Topic 6 Rate and extent of chemical change Flashcards
What is the definition of rate of reaction
The rate of reaction is the speed at which reactants are converted into products.
Rate= amount of reactant used or amount of product formed / time taken
What do the lines represent in a graph
The steepest line is the quickest reaction
The bottom line has the slowest rate of reaction
What is the collision theory
The more collisions there are the faster the rate of reaction
What are the units for rate of reaction
Mass= Grams
Volume of Gases= Cm3
Conc= Mol/dm3
Time=seconds
4 mains factors effecting rate of reaction
Temp increased kinetic energy more frequent collisions
Conc more particles in same space more collisions
Surface area more exposed particles more collisions
Catalyst speeds up reaction without being used has a lower activation energy
How does temp affect rate of reaction
Particles move faster
more frequent collisions
More energy more collisions
How does Conc and pressure effect rate
High conc more particles in same volume more frequent collisions
Higher pressure more particles closer together more frequent collisions
How does an increased surface area effect rate
Solid breaks into smaller pieces causes increase surface are to volume ratio therefore more particles are exposed more frequent and faster collisions
How do catalyst increase rate and give examples
Lower activation energy
Not used up
Example iron (harber process)
Enzymes biological catalyst
3 ways to measure rate of reaction
Measuring mass change
Measuring gas volume
Colour change
How does the magnesium and acid experiment measure rate
Mg reacts with hydrochloric acid producing hydrogen gas
Measure volume of gas collected over time
Faster reaction=more gas collected innless time
What is the change in mass practical
What is a reversible reaction
A reaction that can go forwards and backwards
what does this mean ⇋
reversible reaction
What happens in a closed system at equilibrium
Forward and reverse reaction happen at same rate
Conc of reactants and products remain constant
This is called dynamic equilibrium
What is Le Chatelier principle
If conditions are changed system will shift and try to counteract the change
How does changing concentration affect equilibrium?
Increase reactant concentration → Shifts right (more products).
• Increase product concentration → Shifts left (more reactants)
How does temperature affect equilibrium?
Increase temperature → Favours endothermic reaction.
• Decrease temperature → Favours exothermic reaction
How does pressure affect equilibrium in gases?
Increase pressure → Shifts to side with fewer gas molecules.
• Decrease pressure → Shifts to side with more gas molecules.
How does a catalyst affect equilibrium?
A catalyst speeds up both forward and reverse reactions equally.
• It does not change equilibrium position but allows equilibrium to be reached faster.
