chemistry > oceans > Flashcards

oceans Flashcards

(48 cards)

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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

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A

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

21
Q

calculation for pKa

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A

pKa = -log10 (Ka)

22
Q

calculation for pH

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A

pH = -log10 [H+]

23
Q

calculation for [H+] (from pH)

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A

[H+] = 10 ^ -pH

24
Q

ph calculation for strong acids

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A

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

25
assumption of pH calculation for strong acids
assumes complete dissociation into ions
26
pH calculation for weak acids
[H+] = square root of (Ka x [acid])
27
calculation for Ka for weak acids
Ka = [H+]^2 / [acid]
28
assumptions for pH calculation for weak acids
- [H+] = [A-] - [HAeq] = [HAinit]
29
pH calculation for strong alkalis
[H+] = Kw / [OH-]
30
assumption for pH calculation of strong alkalis
assumes complete dissociation itno ions
31
Ka calculation for buffers
Ka = [H+] x [salt]/[acid]
32
[H+] calculation for buffers
[H+] = Ka x [acid]/[salt]
33
assumptions for pH calculations for buffers
- [A-] = [salt] - [HAeq] = [acid]
34
strong acid definition
acid that fully dissociates into ions in a solution
35
how do buffers work when you add an acid
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
how do buffers work when you add an alkali
HA <==> H+ + A- decreased [H+] equilibrium shifts to the right (HA forms H+ and A-) [H+] and pH are restored
37
acid definition
proton donors
38
base definition
proton acceptors
39
relationship between acid strength and Ka/pKa
stronger acids have a higher Ka and a lower pKa
40
conjugate acid meaning
formed when a proton is added to a base
41
conjugate base meaning
formed when a proton is removed from an acid
42
weak acid meaning
does not dissociate completely in water forms some H+ ions but there is still unreacted acid in the solution
43
factors determining the relative solubility of a solute in aqueous and non-aqueous solvents
- 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
ionic substances + dissolving
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
covalent substances and dissolving
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
hydrated ions definition
an ion that is surrounded by its own shell of water molecules
47
factors affecting entropy
- 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
strong base definition
nearly completely dissociate in water to form OH- ions
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