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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
Q

what is the equation deductible from a hess law diagram

A

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
Q

overall enthalpy change of formation =

A

sum of enthalpy change of products - sum of enthalpy change of reactants

27
Q

what is hess’ law

A

the enthalpy change for a reaction is independent of the route taken

28
Q

overall enthalpy change of combustion

A

sum of enthalpy change of reactants - sum of enthalpy change of products

29
Q

Pre combustion methods

A

Removing sulfur before the coal is combusted

30
Q

Post combustion methods

A

Removing the sulfur oxides from exhaust gases once they have been formed by reacting with a base

31
Q

What is hydrodesulfurisation

A

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
Q

What is flue gas desulfurization

A

Sulfur dioxide levrls in flue gases reduced by passing them through a flue gas desulfurization tower or scrubber

33
Q

Equation of flue gas desulfurization

A

CaO + SO2 –> CaSO3

CaCO3 + SO2 –> CaSO3 + CO2

34
Q

What do catalytic converters do

A

Remove NOx

35
Q

heat is defined as

A

the transfer of energy between objects of different temperature

36
Q

once two objects reach the same temperature, which is known as thermal equilibrium,

A

no more energy will be transferred

37
Q

temperature is defined as

A

the average kinetic energy of the particles in a substance

38
Q

adv of polystyrene as a calorimeter are

A

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

q =

A

mc∆T

40
Q

what is q

A

the heat absorbed or released in J

41
Q

what is c

A

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

42
Q

ΔHn

A

enthalpy change of neutralisiation

43
Q

ΔHƟc

A

molar enthalpy of combustion or standard enthalpy of combustion

44
Q

what is molar enthalpy of combustion

A

the enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions.

45
Q

limitations of calcualating enthalpy changes in a school labratory

A

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
Q

what is perpetual motion

A

motion that continues indefinitely without any external source of energy.

47
Q

first law of thermodynamics

A

energy can neither be created nor destroyed

48
Q

hess’s law

A

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
Q

ΔH⦵f

A

enthalpy change of formation

50
Q

what is enthalpy change of formation

A

the enthalpy change when one mole of a compound is formed from the elements in their standard states under standard conditions.

51
Q

what do enthalpy change of formation values indicate

A

the stablity of compounds in relation to their elements

52
Q

the more negative enthalpy change of formation values are…

A

the more stable they are

53
Q

ΔH⦵c =

A

ΣΔH⦵c (reactants) − ΣΔH⦵c (products)

54
Q

ΔH⦵f =

A

ΣΔH⦵f (products) − ΣΔH⦵f (reactants)

55
Q

the standard enthalpy change of formation of an element in its standard state is

A

zero.

56
Q

breaking bonds is

A

endothermic

57
Q

making bonds is

A

exothermic

58
Q

what is bond enthalpy

A

energy required to beak a chemical bond

59
Q

why are bond enthalpy values always positive

A

because they refer to bonds being broken

60
Q

what is average bond enthalpy

A

enthalpy change when one mole of bonds are broken in the gaseous state is averaged for the same bond in similar compounds

61
Q

ΔH =

bonds

A

ΣE(bonds broken) − ΣE(bonds formed)

62
Q

ΔH =

r and p

A

Σ(bond enthalpies of reactants) – Σ(bond enthalpies of products)

IB Chemistry HL (12 decks)

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