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GAMSAT Chemistry (General) > 4. Chemical Reactivity > Flashcards

4. Chemical Reactivity Flashcards

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1
Q

what does pressure favor for equilibrium

A

Favours form of fewer moles of gas

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2
Q

what is the equilibrium constant

A

conc of reactant and product at equilibrium

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3
Q

what is the unit for equilibrium constant

A

molL-1

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4
Q

what does a large kc >10^5 mean

A

completely convert reactant to product

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5
Q

what does a very small kc <10^-5 mean

A

very small number of reactants turn into products

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6
Q

what is the unit for solubility

A

gL-1

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7
Q

what is the reaction quotient

A

determines direction reaction shifts to reach equilibrium

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8
Q

what does it mean if Q<K for the reaction quotient

A

forwards/to the right

reactant to product

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9
Q

what does it mean if Q>K for the reaction quotient

A

reverse/to left

products to reactants

precipitation

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10
Q

what does it mean if Q=K for the reaction quotient

A

reaction is already at equilibrium

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11
Q

what is Q regarding the reaciton quotient

A

ionic product

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12
Q

what does increased conc of the ion or common ion effect do to the reaction in terms of direction itll proceed and solubility

A

drives reverse reaction

decrease solubility

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13
Q

what is the common ion effect

A

add reagent with which cations form soluble complex

eg Ag+ + 2NH3 -> [Ag(NH3)2]+

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14
Q

what is the colour of phenolphthalein in acid and base

A

acid = colourless
base = pink

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15
Q

what is the colour of bromothymol blue in acid and base

A

acid = yellow
base = blue

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16
Q

what does acids do in terms of protons

A

transfer/donate H+ to others

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17
Q

what does bases do in terms of protons

A

accept H+ from others

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18
Q

increase conjugate acid strength does what to the base strength

A

decreases conjugate base strength and vice versa

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19
Q

what is ka’s relationship with acid strength

A

increased ka = stronger acid

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20
Q

what is ka’s relationship with pka

A

increase ka = decrease pka

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21
Q

what is pka’s relationship with acid strength

A

small pka = stronger acid

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22
Q

what is the equation relating pka and ka

A

pka = -log10ka

ka = 10^-pka

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23
Q

if the buffer is equimolar then what is the relationship of the pH of the buffer and the pka of acid

A

pH buffer = pka acid

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24
Q

for a titration of weak acid/base and added strong acid/base how do you calculate the pH of the original acid

A

added volume of strong base/acid = 0 at this point

  1. write reaction equation for the weak acid/base
  2. write ka expression
  3. solve for [H3O+]
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25
Q

for a titration of weak acid/base and added strong acid/base how do you calculate the volume of added acid/base at equivalence

A

equivalence point = n(acid) = n(base)

  1. find n(weak acid/base)
  2. mole ratio of weak acid/base and added volume
  3. find n(added volume) from ratio mole
  4. find volume thats added via C=n/V
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26
Q

for a titration of weak acid/base and added strong acid/base how do you calculate the volume of added acid/base when pH = pka

A

pka = pH when v(added volume) = 1/2 amount of weak acid/base

v(added) = v(equivalence)/2

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27
Q

for a titration of weak acid/base and added strong acid/base how do you calculate pH

A
  1. write equation for reaction between weak acid/base with added strong acid/base
  2. identify ka or kb expression
  3. find [ion react with H2O] via C=n/V
  4. solve ka or kb for [H3O+]
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28
Q

for a titration of weak acid/base and added strong acid/base how do you calculate the pH after x amount of added volume is added

A

after equivalence will have extra of added volume

  1. new conc = original conc x (extra volume/total volume)
  2. find [H+] to find pH
29
Q

what is the buffer zone

A

where buffer is effective over pH range of pka +/- 1

30
Q

for a zero order reaction what is the change in rate when there is a change in [A]

what equation represents this - rate is proportional to.. and rate = …

A

no change in change in rate

rate proportional to [A]^0
rate = k

31
Q

for a first order reaction what is the change in rate when there is a change in [A]

what equation represents this - rate is proportional to.. and rate = …

A

rate x2 when [A] x 2

rate proportional to [A]^1
rate = k[A[

32
Q

for a second order reaction what is the change in rate when there is a change in [A]

