CHEMISTRY Form 5

Chapter 1: Rate Of Reaction What is rate of reaction?

-the speed which the reacyanys are converted into product in a chemical reaction Formula?

Rate Of Reaction = amount of reactant used up Time taken

Rate Of Reaction = amount of product formed Time taken

Terms?-For Rate Of Reaction __ High __Low-For Reaction__Fast __ Slow

Observable Changes And Measuring-Volume Of Gas Liberated-Precipitate Formation-Change In Mass During The Reaction-Colour Change -Temperature Change- Pressure Change

Example of SLOW reaction

Rusting Of IronGrowthPhotosynthesis

Example of FAST reaction

Reaction Of Magnesium And OxigenFireworks

Rate Of Reaction?-Average Rate Of Reaction – The average value of rate of reaction within a specified period of time

Example;5g of Magnesium Ribbon is completely burned in 2 seconds. Calculate the average rate of reaction.

Time(s) 0 10 20 30 40 50 60Volume Of Gas(cm3) 0 30 50 65 75 75 75

Solution

Average Rate Of Reaction = 75 40

=1.875cm3s-1

5 Factor Affecting Rate Of Reaction-Total Surface Area Of Solid Reactant When a fixed mass of solid reactant, the smaller size of the reactant, the higher will be the total surface exposed area. Thus the higher will be the rate of reaction-Concentration Of Reactant (LIQUID) When theconcentration of the reactant increases, the rate of reaction become higher-Temperature Of Reactant As the temperature of the reactant increases, the rate of reaction also increases-Use Of Catalyst *Catalyst = is a substance which alters the rate off chemical reaction while it remains chemically unchange at the end of the reaction Positive Catalyst increase the rate of reaction by lowering the activation energy-Pressure Of Gaseous Reactant

Collision Theory

Definitions-Activation Energy = is the minimum amount of energy to start a reaction-Effective Collision = collision which result in chemical reaction and its formation of product

-Frequency Of Effective Collision = number of collision per unit time( nt ) According to collision theory, for the reaction to occur, the reactant must:

-Collide between each other-Collide with enough amount of energy (achieve the activation energy )-Collide with correct orientation

Collision Theory And Factor Affecting The Rate Of Reaction

When the size of the solid is small, the total surface area is high, this cause the frequency of collision increases,thus the frequency of effective collision also increses. As a result, the rate of reaction is higher

Effect Of The Surface Area

When the concentration of solution reactant is high, number of particle per unit volume increses, this cause the frequency of collision increases, thus the frequency of effective collision also increases. As a result, the rate of reaction is higher

Effect of Concentration and Pressure

When the temperature increases, the kinetic energy of reacting particles increases, the particle collide more often (the frequency of collision increases ),thus it increases the frequency of collision. As a result, the rate of reaction is higher

Effect of Temperature

The presence of catalyst in chemical reaction lowering the activation energy ,this cause more colliding particle able to achieve lower activation energy (frequency of collision inncreases), thus frequency of effective collision increases. As a result,the rate of reaction is higher

Effect Use Of Catalyst