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Chemistry A Level > 1.8 Thermodynamics > Flashcards

1.8 Thermodynamics Flashcards

1
Q

What is the sign for enthalpy change of a solution?

A

🔺Hsol

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2
Q

What is the enthalpy change of solution?

A

The enthalpy change when one mole of an ionic solid is dissolved in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other

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3
Q

What is the sign for hydration enthalpy?

A

🔺Hhyd

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4
Q

What is the hydration enthalpy?

A

The enthalpy change when one mole of gaseous ions become hydrated (ie dissolved in water)

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5
Q

What is the sign for Lattice enthalpy of formation?

A

🔺Hlef

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6
Q

What is the lattice enthalpy of formation?

A

The enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase

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7
Q

What is the sign for the lattice enthalpy of dissociation?

A

🔺Hled

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8
Q

What is the lattice enthalpy of dissociation?

A

The enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase

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9
Q

Describe the equation for the Hess cycle for calculating the enthalpy of a solution

A

(Hydration enthalpies) - (Lattice enthalpy of formation) = Enthalpy change of a solution

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10
Q

What is the sign for Electron Affinity?

A

🔺Hea

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11
Q

What is the Electron affinity?

A

The first electron affinity is the enthalpy change when one mole of gaseous atoms gains one electron per atom to produce gaseous 1- ions.

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12
Q

What is the sign for Enthalpy of atomisation?

A

🔺Hat

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13
Q

What is the enthalpy of atomisation?

A

The enthalpy change when one mole of gaseous atoms is produced from an element in its normal state

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14
Q

What is the sign for Bond dissociation enthalpy?

A

🔺Hdis

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15
Q

What is the bond dissociation enthalpy?

A

The enthalpy change when one mole of covalent bonds is broken in the gaseous state.

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16
Q

What is the enthalpy of bond dissociation?

A

The enthalpy change when one mole of bonds of the same type in gaseous molecules under standard conditions are broken, producing free radicals.

17
Q

What is the correlation between the magnitude of the lattice enthalpy and the strength of the bonding?

A

The greater the lattice enthalpy the stronger the bonding.

18
Q

What is a Born-Haber cycle?

A

A cycle that includes all the enthalpy changes in the formation of an ionic compound.

19
Q

Describe a born-Haber cycle

A

Elements in their standard states undergo atomisation to form gas atoms, then 1st (+2nd etc) ionisation energy to form metal ions, then electron affinity to form gas ions , then lattice enthalpy of formation to form the ionic compound.

20
Q

What is needed when constructing a Born-Haber cycle ?

A
  • Steps should have values and labels written on
  • it’s best to show each separate step
  • sometimes each separate ionisation enthalpy and/or electron affinity are shown as separate steps
21
Q

What factors affect the lattice dissociation enthalpy ?

A
  • The size of the ions
  • The charge on the ions
  • The distance from the centre of one ion to the next.
22
Q

What is entropy?

A

The degree of disorder in a system is called entropy (S)

23
Q

What is the unit for entropy?

A

J/K/mol

24
Q

What is the second law of thermodynamics?

A

In a closed system, entropy will increase

25
Q

What is the 3rd law of Thermodynamics?

A

Entropy is zero at absolute zero (0Kelvin) and increases with temperature

26
Q

Is there a bigger entropy change in melting or boiling?

A

In boiling

27
Q

The more ordered a structure the higher or lower the entropy?

A

The lower the entropy

28
Q

How do you calculate the standard entropy change ?

A

🔺S = sum of entropy of products - sum of entropy of reactants

29
Q

What is the Gibbs free energy change?

A

Used to calculate the total entropy change for a system and it’s surroundings and shows the feasibility (likelihood) of a process to occur spontaneously.

30
Q

What is the equation to calculate the Gibbs free energy change ?

A

🔺G = 🔺H -T🔺S
🔺H - Enthalpy change
-T🔺S - temperature (K) x total entropy change

31
Q

What must the Gibbs free energy change be for a reaction to be feasible?

A

Negative or below zero

32
Q

What does it mean if the Gibbs free energy change is equal to zero?

A

The system is in equilibrium

33
Q

What is the unit for Gibbs free energy change?

A

KJmol-1

34
Q

What equation be used to calculate the entropy change when a substance is changing state

A

🔺S= 🔺H / T

35
Q

What is the gradient in a Gibbs free energy graph equal to?

A

Gradient =-🔺S

Chemistry A Level (35 decks)

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