what equation represents this - rate is proportional to.. and rate = …

A

4 x rate when [A] x 2

rate proportional to [A]^2
rate = k[A]^2

33
Q

for a zero order reaction what is the unit of k

A

molL^-1s^-1

34
Q

for a first order reaction what is the unit of k

A

s^-1

35
Q

for a second order reaction what is the unit of k

A

Lmol^-1s^-1

36
Q

for a third order reaction what is the unit of k

A

L^2mol^-2s^-1

37
Q

what is the [R] rate law equation for first order reaction

A

[R] = [Ro]e^(-kt)

ln[R] = ln[Ro] - kt

38
Q

for a first order reaction what is the plot of ln[R] vs time like

A

linear

39
Q

what are the 2 possible combinations of 2nd order reaction

A

single reactant in 2nd order

or

2 reactants in first order

40
Q

what assumption is made for a second order reaction that is made up of 2 1st order reactions

A

that one of the reactants’s conc is very large

41
Q

what is the rate law equation for second order reaction and a pseudo first order

A

1/[R] = 1/[Ro] + kt

k1 = [R]
pseudo first order

42
Q

what is the half life rate equation for zero order reactions

A

[R] = [Ro] - kt

t1/2 = [Ro]/2k

43
Q

what is the half life rate equation for first order reactions

A

ln[R] = ln[Ro] - kt

t1/2 = ln2/k

44
Q

what is the half life rate equation for second order reactions

A

1/[R] = 1/[Ro] + kt

t1/2 = 1/[Ro]k

45
Q

what is the half life

A

time for conc of reactant to fall to 1/2 its original value

46
Q

what are the 2 conditions for a effective collision

A

molecule has high enough energy to overcome activation energy

correctly aligned molecules

47
Q

what is the relative energy of the multistep reactivity when it comes to reactive intermediates

A

minimum energy

48
Q

what is the relative energy of the multistep reactivity when it comes to transition states

A

max energy

49
Q

when do catalysts act in the reaction pathway

A

usually early step and regenerates in later step

50
Q

what are homogenous catalysts

A

catalysts working in same phase as reaction

51
Q

what are heterogenous catalysts

A

catalysts working in different phase from reaction

52
Q

what do catalysts do - 2 possible actions

A

provides different path of lower Ea = faster reaction rate

or

molecules are aligned by the catalyst

53
Q

what is the rate determining step

A

the slowest step

54
Q

what are bronstead acids

A

proton H+ can be taken by base

55
Q

what are bronstead bases

A

take proton H+ from acid

56
Q

what are amphoteric substances

A

can act as both acid or base

57
Q

what does a -pH mean

A

pH is + for [H+] <1molL^-1

-pH means very acidic

58
Q

what are the bonds like in strong acids

what does this mean for the distance between atoms and the e- density

A

short bonds so atoms are closer together

e- density between 2 atoms is large

59
Q

decrease in e- density of bond means what for the strength of the bond

A

decrease strength of bond

60
Q

what are the 2 ways that the e- density in bond regarding acidity of substance be affected

A

decrease amount of charge

charge stabilization

61
Q

why does decreasing the amount of charge affect the e- density in bond regarding acidity of substance

A

easier for + molecule to lose + H+ ion so if acid loses H+ then the conj base is 1 unit charge more negative

62
Q

what are the 2 ways that charge stabilization affect the e- density in bond regarding acidity of substance

A
  1. inductive effects
  2. delocalisation
63
Q

for charge stabilization affecting the e- density in bond regarding acidity of substance - explain the inductive effects

A

presence of nearby electronegative atom/e- withdrawing groups move charge away from acidic H = weaker H bond

64
Q

for charge stabilization affecting the e- density in bond regarding acidity of substance - explain the delocalisation effects

A

spread charge over larger number of atoms - occurs via resonance

65
Q

regarding speciation

if pH < pka what does this mean for the acid and base forms

A

have higher acid forms (HA) than base form proportionally

66
Q

regarding speciation

if pH > pka what does this mean for the acid and base forms

A

have higher base forms (A-) than acid form proportionally

67
Q

how do you calculate the pH of an amphoteric substance solution

A

pH = 1/2(pka1 + pka2)

68
Q

buffers work best in what range

A

at pH = pka +/- 1

GAMSAT Chemistry (General) (4 decks)

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