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Chemistry AP > Thermochemistry > Flashcards

Thermochemistry Flashcards

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1
Q

what is thermochemistry?

A

the study of the energy changes associated with chemical reactions

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2
Q

what is the theoretical definition of heating and cool energy change?

A

speed of particle is increasing or decreasing. (Ek)

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3
Q

what is the theoretical definition of phase changes in energy change?

A

intermolecular bonds are breaking/ forming. (Ep)

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4
Q

what is the theoretical definition of chemical reactions in energy change?

A

intramolecular bonds are breaking/ forming. (Ep)

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5
Q

what is the theoretical definition of nuclear reactions in energy change?

A

intranuclear bonds are breaking/ forming. (Ep)

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6
Q

what are intermolecular bonds?

A

between two molecules

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7
Q

what are intramolecular bonds?

A

within a molecule

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8
Q

what are intranuclear bonds?

A

within the nuclear of an atom

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9
Q

what is specific heat capacity? what are the units?

A

the energy required to raise the temperature of one gram of a substance by 1 c. J/ g * C or KJ/ g * C

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10
Q

what is water (l) heat capacity?

A

4.19 J/ g * C

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11
Q

what formula is used for temperature change problems?

A

q= mcdeltat

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12
Q

what is energy?

A

the capacity to do work or to produce heat

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13
Q

what is the law of conservation of energy?

A

energy cannot be created nor destroyed, only transformed from one form to another.

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14
Q

what is constant in the universe?

A

total energy

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15
Q

what is potential energy?

A

energy due to position or composition

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16
Q

what is kinetic energy?

A

energy due to motion of the object and depends in the mass of the object and its velocity

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17
Q

what is heat?

A

involves the transfer of energy between 2 objects due to a temperature difference

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18
Q

what is work?

A

force acting over a distance

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19
Q

what is a state function?

A

a property that does not depend in any way on the system’s past or future, only on the present state

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20
Q

is energy a state function?

A

yes

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21
Q

what are not state functions?

A

work and heat

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22
Q

what is a system?

A

part of the universe on which we wish to focus attention

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23
Q

what is the surroundings?

A

includes everything else in the universe

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24
Q

what is an endothermic reaction?

A

where heat flow is into a system. it absorbs energy from the surroundings.

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25
Q

what is an exothermic reaction?

A

where energy flows out of the system. releases heat to the surroundings.

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26
Q

what must be equal in exo and endothermic reactions?

A

energy gained/ lost by surroundings must be equal to the energy lost/ gained by the system.

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27
Q

is freezing water exo or endo?

A

exo

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28
Q

what is the law of conservation of energy also called?

A

the first law of thermodynamics

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29
Q

what is internal energy?

A

the sum of the kinetic and potential energies of all the particles in the system. represented by delta E

30
Q

what is the equation for internal energy?

A

delta E = q + w

31
Q

what does q represent?

A

heat

32
Q

what does w represent?

A

work

33
Q

is q + or - when there is an endothermic reaction?

A

+

34
Q

is q + or - when there is exothermic reaction?

A

-

35
Q

when is work - ?

A

when the system does work on the surroundings

36
Q

when is work +?

A

when the surroundings do work on the system

37
Q

what is the formula for w?

A

-PdeltaV

38
Q

what is the formula for P?

A

P = F/ A

39
Q

what is 1 L x atm equal to in joules?

A
  1. 3 J
40
Q

what is enthalpy?

A

the total kinetic and potential energy of a system under constant pressure.

41
Q

what is the formula for total enthalpy change?

A

delta H = nH

42
Q

is delta H a state function or not?

A

state function

43
Q

what is delta H equal to at constant pressure?

A

q (heat)

44
Q

what delta H be the difference to?

A

H (products) - H (reactants)

45
Q

what is calorimetry?

A

the measurement of the transfer of heat into or out of a system during a chemical reaction or physical process

46
Q

what is the formula for calorimetry?

A

nH = - mcdeltaT

47
Q

what is H?

A

molar enthalpy

48
Q

what is molar heat capacity?

A

the energy required to raise the temperature of one mole of a substance by 1 degree C

49
Q

what happens when two solutions mixing results in a warmer solution?

A

there was an exothermic reaction

50
Q

what happens when two solutions mixing results in a cooler solution?

A

there was an endothermic reaction

51
Q

what are the equations for a bomb calorimeter?

A

q = -CdeltaT, and nH = -CdeltaT

52
Q

what are four ways to describe energy change?

A
  1. molar enthalpy (kJ/ mol)
  2. enthalpy changes = delta H (kJ)
  3. enthalpy in a balanced equation (kJ)
  4. enthalpy change in an Ep diagram
53
Q

what is Hf?

A

molar enthalpy of a formation

54
Q

on what side is the energy in an exothermic reaction?

A

product

55
Q

on what side is the energy in an endothermic reaction?

A

reactant

56
Q

what happens to exothermic reactions once initiated?

A

they tend to continue because the energy released allows more reactants to overcome the activation energy barrier

57
Q

describe exothermic Ep diagram.

A

notes

58
Q

what happens to an endothermic reaction if the input of energy is stopped?

A

an endothermic reaction requires a continuous input of energy because the energy released as reactants clear the Ea barrier is hot enough to pull more reactants over

59
Q

what is a standard enthalpy of formation?

A

the enthalpy change for the formation of one mole of a substance in its standard state from its constituent elements in their standard states

60
Q

what is the Hf for an element?

A

0 kJ

61
Q

why are most Hf values negative?

A

because the compounds are thermodynamically more stable than the elements they are composed of

62
Q

what is Hess’ law?

A

if a chemical reaction can be expressed as the algebraic sum of 2 or more chemical reactions, the enthalpy change for the overall chemical reaction is also the algebraic sum of the individual reaction

63
Q

what is the formula for Hess’ law short form?

A

delta H reaction = sum of nHf (product) - sum of nHf (reactant)

64
Q

what type of water is created in an open environment in combustion?

A

gaseous water

65
Q

what type of water is created in an enclosed environment in combustion? what is an example of the environment?

A

liquid water. bomb calorimeter

66
Q

what is thermal stability?

A

the tendency of a compound to resist decomposition when heated. the more heating required to decompose a compound, the more stable it is.

67
Q

when must energy be added to a system?

A

to break bonds

68
Q

when must energy be released from a system?

A

to form bonds

69
Q

what is the equation to find delta h using bond energies?

A

delta h = (the sum of n * D (bonds broken)) - (the sum of n * D (bonds formed))

70
Q

what does D represent?

A

bond energy per mole of bonds

71
Q

what sign is D?

A

always positive

Chemistry AP (4 decks)

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