10.1 Reaction rates and equilibrium
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The rate of a chemical reaction measures…
…how fast a reactant is being used up or how fast a product is being formed.
What can the rate of a reaction be defined as
The change in concentration of a reactant or a product in a given time
rate =
change in concentration / time
What are the units of rate of reaction
mol dm^-3 s^-1
The rate of a reaction is fastest at the _______ of the reaction as each reactant is at its _______ concentration.
Fastest Highest
The rate of a reaction ______ ______ as the reaction proceeds because the reactants are being ______ ______ and their concentration ______.
Slows Down Used Up Decreases
Once one of the reactants has been completely used up, the concentrations ______ ______ and the rate of reaction is _______.
Stop Changing Zero
Factors that can change the rate of reaction
Concentration (or pressure when reactants are gases) Temperature Use of a catalyst Surface area of solid reactants
What does the collision theory state
That two reacting particles must collide for a reaction to occur.
A collision will be effective if two conditions have been met:
The particles collide with the correct orientation The particles have sufficient energy to overcome the activation energy barrier of the reaction
How does increasing the concentration affect the rate of reaction
When concentration is increased, the rate of reaction generally increases. Increases the number of particles in the same volume, particles closer together and collide more frequently. Therefore more effective collisions in given time
How does increasing the pressure of a gas affect the rate of reaction?
When a gas is compressed into smaller volume, pressure increases and rate of reaction increases. Concentration increases as same number of gas molecules occupy smaller volume. Gas molecules closer together and collide more frequently, therefore more effective collisions in same time
How to monitor the progress of a chemical reaction
Monitor the removal (decrease in concentration) of a reactant Following the formation (increase in concentration) of a product
Methods that can be used to determine the rate of reaction where a gas is produced
Monitoring the volume of gas produced at regular time intervals using gas collection Monitoring the loss of mass of reactants using a balance
What is volume of gas produced and mass loss both proportional to
The change in concentration of a reactant or product
Method - Monitoring the production of a gas using gas collection Decomposition of hydrogen peroxide 2H2O2 –MnO2 catalyst–> 2H2O + O2
• Hydrogen peroxide is added to the conical flask and the bung is replaced • Initial volume of gas in measuring cylinder is recorded • Manganese dioxide catalyst is then added to conical flask and bung is replaced. Stop clock is started • The volume of gas produced in the measuring cylinder is recorded at regular intervals until the reaction is complete • The reaction is complete when no more gas is produced • Plot graph of total volume of gas produced against time • To calculate initial rate, draw tangent at t=0
Equation for the reaction of calcium carbonate and hydrochloric acid
CaCO3 + 2HCl –> CaCl2 + CO2 + H2O
Monitoring the loss of mass of reactants using a balance
Carbonate and acid are added to conical flask on a balance Mass of flask and contents is recorded initially and at regular time intervals. Reaction is complete when no more gas is produced so no more mass is then lost. Graph of mass lost against time is plotted