Thermochemistry

Question 1

potential energy

Answer 1

energy stored due to an objects position relative to other objects, electric charge or internal stresses

Question 2

chemical energy

Answer 2

energy that can be released through a chemical reaction

Question 3

kinetic energy

Answer 3

energy associated with movement

Question 4

thermal energy

Answer 4

energy associated with movement of particles that is responsible for its temperature

Question 5

covalent bonds

Answer 5

bonds formed due to a shared pair of electrons

Question 6

surroundings

Answer 6

everything around the reaction such as the reaction flask and the room (what we can typically measure)

Question 7

reaction system

Answer 7

a mixture of reactants and products undergoing a reaction

Question 8

open system

Answer 8

system that can exchange both energy and matter with its surroundings

Question 9

closed system

Answer 9

system that can exchange energy but not matter with its surroundings

Question 10

isolated system

Answer 10

system that cannot exchange energy or matter with its surroundings

Question 11

temperature

Answer 11

a measure of thermal energy

Question 12

state function

Answer 12

a property whose value does not depend on the path taken to reach that specific value, examples: number of atoms in a molecule in solid, liquid or gas state

Question 13

heat

Answer 13

the amount of energy that is transferred from one system to its surroundings because of a temperature difference

Question 14

work

Answer 14

the energy needed to move against a force.

Question 15

enthalpy

Answer 15

the measurement of energy in a thermodynamic system

Question 15

enthalpy change

Answer 15

the amount of heat energy transferred during a chemical reaction at constant pressure.

Question 16

first law of thermodynamics

Answer 16

energy cannot be created or destroyed; it can only be converted from one form to another

Question 17

endothermic reaction

Answer 17

a chemical reaction that absorbs heat due to products storing more energy than the products. This causes the temperature of the immediate surroundings to lower. Enthalpy is positive.

Question 18

exothermic reaction

Answer 18

a chemical reaction that releases heat due to reactants storing more energy than the products. This causes the temperature of the immediate surroundings to rise. Enthalpy is negative.

Question 19

bond dissociation energy

Answer 19

the amount of energy needed to break apart one mole of covalently bonded gases into a pair of radicals

Question 20

energy profile

Answer 20

a theoretical representation of a chemical reaction or process as a single energetic pathway as the reactants are transformed into products.

Question 21

activation energy

Answer 21

the amount of free energy that must be added to go from the energy level of the reactants to the energy level of the transition state.

Question 22

standard enthalpy change

Answer 22

the enthalpy change that occurs when 1 mole of the substance is formed from its constituent elements in their standard states

Question 23

specific heat capacity

Answer 23

the amount of heat that must be added to one gram of the substance in order to raise its temperature by 1 degree K

Question 24

equation for heat of reaction

Answer 24

heat = mass * specific heat capacity * change in temperature q = m * c * delta T

Question 25

change in enthalpy

Answer 25

heat of reaction divided by moles delta H = q/moles

Question 26

Bond enthalpy

Answer 26

the enthalpy change when one mole of covalent bonds (in a gas) is broken under standard conditions. Bond breaking is endothermic and delta H is positive, bond building is exothermic and delta H is negative

Question 27

homolytic fission

Answer 27

a covalent bond breaks and one electron goes back to each atom

Question 28

heterolytic fission

Answer 28

a covalent bond breaks and both electrons in the bond go to one atom

Question 29

Hess's law

Answer 29

the enthalpy change accompanying a chemical reaction is independent of the pathway between the initial and final states

Question 30

standard enthalpy change of combustion

Answer 30

the enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions. (found by reactants-products!)

Question 31

hydrocarbon

Answer 31

a compound containing carbon and hydrogen only, named by mono-, di-, tri ... and end in -ane, -ene or -yne

Question 32

standard heat of formation

Answer 32

the enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions. Value is zero for elements in their standard state.

Question 33

ionization energy

Answer 33

the minimum amount of energy required to remove an electron from a gaseous atom. X(g) → X⁻ (g) + e⁻

Question 34

enthalpy of atomization

Answer 34

the enthalpy change when one mole of a gaseous atoms is formed from an element in its standard state X2(g) → 2X(g)

Question 35

electron affinity

Answer 35

the amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion. X(g) + e⁻ → X⁻ + energy

Question 36

Lattice enthalpy

Answer 36

the enthalpy change when one mole of ionic compound is broken apart into gaseous ions. AX(g) → A⁻ (g) + X+(g)

Question 37

Oxidation

Answer 37

loss of electrons

Question 38

Reduction

Answer 38

gain of electrons

Question 39

Redox reaction

Answer 39

one atom loses electrons, while the other gains electrons

Question 40

incomplete combustion

Answer 40

the burning of a substance in a limited supply of oxygen - when the substance is a hydrocarbon either carbon or carbon monoxide will be a product.

Question 41

greenhouse gas

Answer 41

consist of carbon dioxide, methane, ozone, nitrous oxide, chlorofluorocarbons, and water vapor. Absorb infrared radiation and trap heat in the atmosphere

Question 42

greenhouse effect

Answer 42

gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature.

Question 43

biofuel

Answer 43

liquid fuels derived from renewable sources like plants and algae

Question 44

biological carbon fixation

Answer 44

the process by which organisms convert inorganic carbon into organic compounds (ie, photosynthesis)

Question 45

fermentation

Answer 45

a biological process where organisms convert carbohydrates, such as sugars or starch, into acids or alcohols which can be used as fuels

Question 46

climate change

Answer 46

the change in earths climate due to man made factors such as the increase in atmospheric greenhouse gases like CO2, due to burning of fossil fuels

Question 47

primary voltaic cells

Answer 47

a cell that produces electricity through an irreversible chemical reaction, but cannot be recharged

Question 48

secondary voltaic cell

Answer 48

a rechargeable battery that can be recharged with electricity and reused many times

Question 49

fuel cell

Answer 49

a type of electrochemical cell that uses the reaction between fuel and an oxidizing agent to produce electrical energy directly. It uses a continuous supply of reactants from an external source.

Question 50

hydrogen fuel cell

Answer 50

A fuel cell uses the chemical energy of hydrogen for proton exchange to produce electrical energy

Question 51

direct methanol fuel cell

Answer 51

a fuel cell that converts the chemical energy of methanol into electricity (cheaper and more readily available than hydrogen fuel)

Question 52

spontaneous

Answer 52

a reaction that favors the formation of products at the conditions under which the reaction is occurring

Question 53

nonspontaneous

Answer 53

a reaction that favors the reactants at the conditions under which the reaction is occurring

Question 54

Equilibrium

Answer 54

a reversible chemical reaction in which no net change in the amounts of reactants and products occur

Question 55

entropy

Answer 55

a measure of the disorder of a system

Question 56

second law of thermodynamics

Answer 56

heat always flows spontaneously from hotter to colder regions of matter

Question 57

standard entropy change

Answer 57

the change in entropy change under standard conditions. If delta S is positive entropy has increased.

Question 58

standard entropy

Answer 58

the entropy of a substance at 100 kPa and 298K. Units are J K-1 mol -1

Question 59

reaction quotient

Answer 59

the ratio of the concentrations of the reactants and the products at any point in time.

Question 60

equilibrium constant

Answer 60

the ratio of the concentrations of the reactants and the products at equilibrium