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oceans Flashcards

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1
Q

calculation for entropy change of the system

A

entropy of products - entropy of reactants

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2
Q

calculation for entropy change of the surroundings

A
  • delta H / Temperature (in K)
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3
Q

calculation for total entropy change

A

entropy of system + entropy of surroundings

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4
Q

calculation for working out minimum temperature of reaction (T at which total entropy change = 0)

A

Tmin = delta H / entropy of system

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5
Q

entropy definition

A

the measure of disorder / number of ways of arranging particles

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6
Q

relationship between total entropy change and reaction feasibility

A

if total entropy change is positive, reaction is feasible

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7
Q

lattice enthalpy meaning

A

the enthalpy change when 1 mole of an ionic solid is formed from its gaseous ions

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8
Q

features of change in lattice enthalpy

A
  • always negative (exothermic)
  • more negative = stronger ionic bond
  • more negative with higher ionic charge (stronger attraction) and smaller ionic radius (ions closer together) => higher charge density
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9
Q

change in hydration enthalpy meaning

A

the enthalpy change when an aqueous solution is formed from one mole of gaseous ions

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10
Q

features of change in hydration enthalpy

A
  • always negative (exothermic)
  • more negative = stronger ion-dipole forces
  • more negative with higher ionic charge and smaller ionic radius => higher charge density
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11
Q

enthalpy change of solution meaning

A

the enthalpy change when one mole of a solute is dissolved to infinite dilution

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12
Q

feature of enthalpy change of solution

A

positive or negative

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13
Q

calculating enthalpy change of solution (formula)

A

enthalpy change of solution = enthalpy change of hydration - change in lattice enthalpy

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14
Q

calculating enthalpy change of solution (practical)

A

a. q (J) = mass of solution x shc of water x change in temperature
b. moles of salt = mass / Mr
c. enthalpy change of solution = -q (kJ) / moles of salt

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15
Q

enthalpy change of solution practical process (and method for investigating the dissolving of salts)

A
  1. measure volume of water using a measuring cylinder
  2. use and insulated cup and lid
  3. measure the initial temperature
  4. add solid salt and measure the final temperature when temperature stops changing
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16
Q

greenhouse effect

A

-solar energy reaching earth is UV
- earth absorbs some of this UV, heating up and emitting IR
- greenhouse gases (e.g. CO2 and methane) in troposphere absorb some of this IR in the IR window
- absorption of IR by greenhouse gas molecules increases the vibrational energy o their bands the energy is transferred to other molecules by collisions, thus increasing their kinetic energy and raising temperature
- greenhouse gas molecules also remit some o the absorbed IR in all directions -> some of it heats up the earth
- increased concentrations of greenhouse gases leads to enhanced greenhouse effect

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17
Q

what is the IR window

A

a part of the spectrum where water doesn’t absorb a greenhouse gas

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18
Q

what is Ksp

A

the solubility product

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19
Q

Ksp expression

A

Ksp = [product 1 +] [product 2 -]

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20
Q

precipitation formation and Ksp

A

a precipitate will form when the product of the concentration of ions is greater than Ksp

21
Q

calculation for pKa

A

pKa = -log10 (Ka)

22
Q

calculation for pH

A

pH = -log10 [H+]

23
Q

calculation for [H+] (from pH)

A

[H+] = 10 ^ -pH

24
Q

ph calculation for strong acids

A

[H+] = [acid]
unless [H+] = 2 x [H2SO4]

25
Q

assumption of pH calculation for strong acids

A

assumes complete dissociation into ions

26
Q

pH calculation for weak acids

A

[H+] = square root of (Ka x [acid])

27
Q

calculation for Ka for weak acids

A

Ka = [H+]^2 / [acid]

28
Q

assumptions for pH calculation for weak acids

A
  • [H+] = [A-]
  • [HAeq] = [HAinit]
29
Q

pH calculation for strong alkalis

A

[H+] = Kw / [OH-]

30
Q

assumption for pH calculation of strong alkalis

A

assumes complete dissociation itno ions

31
Q

Ka calculation for buffers

A

Ka = [H+] x [salt]/[acid]

32
Q

[H+] calculation for buffers

A

[H+] = Ka x [acid]/[salt]

33
Q

assumptions for pH calculations for buffers

A
  • [A-] = [salt]
  • [HAeq] = [acid]
34
Q

strong acid definition

A

acid that fully dissociates into ions in a solution

35
Q

how do buffers work when you add an acid

A

HA <==> H+ + A-
increased [H+]
equilibrium shifts to left (H+ reacts with A-)
[H+] and pH are restored
need high concentration of [A-] for H+ to react with

36
Q

how do buffers work when you add an alkali

A

HA <==> H+ + A-
decreased [H+]
equilibrium shifts to the right (HA forms H+ and A-)
[H+] and pH are restored

37
Q

acid definition

A

proton donors

38
Q

base definition

A

proton acceptors

39
Q

relationship between acid strength and Ka/pKa

A

stronger acids have a higher Ka and a lower pKa

40
Q

conjugate acid meaning

A

formed when a proton is added to a base

41
Q

conjugate base meaning

A

formed when a proton is removed from an acid

42
Q

weak acid meaning

A

does not dissociate completely in water
forms some H+ ions but there is still unreacted acid in the solution

43
Q

factors determining the relative solubility of a solute in aqueous and non-aqueous solvents

A
  • when a solute dissolves, the solute and solvent bonds break and new ones are formed
  • usually substances won’t dissolve if the broken bonds are stronger than the new ones
  • solvents can be polar or non-polar
44
Q

ionic substances + dissolving

A

only usually dissolve in polar solvents, creating an aqueous solution
because
- the H atoms in water have a positive partial charge and the O atoms have a partial negative charge
- the ions bond to these dipoles to form ion-dipole bonds
- this causes the ions to leave the ionic lattice, and they become randomly distributed
all lattices which can be pulled apart by the ion-dipole bonds are double

45
Q

covalent substances and dissolving

A

usually intermolecular bonds between covalent substances are weak
similarly, non-polar solvent also have weak id-id bonds because the forces are similar, most covalent substances will dissolve in non-polar solvents
in polar solvents, the H bonds between water molecules are much stronger than the bonds that would form if the substance dissolved so most covalent substances are not soluble in polar solvents

46
Q

hydrated ions definition

A

an ion that is surrounded by its own shell of water molecules

47
Q

factors affecting entropy

A
  • gases have more entropy than l and s, liquids have more entropy than s
  • more complicated molecules have higher entropy
  • mixtures have more entropy than pure liquids
48
Q

strong base definition

A

nearly completely dissociate in water to form OH- ions

chemistry (8 decks)

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