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chem > energetics > Flashcards

energetics Flashcards

1
Q

what is the standard enthalpy change of reaction?

A

the enthalpy change when molar quantities of reactants as specified by the chemical equation react to form products at 298K and 1 bar

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2
Q

what is the standard enthalpy change of formation?

A

the enthalpy change when 1 mole of substance is formed from its constituent gaseous elements at 298K and 1 bar

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3
Q

what is the standard enthalpy change of combustion?

A

the heat evolved when one mole of a substance is completely burned in excess oxygen at 298K and 1 bar

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4
Q

what is the standard enthalpy change of atomisation of an element?

A

the energy required when one mole of gaseous atoms is formed from the element at 298K and 1 bar

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5
Q

what is the standard enthalpy change of atomisation for a compound?

A

the energy required to convert 1 mole of the compound into gaseous atoms at 298K and 1 bar

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6
Q

what is the standard enthalpy change of neutralisation?

A

the enthalpy change when 1 mole of water is formed in a neutralisation reaction between an acid and a base at 298K and 1 bar

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7
Q

what is lattice energy?

A

it is the heat evolved when 1 mole of ionic solid is formed from its constituent gaseous ions

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8
Q

what is bond energy?

A

the energy required to break 1 mole of a covalent bond in the gaseous state

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9
Q

what is the formula for the weighted average initial temperature?

A

[(temp of x)(vol of x) + (temp of y)(vol of y)]/(total v)

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10
Q

what is the formula to determine heat change of a reaction?

A

q=mcT

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11
Q

what is the formula to determine enthalpy change?

A

enthalpy change = q/n

if exothermic, add a (-) at the front

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12
Q

what is the method to find lattice energy?

A

borne haber cycle

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13
Q

what is required for a borne haber cycle? (if finding lattice energy)

A
  1. enthalpy change of formation of ionic solid
  2. enthalpy change of atomisation of constituent atoms
  3. bond energy for non metal - take note of coefficients
  4. ionisation energy for metal (depending on number of electrons lost)
  5. electron affinity of non metal (first is negative, subsequent all positive)
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14
Q

what is first electron affinity?

A

the enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of singly charged gaseous anions

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15
Q

what is first ionisation energy?

A

the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of singly charged gaseous cations

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16
Q

what is the standard enthalpy change of hydration?

A

the enthalpy change when 1 mole of free gaseous ions is completely dissolved in an infinite volume of water at 298K and 1 bar

17
Q

what is the enthalpy change of solution?

A

the enthalpy change when 1 mole of solute is completely dissolved in an infinite volume of solvent at 298K and 1 bar

18
Q

what is entropy?

A

a measure of randomness or disorder in a system, reflected in the number of ways that particle and their energy can be distributed - greater disorder/ randomness, greater entropy

19
Q

how can we predict change in entropy?

A
  1. change in temperature - temp increase, k.e. increase, more ways to disperse the particles and their energy, entropy increase
  2. change in phase - solid to liquid: particles move more freely in the liquid state, more ways to distribute particles and their energy, entropy increase
  3. change in no. of particles - no. of gaseous particles increase, no. of ways particles and their energy can be distributed increase, entropy increase
  4. mixing of particles - particles mixed, volume allowed to occupy increase, no. of ways particles and their energy can be distributed increase, entropy increase (essentially, volume increase, entropy increase)
20
Q

what is a spontaneous process?

A

it is a process that takes place naturally in the direction stated

21
Q

what is gibbs free energy change of reaction?

A

ΔG = ΔH - TΔS

22
Q

what does the value of ΔG imply?

A

ΔG<0: reaction is spontaneous (exergonic)
ΔG>0: reaction is not spontaneous (endergonic)
ΔG=0: reaction is in equilibrium

chem (5 decks)

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