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IB Chemistry HL > 5 energetics > Flashcards

5 energetics Flashcards

1
Q

define heat

A

transfer of energy between objects of different temperature

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2
Q

what is thermal equilibium

A

when two objects reach the same temperature and so no more energy is transferred

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3
Q

what is enthalpy

A

heat content of the system

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4
Q

ΔHƟ meaning

A

enthalpy change under standard conditions

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5
Q

what are standard conditions

A

pressure of 100,000 Pa

temperature of 298K

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6
Q

define temperature

A

average kinetic energy of the particles in a substance

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7
Q

what is absolute temperature proportional to

A

average kinetic energy of particles in a sample

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8
Q

what is absolute temp

A

0K, where the particles have the least amount ofkinetic energy

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9
Q

what is an open system

A

where matter and energy can move freely between the system and surroundings

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10
Q

what is a closed system

A

where enrgy or matter is not exchanged with the surroundings

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11
Q

what do thermochemical equations show

A

enthalpy change of reaction

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12
Q

q =

A

mc∆T

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13
Q

what is q

A

heat absorbed or released in J

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14
Q

what is c

A

the specific heat capacity of the solution in J g−1 °C−1 or J g−1 K−1

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15
Q

what is m

A

is the mass of solution in g

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16
Q

what is ∆T

A

is the change in temperature in oC or K

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17
Q

specific heat capacity def

A

the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius or one kelvin. The units of specific heat capacity are either joules per gram per degree Celsius (J g−1 °C−1) or joules per gram per kelvin (J g−1 K−1).

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18
Q

what does ΔHn mean

A

enthalpy change of neutralisation

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19
Q

what is enthalpy change of neutralisation

A

the enthalpy change when an acid and base react together to form one mole of water.

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20
Q

how can enthalpy changes be calcualted

A

from their effect on the temperature of their surroundings

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21
Q

what is heat

A

form of energy

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22
Q

what is temperature

A

a measure of the average kinetic energy of the partiles

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23
Q

when is enthalpy change negative

A

exothermic reaction

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24
Q

when is enthalpy change positive

A

endothermic reaction

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25
what is the equation deductible from a hess law diagram
that overall enthalpy change will be enthalpy change 1 + enthalpy change 2 enthalpy change for a reaction is the same regardless of the route taken
26
overall enthalpy change of formation =
sum of enthalpy change of products - sum of enthalpy change of reactants
27
what is hess' law
the enthalpy change for a reaction is independent of the route taken
28
overall enthalpy change of combustion
sum of enthalpy change of reactants - sum of enthalpy change of products
29
Pre combustion methods
Removing sulfur before the coal is combusted
30
Post combustion methods
Removing the sulfur oxides from exhaust gases once they have been formed by reacting with a base
31
What is hydrodesulfurisation
Pre combustion method where the sulfur is removed from refined petroleum. The sulfur is removed from the product in the form of hydrogen sulfide (H2S)
32
What is flue gas desulfurization
Sulfur dioxide levrls in flue gases reduced by passing them through a flue gas desulfurization tower or scrubber
33
Equation of flue gas desulfurization
CaO + SO2 --> CaSO3 | CaCO3 + SO2 --> CaSO3 + CO2
34
What do catalytic converters do
Remove NOx
35
heat is defined as
the transfer of energy between objects of different temperature
36
once two objects reach the same temperature, which is known as thermal equilibrium,
no more energy will be transferred
37
temperature is defined as
the average kinetic energy of the particles in a substance
38
adv of polystyrene as a calorimeter are
Polystyrene is a good heat insulator, therefore, it reduces heat loss to the surroundings The expanded polystyrene cup absorbs very little heat itself, so there is no need to calculate the heat absorbed by the calorimeter.
39
q =
mc∆T
40
what is q
the heat absorbed or released in J
41
what is c
the specific heat capacity of the solution in J g−1 °C−1 or J g−1 K−1
42
ΔHn
enthalpy change of neutralisiation
43
ΔHƟc
molar enthalpy of combustion or standard enthalpy of combustion
44
what is molar enthalpy of combustion
the enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions.
45
limitations of calcualating enthalpy changes in a school labratory
Heat loss to the surroundings and heat absorbed by the calorimeter Incomplete combustion of the fuel Assumptions made about the specific heat capacity and density of aqueous solutions.
46
what is perpetual motion
motion that continues indefinitely without any external source of energy.
47
first law of thermodynamics
energy can neither be created nor destroyed
48
hess's law
the total enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place, as long as the initial and final conditions are the same.
49
ΔH⦵f
enthalpy change of formation
50
what is enthalpy change of formation
the enthalpy change when one mole of a compound is formed from the elements in their standard states under standard conditions.
51
what do enthalpy change of formation values indicate
the stablity of compounds in relation to their elements
52
the more negative enthalpy change of formation values are...
the more stable they are
53
ΔH⦵c =
ΣΔH⦵c (reactants) − ΣΔH⦵c (products)
54
ΔH⦵f =
ΣΔH⦵f (products) − ΣΔH⦵f (reactants)
55
the standard enthalpy change of formation of an element in its standard state is
zero.
56
breaking bonds is
endothermic
57
making bonds is
exothermic
58
what is bond enthalpy
energy required to beak a chemical bond
59
why are bond enthalpy values always positive
because they refer to bonds being broken
60
what is average bond enthalpy
enthalpy change when one mole of bonds are broken in the gaseous state is averaged for the same bond in similar compounds
61
ΔH = | bonds
ΣE(bonds broken) − ΣE(bonds formed)
62
ΔH = | r and p
Σ(bond enthalpies of reactants) – Σ(bond enthalpies of products)

IB Chemistry HL (12 decks)

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