The document discusses the rate of reaction and factors that affect it. It defines rate of reaction as the observable change in quantity of a reactant or product over time. Examples are given of fast reactions, such as burning of sodium and reaction of metals with water or acids. Slow reactions include precipitation of sulfur and rusting of iron. Factors like concentration, temperature, catalysts and surface area influence the rate.

1. RATE OF REACTION
CHAPTER 1

2. In this chapter, you will learn to:
Analyse the rate of reaction.
Synthesise factors affecting the rate of reaction.
Synthesise ideas on the collison theory
Learn about practising scientific knowledge to enhance quality
of life.

3. 1.1 ANALYSING RATE OF
REACTION

4. LEARNING OUTCOMES
State what rate of reaction is.
Identify observable changes to reactants or products for
determining rate of reaction.
Determine average rate of reaction.
Determine the rate of reaction at any given time from a graph.
Solve numerical problems involving average rate of reaction.
Solve numerical problems involving rate of reaction at any
given time.

5. INTRODUCTION
The rate of reaction refers to:
 The speed at which the reactants are converted into products in a
chemical reaction.
 The observable change in quantity of a reactant with time.
 The observable change in quantity of a product with time.
Rate of reaction:
Observable change in quantity of reactant/ product
Time taken for the change to occur
The quantity of reactants and products refers to:
 Mass of solids
 Concentration of liquids
 Volume of gases

6. Continue…
Example: Reaction between marble chips (calcium carbonate)
and dilute acid.
CaCO3 (s) + 2HNO3 (aq)  Ca(NO3)2 (aq) + H2O (l) + CO2 (g)
Reactants Products
 In this reaction, the observable change are:
 A decrease in mass of the reactant, CaCO3 with time.
 The volume of carbon dioxide gas produce increase with time.
The rate of reaction inversely proportional with time.
 Explanation:
 A reaction is fast, or its rate of reaction is high, if the time taken for
the reaction to occur is short.
 Likewise, a reaction is slow, or its rate of reaction is low if the time
taken for the reaction to occur is long.

7. Fast Reactions
Type of Reaction Example
Burning • Sodium burns rapidly in air to form sodium oxide.
4Na (s) 2Na2O (s)
Reaction between • Dilute acid react with carbonates to release carbon
dilute acids and dioxide.
carbonates 2HCl + CaCO3 (s)  CaCl2 (aq) + H2O + CO2
Reaction between a • Very reactive metals like potassium and sodium
reactive metal and react vigorously with water to release hydrogen gas.
water or dilute acids 2K (s) + 2H2O (l)  2KOH (aq) + H2 (g)
• Mg, Zn and Al react with dilute acids to release
hydrogen gas rapidly.
Mg (s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)
Precipitation of ionic When barium(II) chloride, BaCI2 and potassium
compounds chromate(vl), K2CrO4 solution are added together, a
yellow precipitation of barium chromate (vI), BaCrO4 is
formed immediately.

8. Slow Reactions
Type of Example
Reaction
Precipitation of • A slow reaction occurs when a dilute acid is added to
sulphur sodium thiosulphate solution Na2S2O3. A yellow
precipitation forms after several seconds.
Na2S2O3(aq) + 2HCl(aq)  2NaCl(aq) + S(s) + H2O(l) + SO2(g)
Photosynthesis • Carbon dioxide and water combine in the presence of
chlorophyll and sunlight to form glucose and oxygen in
green plants. This process occurs slowly.
Rusting • Iron rusts slowly in the presence of water and oxygen to
form hydrated iron(II) oxide, Fe2O3.H2O or rust.