Chemical Equilibrium Flashcards

1
Q

concentration value of solid or solvent in equlibrium constant equation

A

1

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2
Q

effect of catalyst on equilibrium constant and position

A

no effect, equilibrium is just reached faster

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3
Q

effect of temperature change on equilibrium constant and position

A

if temp increased, endo reaction favoured
if temp decreased, exo reaction favoured
(if moved to left, K will decrease)

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4
Q

K

A

equilibrium constant

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5
Q

equilibrium in water and aqueous solutions

A

equilibrium between water molecules and hydrogen and hydroxide molecules
H2O(l) + H2O(l) H3O+(aq) + OH-(aq)

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6
Q

H30+ (aq)

A

same as H+, hydronium ion

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7
Q

Kw

A

dissociation constant of water, value of ionic product varies with temp

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8
Q

value of Kw at 25oC

A

1.0 x 10-14

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9
Q

amphoteric and example

A

can act as an acid and a base, depending on environment, ex. water, aluminium oxide

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10
Q

strong acid

A

completely dissociates in aqueous solution, regardless of concentration eg. nitric, hydrochloric

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11
Q

weak acid

A

partially dissociates in aqueous solution eg. methanoic, carbonic

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12
Q

equilibrium postion in weak acid dissociations

A

well to the left, very little H+ ions in acid solution

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13
Q

bases

A

substances that can reaction with H+ to form water

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14
Q

strong base

A

ionic and dissociate completely, ex. metal hydroxides

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15
Q

weak base

A

partially dissociate, ex. ammonia and amines

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16
Q

strong base pH and conductivity

A

high pH (13-14) and conductivity

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17
Q

weak base pH and conductivity

A

low pH (11-12) and conductivity

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18
Q

salts of a weak acid and strong base give

A

alkaline solution

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19
Q

salts of strong acid and weak base give

A

acidic solution

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20
Q

salts of strong acid and stong base give

A

neutral solution

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21
Q

stoichemistry

A

numerical propotions of substances involved in a reaction

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22
Q

concentrations of H+ and OH- in water at 25C

A

10^-7 mol

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23
Q

bronsted- lowry defintion of acids and bases

A

acids= proton donators
bases= proton acceptors
conjugate base and acid= formed by acceptance and donation of protons

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24
Q

proton

A

H+ ion

25
Q

buffer

A

solution in which pH stays approximately constant when small amounts of acid or base are added

26
Q

what are buffers made from?

A

weak acid and one of its salts or weak base and one of its salts

27
Q

how does a buffer work if acid is added?

A

introduced ions combine with A- ions from salt to form HA, H+ ions are mopped up so no fall in pH

28
Q

how does a buffer work if a base is added?

A

OH- and H+ react to form water but equlibium shifts to regenerate more H+ ions so no fall in pH

29
Q

pH of buffer solution equation

A

pH= pKa - log [acid]/[salt]

30
Q

[ ]

A

concentration

31
Q

acid indicator dissociation constant equation

A

Kin= [H+][In]/[HIn]

32
Q

equivalence point

A

theoretical point at which colour change occurs, H+= KIn

33
Q

what are indictors usually made of?

A

weak acids which the colour of the base is different to the colour of it’s conjugate base

34
Q

enthalpy of formation

A

enthalpy change when one mole of a substance is formed from elements in standard states

35
Q

standard conditions

A

298K (25C) and one atmosphere

36
Q

entropy of a system

A

measure of disorder of system, greater disorder= greater entropy, change in state involves changes in entropy

37
Q

entropy when solid reactants change to gaseous products

A

postive

38
Q

second law of thermodynamics

A

total entropy of a reaction system and its surroundings always increase for a spontaneous reaction, heat energy released by reaction system increase entropy of surroundings and heat energy absorbed decreases entropy of surroundings

39
Q

entropy of a perfect crystal at 0K

A

0

40
Q

what is the standard entropy of a substance?

A

entropy for the standard state of a substance

41
Q

spontaneous reaction

A

can occur on its own

42
Q

if ΔS>0 is reaction spontaneous?

A

postive entropy change, reaction is spontaneous

43
Q

if ΔS<0 is reaction spontaneous?

A

negative entropy change, reaction is not spontaneous

44
Q

ΔG

A

free energy

45
Q

if there is a negative change in ΔG, is the reaction spontaneous?

A

yes, equilibrium composition favours products over reactants

46
Q

equation for change in free energy

A

ΔG= TΔS

47
Q

entropy units

A

JK-1

48
Q

equation to find what temperature a reaction becomes feasible

A

T= ΔH/ΔS

49
Q

rate equation

A

rate= k[A][B]

50
Q

k

A

rate constant

51
Q

if rate doubles when [A} doubles and quadruples when [B] doubles…

A

reaction is first order with regards to A anf second order with regards to B

52
Q

if doubling [A] doesnt affect rate of reaction what order is it?

A

zero order

53
Q

what can order of a reaction only be determined from?

A

experimental data

54
Q

if overall order is 0 what are the units for k?

A

mol l-1 s-1

55
Q

if overall order is 1 what are the units for k?

A

s-1

56
Q

if overall order is 2 what are the units for k?

A

mol-1 l s-1

57
Q

if overall order is 3 what are the units for k?

A

mol-2 l2 s-1

58
Q

rate constant equation

A

k= rate/[A][B]

59
Q

rate determining step

A

slowest step in reaction mechanism which the rate of reaction is dependant on