C8 - Rate of Reaction + Reversible reactions

Question 1

rate of reaction

Answer 1

-how fast reactant turn into products

Question 2

Work out rate of reaction

Answer 2

-measure reactants being used up
-products formed

Question 3

Method to measure rate of reaction

Answer 3

-measure starting mass + record as it decreases as gas is lost
-measure increasing gas volume (product) in gas syringe
-measure decreasing light passing through solution = precipitate appears (product)

Question 4

mean rate of reaction

Answer 4

quantity of reactant used/time or quantity of product formed/time

Question 5

Tangent in reaction graphs

Answer 5

-gradient = rate of reaction
-steeper gradient = fast reaction

Question 6

Factors that affect rate

Answer 6

-temp
-SA
-concentration of solution
-pressure of gas
-catalysts

Question 7

collision theory

Answer 7

-when particles of reactants come together
-must collide with enough energy to react

Question 8

activation energy

Answer 8

-minimum energy necessary for particles to react with

Question 9

How to increase rate in terms of particles

Answer 9

-increase frequency of collisions
-increase energy of collisions

Question 10

Increased SA in rate of reaction

Answer 10

-more substance exposed to surface
-faster reaction
-increases frequency of collisions between particles

Question 11

Effect of temp on rate of reaction

Answer 11

-particles have more energy
-for more collisions
-more chances to react
-increases rate and reduces time

Question 12

Increased proportion of particles with more activation energy is

Answer 12

greater effect on rate than increased frequency of collisions

Question 13

Effect of concentration on rate of reaction

Answer 13

-increasing = faster reaction
-more particles moving in same volume
=more collisions

Question 14

Effect on increasing pressure on rate of reaction

Answer 14

-more collisions
-less space for particles to move
-increases rate

Question 15

catalyst

Answer 15

a substance
-increases rate of reaction
-remains chemically unchanged
-does not get used up

Question 16

Eg of catalysts

Answer 16

-iron to make ammonia
-platinum to make nitric acid

Question 17

physical state of catalysts and why

Answer 17

-powder form
-better SA:V
-more effective

Question 18

How do catalysts work

Answer 18

-provide an alternate reaction pathway to product
-lower activation energy is needed
-higher proportion of reactant particles have sufficient energy to react

Question 19

Catalysts effect on frequency of collisions

Answer 19

-increases
-increases rate

Question 20

Pros of catalysts

Answer 20

-cheaper than using extremely high temp/pressure
-save money
-help environment as no burning of fossil fuels
-sustainable = only a little is used

Question 21

poisoned catalysts

Answer 21

-in chemical plants
-contaminated
-is prevented from working

Question 22

reversible reaction

Answer 22

products can react to form reactants again

Question 23

Litmus paper

Answer 23

-complex molecule
-Hlit

Question 24

HLit

Answer 24

-H is for Hydrogen
-red
-add alkali = blue

Question 25

HLit add an alkali

Answer 25

Lit- ion as H is lost

Question 26

HLit can form

Answer 26

H+ and Lit -

Question 27

water of crystallisation

Answer 27

-water contained within a crystal lattice

Question 28

hydrated salt

Answer 28

-salt that contains water of crystallisation

Question 29

anhydrous salt

Answer 29

-doesn't contain water of crystallisation

Question 30

Heating ammonium chloride

Answer 30

-thermal decomp -forms ammonia gas and H

Question 31

Reversible reaction of ammonium chloride

Answer 31

-when heated -2 hot gases rise in test tube -as they cool near top, they react -gases re-form ammonium chloride

Question 32

Energy in reversible reactions

Answer 32

-if a reaction is exothermic -reversed reaction is endothermic -will take in same amount of energy -law of conservation of energy = not destroyed/created

Question 33

stages of reversible reaction - stage 1

Answer 33

-reactants only at start of reaction

Question 34

stages of reversible reaction - stage 2

Answer 34

-rate of forward reaction is greater than reverse reaction

Question 35

stages of reversible reaction - stage 3

Answer 35

-rate of reverse increases as products build up -rate of forward reaction decreases as reactants are used up

Question 36

stages of reversible reaction - stage 4

Answer 36

rates even out -they are the same

Question 37

as concentration of products builds up..

Answer 37

rate of reverse reaction increases -reactants re form -forward reaction decreases

Question 38

equilibrium

Answer 38

reactants make products at the same rate as products make reactants -forward = backward -no change in amount of products and reactants

Question 39

dynamic equilibrium

Answer 39

-forward + reverse reactions continuously take place

Question 40

Le chatelier's principle

Answer 40

-lower concentration of reactants = decreases forward reaction -changing conditions in a system of equilibrium will shift position of equilibrium to cancel out change

Question 41

conditions in Le chatelier's principle consist of

Answer 41

-pressure -temp -concentration

Question 42

Why is Le chatelier's principle important in industry

Answer 42

-chemists must find condition that produces most products in shortest amount of time

Question 43

if the forward reactions produces more gas molecules ..

Answer 43

-increase in pressure decreases products formed -decrease in pressure increases products

Question 44

if forward reaction produces fewer gas molecules..

Answer 44

-increase in pressure increases products -decrease in pressure decreases products

Question 45

when there are equal numbers of molecules of gas on both sides of equation ..

Answer 45

-pressure cannot affect composition of equilibrium mixture -but will speed up reaction in equal amounts

Question 46

change in temp in a closed system

Answer 46

-more products -less reactants

Question 47

if forward reaction is exothermic

Answer 47

-increase in temp decreases products -decrease in temp increases products

Question 48

if forward reaction is endothermic

Answer 48

-increase in temp increases products -decrease in temp decreases products

Question 49

affect of increase in temp on equilibrium

Answer 49

-it shifts to reduce the temp

Question 50

increasing temp favours which reaction

Answer 50

endothermic

Question 51

decreasing temp favours which reaction

Answer 51

exothermic