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chemistry > energetics > Flashcards

energetics Flashcards

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1
Q

what are the standard conditions?

A

298K, 1 bar and 1moldm^-3

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2
Q

what is the enthalpy change of reaction?

A

it is the energy change of a given stoichiometric equation at the given temperature and pressure

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3
Q

what is the standard enthalpy change of formation?

A

it is the energy change when one mole of a substance is formed from its constituent elements in their standard states at 298K and 1 bar

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4
Q

what is the standard enthalpy change of combustion?

A

it is the energy that evolved when one mole of a substance is burnt completely in excess oxygen at 298K and 1 bar.

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5
Q

what is the standard enthalpy change of neutralisation?

A

it is the energy evolved when one mole of water is formed in the reaction between an acid and an alkali at 298K and 1 bar

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6
Q

what is the standard enthalpy change of atomisation?

A

it is the energy absorbed when one mole of gaseous atoms is formed from the element at its standard state at 298K and 1 bar.

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7
Q

what is bond energy?

A

it is the average energy absorbed when one mole of a given covalent bond in a gaseous compound is broken into gaseous atoms

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8
Q

what is lattice energy?

A

it is the energy evolved when one mole of an ionic solid is formed from its constituent gaseous ions

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9
Q

what is the standard enthalpy change of hydration?

A

it is the energy that evolved when one mole of gaseous ions is converted to one mole of aqueous ions at infinite dilution at 298K and 1 bar.

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10
Q

what is the standard enthalpy change of solution?

A

it is the energy change when one mole of a substance is completely dissolved in infinite dilution in an aqueous solution at 298K and 1 bar

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11
Q

what is the first electron affinity?

A

it is the energy change when one mole of gaseous atoms of an element gain one mole of electrons to form one more of singly charged negative gaseous ions.

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12
Q

to determine heat change of a reaction conducted in the calorimeter…

A

we use the equation q = mc(del)T

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13
Q

what are the assumptions applied to determine heat change of a reaction?

A
  1. there is no heat lost to the surroundings
  2. the heat capacity of the solution is approx. to that of water and has a value of 4.18Jg^-1K^-1
  3. the density of the solution is approx. to that of water and has a value of 1gcm^-3
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14
Q

the enthalpy change of a reaction can be determined using…

A

q/n

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15
Q

what is hess’ law?

A

it states that the enthalpy change for a reaction is the same whether the reaction takes place in one step or in a series of steps and is determined by the initial and final states of the system

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16
Q

define entropy

A

it is the measure of the randomness or the disorder in a system

17
Q

what does a positive entropy value mean?

A

the final state is more disordered than its initial state

18
Q

what does a negative entropy value mean?

A

the final state is less disordered than its initial state

19
Q

how does temperature affect entropy?

A

entropy increases when temperature increases as there are more ways of arrangement for the particles and there is a broadening of the energy distribution, leading to more energy states which the particles can adopt.

20
Q

how does the change in the number of particles affect entropy?

A

it increases as there is an increase in the number of ways to arrange the particles.

21
Q

how does mixing the particles increase entropy?

A

there are more ways to arrange the particles after mixing.

22
Q

what is the standard gibbs free energy change equation?

A

change in standard gibbs free energy = standard enthalpy change of the system - temperature*standard entropy change of the system

23
Q

if change in standards gibbs free energy > 0…

A

the chemical reaction is spontaneous

24
Q

if change in standards gibbs free energy < 0…

A

the chemical reaction is NOT spontaneous

25
Q

what are the limitations of the use of “change in standard gibbs free energy”?

A

thermodynamic feasibility does not predict the kinetics of a reaction, such as its rate and the reaction may not take place because of a high activiation energy barrier

26
Q
A

chemistry (7 decks)

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