Chemical Equilibrium

Question 1

concentration value of solid or solvent in equlibrium constant equation

Answer 1

1

Question 2

effect of catalyst on equilibrium constant and position

Answer 2

no effect, equilibrium is just reached faster

Question 3

effect of temperature change on equilibrium constant and position

Answer 3

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

Question 4

K

Answer 4

equilibrium constant

Question 5

equilibrium in water and aqueous solutions

Answer 5

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

Question 6

H30+ (aq)

Answer 6

same as H+, hydronium ion

Question 7

Kw

Answer 7

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

Question 8

value of Kw at 25oC

Answer 8

1.0 x 10-14

Question 9

amphoteric and example

Answer 9

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

Question 10

strong acid

Answer 10

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

Question 11

weak acid

Answer 11

partially dissociates in aqueous solution eg. methanoic, carbonic

Question 12

equilibrium postion in weak acid dissociations

Answer 12

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

Question 13

bases

Answer 13

substances that can reaction with H+ to form water

Question 14

strong base

Answer 14

ionic and dissociate completely, ex. metal hydroxides

Question 15

weak base

Answer 15

partially dissociate, ex. ammonia and amines

Question 16

strong base pH and conductivity

Answer 16

high pH (13-14) and conductivity

Question 17

weak base pH and conductivity

Answer 17

low pH (11-12) and conductivity

Question 18

salts of a weak acid and strong base give

Answer 18

alkaline solution

Question 19

salts of strong acid and weak base give

Answer 19

acidic solution

Question 20

salts of strong acid and stong base give

Answer 20

neutral solution

Question 21

stoichemistry

Answer 21

numerical propotions of substances involved in a reaction

Question 22

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

Answer 22

10^-7 mol

Question 23

bronsted- lowry defintion of acids and bases

Answer 23

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

Question 24

proton

Answer 24

H+ ion

Question 25

buffer

Answer 25

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

Question 26

what are buffers made from?

Answer 26

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

Question 27

how does a buffer work if acid is added?

Answer 27

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

Question 28

how does a buffer work if a base is added?

Answer 28

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

Question 29

pH of buffer solution equation

Answer 29

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

Question 30

[ ]

Answer 30

concentration

Question 31

acid indicator dissociation constant equation

Answer 31

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

Question 32

equivalence point

Answer 32

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

Question 33

what are indictors usually made of?

Answer 33

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

Question 34

enthalpy of formation

Answer 34

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

Question 35

standard conditions

Answer 35

298K (25C) and one atmosphere

Question 36

entropy of a system

Answer 36

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

Question 37

entropy when solid reactants change to gaseous products

Answer 37

postive

Question 38

second law of thermodynamics

Answer 38

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

Question 39

entropy of a perfect crystal at 0K

Answer 39

0

Question 40

what is the standard entropy of a substance?

Answer 40

entropy for the standard state of a substance

Question 41

spontaneous reaction

Answer 41

can occur on its own

Question 42

if ΔS>0 is reaction spontaneous?

Answer 42

postive entropy change, reaction is spontaneous

Question 43

if ΔS<0 is reaction spontaneous?

Answer 43

negative entropy change, reaction is not spontaneous

Question 44

ΔG

Answer 44

free energy

Question 45

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

Answer 45

yes, equilibrium composition favours products over reactants

Question 46

equation for change in free energy

Answer 46

ΔG= TΔS

Question 47

entropy units

Answer 47

JK-1

Question 48

equation to find what temperature a reaction becomes feasible

Answer 48

T= ΔH/ΔS

Question 49

rate equation

Answer 49

rate= k[A][B]

Question 50

k

Answer 50

rate constant

Question 51

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

Answer 51

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

Question 52

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

Answer 52

zero order

Question 53

what can order of a reaction only be determined from?

Answer 53

experimental data

Question 54

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

Answer 54

mol l-1 s-1

Question 55

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

Answer 55

s-1

Question 56

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

Answer 56

mol-1 l s-1

Question 57

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

Answer 57

mol-2 l2 s-1

Question 58

rate constant equation

Answer 58

k= rate/[A][B]

Question 59

rate determining step

Answer 59

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