Thermochemistry Flashcards

1
Q

potential energy

A

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

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2
Q

chemical energy

A

energy that can be released through a chemical reaction

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3
Q

kinetic energy

A

energy associated with movement

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4
Q

thermal energy

A

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

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5
Q

covalent bonds

A

bonds formed due to a shared pair of electrons

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6
Q

surroundings

A

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

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7
Q

reaction system

A

a mixture of reactants and products undergoing a reaction

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8
Q

open system

A

system that can exchange both energy and matter with its surroundings

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9
Q

closed system

A

system that can exchange energy but not matter with its surroundings

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10
Q

isolated system

A

system that cannot exchange energy or matter with its surroundings

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11
Q

temperature

A

a measure of thermal energy

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12
Q

state function

A

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

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13
Q

heat

A

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

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14
Q

work

A

the energy needed to move against a force.

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15
Q

enthalpy

A

the measurement of energy in a thermodynamic system

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15
Q

enthalpy change

A

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

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16
Q

first law of thermodynamics

A

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

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17
Q

endothermic reaction

A

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.

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18
Q

exothermic reaction

A

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.

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19
Q

bond dissociation energy

A

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

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20
Q

energy profile

A

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

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21
Q

activation energy

A

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.

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22
Q

standard enthalpy change

A

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

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23
Q

specific heat capacity

A

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

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24
Q

equation for heat of reaction

A

heat = mass * specific heat capacity * change in temperature

q = m * c * delta T

25
Q

change in enthalpy

A

heat of reaction divided by moles

delta H = q/moles

26
Q

Bond enthalpy

A

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

27
Q

homolytic fission

A

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

28
Q

heterolytic fission

A

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

29
Q

Hess’s law

A

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

30
Q

standard enthalpy change of combustion

A

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

31
Q

hydrocarbon

A

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

32
Q

standard heat of formation

A

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.

33
Q

ionization energy

A

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

34
Q

enthalpy of atomization

A

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

35
Q

electron affinity

A

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

36
Q

Lattice enthalpy

A

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

37
Q

Oxidation

A

loss of electrons

38
Q

Reduction

A

gain of electrons

39
Q

Redox reaction

A

one atom loses electrons, while the other gains electrons

40
Q

incomplete combustion

A

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.

41
Q

greenhouse gas

A

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

42
Q

greenhouse effect

A

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

43
Q

biofuel

A

liquid fuels derived from renewable sources like plants and algae

44
Q

biological carbon fixation

A

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

45
Q

fermentation

A

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

46
Q

climate change

A

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

47
Q

primary voltaic cells

A

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

48
Q

secondary voltaic cell

A

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

49
Q

fuel cell

A

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.

50
Q

hydrogen fuel cell

A

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

51
Q

direct methanol fuel cell

A

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

52
Q

spontaneous

A

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

53
Q

nonspontaneous

A

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

54
Q

Equilibrium

A

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

55
Q

entropy

A

a measure of the disorder of a system

56
Q

second law of thermodynamics

A

heat always flows spontaneously from hotter to colder regions of matter

57
Q

standard entropy change

A

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

58
Q

standard entropy

A

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

59
Q

reaction quotient

A

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

60
Q

equilibrium constant

A

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