Question 5

Temperature

Answer 5

Reflects the random motion of particles

Question 6

Heat

Answer 6

energy transferred due to a temperature difference

Question 7

Work:

Answer 7

Force acting over a distance

Question 8

State function

Answer 8

a property of a system that depends only on its present state
I.e it is path independent

Question 9

State function include

Answer 9

• internal energy
• temperature
• pressure
• Volume
• Enthalphy

Question 10

Path-dependent properties include

Answer 10

• Work

- Heat

Question 11

Exothermic reaction

Answer 11

Heat is released, heat in the product

Question 12

Endothermic reaction

Answer 12

Heat is absorbed, Heat in the reactant

Question 13

Internal energy

Answer 13

Sum of the kinetic and potential energy of all particles

Question 14

Internal energy formula

Answer 14

change in E = q + w
q>0 E system increase (Endothermic)
q<0 E system decrease (exothermic)

Question 15

Internal energy formula (work)

Answer 15

W>0 E system increase -> work is done to the system

W<0 E system decrease -> system performs work on the surrounding

Question 16

Units of energy

Answer 16

J=Kgm^2/s^2
Heat = energy = J
Work = Energy = J

Question 17

Common type of work in gases

Answer 17

w= -P x change in V
Expansion: (w < 0) work done by the gas
Compression: (w>0) work done on the gas

Question 18

Expansion

Answer 18

(w < 0) work done by the gas

change in V > 0 -> w < 0

Question 19

Compression

Answer 19

change in V < 0 -> w > 0

(w>0) work done on the gas

Question 20

Enthalpy

Answer 20

Measure of heat
H= E+PV
A change in enthalpy is amount of heat (q) given off or absorbed at a constant pressure

Question 21

Molar heat capacity

Answer 21

Energy required to raise the temp of 1 mol of that substance by 1K
3/2R = valid for monoatomic gas at constant volume

Question 22

Constant pressur molar heat capacity (Cp)

Answer 22

Cp = (3/2)R + R = Cv + R = (5/2)R

Question 23

3 ways of molecule can accommodate heat energy

Answer 23

1. Translational
2. Vibrational
3. Rotational

Question 24

Calorimetry

Answer 24

Science of measuring heat

Based on observations of temperature changes when a body absorbed or discharges energy as heat

Question 25

Calorimeter

Answer 25

Device used to determine the heat associated with chemical reactions

Question 26

Heat capacity

Answer 26

Represent the amount of energy necessary to increase the temp by 1 C or 1 K
= Heat absorbed/ Increase in temp

Question 27

Two types of calorimeters ( constant pressure )

Answer 27

Measure change in enthalpy

Question 28

Two types of calorimeters (Constant Volume)

Answer 28

Measure changes in internal energy

bomb calorimeter

Question 29

Hess’s Law of constant Heat Summation

Answer 29

Indirect determination of change in H

H is a state function: path independent

Question 30

Standard states

Answer 30

For a compound

• gas = 1atm
• Liquid/solid= pure substance
• solution = 1M

For element

• 1atm
• usually 25 C