chemistry chapter 1 - rate of reaction

Chapter 1 : Rate of Reaction

1.1 Rate of Reaction 1. Chemical reaction = _________ mixed together under __________________

A + B C + D

Graph of amount of substance (mol) against time (minutes)

2. Rate of reaction = _________ of a chemical reaction

3. Methods of measuring reaction rates Mass of substance Concentration of substance Volume of gas produced per unit of time Changes in colour Formation of precipitates

4. The rate of reaction can be expressed in the average rate of reaction over a period of time, or the rate of reaction at any given time


1.2 Factors that Affect the Rate of Reaction (1) Surface area (particle size) of the solid reactant

Mg (ribbon/powder) (s) + H2SO4 (aq) MgSO4 (aq) + H2 (g) Smaller size > larger TSA > higher RoR

(2) Concentration of reactant Mg (s) + 2HCl (diff conc.) (aq) MgCl2 (aq) + H2 (g) Higher conc. > higher RoR

(3) Temperature Zn (s) + H2SO4 (diff temp.) (aq) ZnSO4 (aq) + H2 (g) Higher temp. > higher RoR

(4) Pressure (only for reactions that involve gases) N2 (g) + 3H2 (g) ⇄ NH3 (g) ------ Haber process Higher pressure > higher RoR

(5) Presence of catalysts Catalyst = Substance that changes the __________________ but is

itself chemically Press/ure (for reactions involving gases) Positive catalyst : ( ) RoR ; Negative catalyst ( ) RoR 2H2O2 (aq) 2H2O (l) + O2 (g)

With catalyst, reaction that occurs slowly > vigorous effervescence Characteristics of catalysts

*_________ amount is required*highly _________*changes RoR ; does not change _________ of chemical reaction*remain chemically _________ after the reaction*physical appearance may change*with poison, effectiveness decreased*with promoter, increase reactivity and effectiveness*some catalysts can catalyse several chemical reactions


1.2.2 Applications of factors that affect rates of reaction1. Combustion of charcoal

Combustion of charcoal = reaction of charcoal in excess oxygen to produce carbon dioxide andn water

Heat energy is released during combustion >> Large pieces, _______ TSA, _______ RoR, charcoal will not burn easily Small pieces, _______ TSA exposed to air, RoR with oxygen _______

2. Storing food in refrigerators Decomposition (decaying) of food = action of microorganisms Room temp. = optimum temp for breeding of microorganisms Food turns bad quickly at room temp. At low temp, activities of bacteria are slowed down.

Food lasts longer, slow down rate of decaying reaction.

3. Cooking food in pressure cookers Pressure cooker speeds up cooking Higher pressure > water / oil boils at temp. higher than normal b.p.

4. Uses of catalysts in industry Speed up RoR, same amount of products can be obtained in shorter time Lower cost of production Use small pellets of solid catalyst > larger TSA for catalytic reaction Haber process : ammonia Contact process : sulphuric acid Ostwald process: nitric acid


1.3 The Collision Theory 1. Kinetic theory of matter

All matter is made up of _________ , _________ particles Particles are continually moving, have _______________

2. Collision theory

For a chemical reaction to occur, the reacting particles must:*_________ with each other so that the breaking and formation of chemical bonds can occur*possess energy that is equal to, or more than the minimum energy (__________________)*collide in __________________

__________________ : collisions that are successful in producing a chemical reaction (particles react to form new products)

__________________ : collisions that are unsuccessful in producing a chemical reaction (particles collide but bounced back without any changes)


3. Activation energy

Ea : __________________ΔH : __________________

__________________: minimum energy that the reactant particles must possess during collisions for a chemical reaction to occur*can be considered as __________________ that must be overcome by the colliding particles to form product molecules

__________________ : reaction that absorbs heat__________________ : reaction that releases heat

4. Correct orientation


Relating the frequenct of effective collisions with factors influencing the R.o.R

Collision theory two important factors that determine the RoR :

- Frequency of effective collisions- Magnitude of activation energy

(1) Surface area Smaller particle size = greater TSA exposed for reaction to occur Frequency of collision > frequency of effective collision > RoR

(2) Concentration Higher concentration = higher no. of particles per unit volume Frequency of collision > frequency of effective collision > RoR

(3) Temperature Increase temp. > particles absorb heat energy > Kinetic energy of particles increase, thus *reacting particles move faster

*the no. of reacting particles with the activation energy required for the reaction increases

Frequency of collision > frequency of effective collision > RoR Approximately, RoR doubles when temp. increases by 10 oC

(4) Pressure High pressure = smaller volume of gas Gaseous molecules are packed closer >

higher no. of gaseous molecus per unit volume Frequency of collision > frequency of effective collision > RoR


(5) Catalyst Chemical reaction = reactant particles collide with one another With catalyst, reactant particles collide with catalyst and also with each

other Ea can be increased or decreased based on type of catalyst used Thus, catalyst provide an ___________________________ for the

reaction to occur Positive catalyst provide alternative route with _________ activation

energy Thus, more reacting particles possess __________________ required for

the reactionMore reacting particles can overcome the lower Ea required for effective collisions

Ea > frequency of effective collision > RoR

1.4 Practicing Scientific Knowledge to Enhance Quality of Life

1. Air bag – nitrogen gas is released rapidly to expand the air bag2. Machines – speed up or slow down (microwave ovens & refrigerators)3. Oxygen tents – high conc. Of oxygen helps patients to breathe normally4. Enzymes (biological catalysts) – catalyse complex biochemical reactions5. Overcome pollutions, food shortages, diseases

chemistry chapter 1 - rate of reaction

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