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a level chem > chapter 22 > Flashcards

chapter 22 Flashcards

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1
Q

what is lattice enthalpy?

A

enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions
under SC

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2
Q

what is enthalpy change of formation?

A

enthalpy change that occurs when one mole of a compound is formed from its elements in their standard states

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3
Q

what is enthalpy change of atomisation?

A

enthalpy change that occurs when one mole of gaseous atoms is formed from the element in its standard state
(always endothermic)

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4
Q

what is first ionisation enthalpy?

A

the enthalpy change required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

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5
Q

what is first electron affinity?

A

enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions

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6
Q

what is enthalpy change of solution?

A

enthalpy change that occurs when one mole of a solute dissolves completely in a solvent

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7
Q

how can you determine enthalpy change of solution experimentally?

A

q = mc^T using mass of solution (with thermometer in)
n using starting mass before added
then q/n

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8
Q

what happens when you dissolve ionic compounds?

A

water molecules are able to break up giant ionic lattice structure and overcome strong electrostatic attractions between opposite charged ions
new bonds form between ions and water molecules

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9
Q

what is enthalpy change of hydration?

A

enthalpy change that accompanies the dissolving of gaseous ions to form one mole of aqueous ions

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10
Q

what is lattice enthalpy a measure of?

A

strength of ionic bonding in a giant ionic lattice

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11
Q

what is the effect of ionic size on lattice enthalpy?

A

increase in ionic radius
attraction between oppositely charged ions decreases
lattice enthalpy becomes less exothermic/negative

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12
Q

what is the effect of ionic charge on lattice enthalpy?

A

increase in ionic charge
attraction between oppositely charged ions increases
lattice enthalpy becomes more exothermic/negative

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13
Q

what can the magnitude of lattice enthalpy show?

A

good indication of melting point of ionic compound
very exothermic lattice enthalpy usually means high melting point

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14
Q

how does ionic radius effect enthalpy change of hydration?

A

ionic radius increases
attraction between ion and water molecules decreases
hydration enthalpy becomes less exothermic/negative

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15
Q

how does ionic charge effect enthalpy change of hydration?

A

ionic charge increases
attraction between ion and water molecules increases
hydration enthalpy becomes more exothermic/negative

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16
Q

what happens to compound the more exothermic it is?

A

the less likely it is to dissolve

17
Q

how can you predict solubility using an equation?

A

enthalpy change of solution = - lattice enthalpy + ∑ enthalpy change of hydration

18
Q

what is entropy?

A

measure of the dispersal of energy and disorder within the chemicals making up the chemical system
symbol = S
units = JK-1mol-1

19
Q

what are systems like that have high entropy?

A

more chaotic systems

20
Q

what happens when entropy increases?

A

energy is spread out more

21
Q

what does the production of gas cause in a equation?

A

increases disorder of particles
energy is more spread out
increases entropy
S is positive

22
Q

what happens if moles in a equation decrease from reactants to products?

A

decrease in randomness of particles
energy is less spread out
decreases entropy
S is negative

23
Q

what is standard entropy?

A

entropy of one mole of a substance under standard conditons

24
Q

what is standard entropy equation?

A

∑standard entropy of products - ∑standard entropy of reactants

25
Q

what is free energy (^G)?

A

overall change in energy during a chemical reaction/process

26
Q

how do you calculate free energy (^G)?

A

enthalpy change - (T x standard entropy)
^G = ^H - T^S

27
Q

when is a reaction energetically feasible?

A

if ^G is negative

28
Q

when is a reaction always feasible?

A

when ^H is negative and ^S is positive

29
Q

when is a reaction never feasible?

A

when ^H is positive and ^S is negative

30
Q

what is the point at which a reaction becomes feasible?

A

^G = 0

31
Q

why can some reactions have a negative ^G value but not take place so are not feasible?

A

activation energy is very high so reaction is very slow so seems to not be happening at all

a level chem (22 decks)

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