(Topic 6) Rate And Extent Of Chemical Change (CGP book) Flashcards
What is rate of reaction?
How fast the reactants are changed into products
Examples of rates of reaction?
Slow - Rusting
Moderate - Magnesium and acid
Fast - Burning and explosions
How to find rate of reaction?
Amount of product formed or reactant used up over time
Rate of reaction graphs?
Steeper line - faster rate of reaction
Over time line plateaus as reactants are used up
What is collision theory?
Collision frequency - More collisions there are, the faster the reaction
Energy transferred - Particles have to collide with enough energy to have a successful collision
What does rate of reaction depend on?
Temperature
Concentration of solution / pressure of gas
Surface area
Catalyst
How to increase rate of reaction?
Increase temp
Increase concentration/ pressure
Decrease surface area in which particles are
Use a catalyst
What is used to measure rate of reaction?
Gas = cm*3
Solid = (g)
Seconds = (s)
How to calculate mean rate of reaction from a graph?
Change in y / change in x
What is required for equilibrium to occur in a reversible reaction?
A closed system - no reactants of products can escape and nothing else can get in
Steps of a reversible reaction?
- reactants react, their concentrations fall so forward reaction slows down
- as more and more products are made, their concentrations rise so backward reaction speeds up
- eventually, both are at same speed so system is at equilibrium
What happens at equilibrium?
Both forward and backward reactions are happening, but there is no overall effect, meaning concentrations of reactants and products have reached a balance and won’t change
What happens if equilibrium is at right?
Concentration of products is greater than reactants
What happens if equilibrium is at left?
Concentration of reactants is greater than that of products
What does the position of equilibrium depend on?
Temperature
Pressure
Concentration of reactants and products
What is le chateliers principle?
The idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract that change
Can be used to predict effect of any changes you make to a reaction system
What happens if you decrease temperature in a reaction?
Equilibrium will move to exothermic direction to produce more heat, this means you will have more products for exothermic reaction and fewer for endothermic
What happens if you raise temperature in a reaction?
Equilibrium moves to endothermic direction to try and decrease it, this means you will get more products for endothermic reaction and fewer for exothermic
What happens to equilibrium if you change the pressure in a reaction?
(Only works for gases)
Increase - equilibrium tries to reduce so moves in direction of fewer molecules of gas
Decrease - equilibrium tries to increase sp moves in direction of more gas molecules
What happens to equilibrium in a reaction if you change concentration?
- change concentration of reactants or products, system no longer at equilibrium
- system responds to bring back equilibrium
Increase reactants - system tries to decrease by making more products
Decrease products - system tries to increase by reducing amount of reactants
