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Chemistry > Thermodynamics > Flashcards

Thermodynamics Flashcards

1
Q

Hess Law

A

enthalpy change for a chemical reaction is the same regardless the route taken from the reactants to products

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2
Q

standard enthalpy of formation

A

-enthalpy change when 1 mole of a compound is formed
-from its elements under standard conditions
-all reactants and products in their standard states

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3
Q

standard enthalpy of combusion

A

-enthalpy change when 1 mole of compound is completely burned in oxygen
-under standard conditions
-all reactants and products in their standard states

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4
Q

standard enthalpy of atomisation

A

-enthalpy change when 1 mole of gaseous atoms
-formed from element in its standard state

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5
Q

mean bond enthalpy

A
  • enthalpy change when 1 mole of gaseous molecule
    -each break covalent bond to form 2 free radicals
    -averaged over a range of compounds
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6
Q

relationship between bond enthalpy + atomisation

A

atomisation x2 = bond enthalpy

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7
Q

first ionisation enthalpy

A

-enthalpy change when 1 mole of electrons
-removed from 1 mole of gaseous atoms
-to produce 1 mole of gaseous ions
-each which a single positive charge

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8
Q

second ionisation enthalpy

A

-enthalpy change when 1 mole of electrons
-removed from 1 mole of gaseous 1+ ions
-to produce 1 mole of gaseous ions
-each which a 2+ positive charge

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9
Q

first electron affinity

A

-standard enthalpy change when 1 mole of gaseous atoms
-converted into 1 mole of gaseous ions
-each with a single negative charge
-under standard conditions

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10
Q

second electron affinity

A

-standard enthalpy change when 1 mole of electrons is added to
-1 mole of gaseous ions
-each with a single negative charge
-to form 1 mole of gaseous ions with 2- charge

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11
Q

lattice formation enthalpy

A
  • standard enthalpy change when 1 mole of solid ionic compound is formed
    -from its gaseous ions
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12
Q

lattice formation enthalpy

A

-standard enthalpy change when 1 mole of solid ionic compound is formed
-from its gaseous ions

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13
Q

lattice dissociation enthalpy

A

-standard enthalpy when 1 mole of solid ionic compound
-dissociates into its gaseous ions

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14
Q

standard enthalpy of hydration

A

-standard enthalpy change when 1 mole of gaseous ions
-converted into 1 mole of aqueous ions

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15
Q

standard enthalpy of solution

A

-standard enthalpy change when 1 mole of solute dissolves
[-in enough solvent to form a solution
-ions are far apart to not interact with each other]

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16
Q

mean bond enthalpy equation

A

mean bond enthalpy = sum of [reactants]- sum of [products]

17
Q

two factors which determine how exothermic a lattice enthalpy is

A
  • charge on ion [greater the charge, greater its attraction to an oppositely charged ion]
  • size of ion [smaller the ion, greater the attraction to an oppositely charged ion]

top tip:

the more exothermic, the stronger the ionic bonds

18
Q

Covalent character eg. [Zn]2+ and [Se]2-

A

-Zn ion is quite small, strong + charge
-Se ion is quite large, strong - charge
-two form ionic attraction due to electrostatic attraction
-Zn ion is strongly polarising
-Se electron cloud is distorted
-some of the e- density is distorted
-this is covalent character

19
Q

ionic bonding

A

strong electrostatic attraction between oppositely charged ions

20
Q

perfect ionic model and features

A

-purely ionic bonding w no covalent character
-ions act as point charges
-ions are perfect spheres which cannot be distorted

21
Q

what is the effect of covalent character on lattice enthalpy

A
  • more exothermic
    -stronger bonding
22
Q

solid to liquid
inc or dec of entropy

A

increase in entropy

23
Q

what is happening in terms of bonds when dissolving ionic compounds

A
  • breaking ionic bonds
  • form bonds between water molecules + ions
24
Q

mixing 2 liquids
inc or dec of entropy

A

increase in entropy

25
Q

3 factors which determine if a reaction is feasible

A

-temperature
-enthalpy
-entropy

26
Q

entropy key knowledge
-units
-definition
-delta?

A

-it is delta S
-delta S is the change in entropy
-units are JK-1mol-1
-measure of disorder

27
Q

evaporating a liquid
inc or dec of entropy

A

increase in entropy

28
Q

more moles produced
inc or dec of entropy

A

increase in entropy

29
Q

entropy equation

A

change in entropy = sum [products]-sum [reactants]

30
Q

standard conditions for entropy

A

100 KPa
298 K
1 mol dm-3

31
Q

feasible definition [2]

A

-reaction can happen at a given temp
- feasible when delta G is less then or = to 0

32
Q

Gibbs free energy equation

A

*G = H-[TxS}
G= gibbs free energy KJ mol-1
H= enthalpy change KJ mol-1
T= temperature Kelvin
S= entropy change kJK-1mol-1

Chemistry (15 decks)

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