The Rate and Extent of Chemical Change Flashcards
How do we measure the rate of a reaction?
- Measuring how fast the reactants are used up
or - Measuring how fast the products are forms
Rate of Reaction Equation
Quantity of Reactants used up (g or cm3) /Time Taken (s)
Rate of Reaction Equation 2
Quantity of Products Formed (g or cm3) /Time Taken (s)
Mass of reactant on a graph
- At first decreases rapidly
- Slows as reaction progresses (reactant gets used up less quickly)
- Mass of reactant is 0
Volume of product on a graph
- Starts at 0 (no products yet)
- Quickly increases as product is formed
- Graph becomes less steep
- Eventually plateau’s (levels off) when a reactant is used up
What affects the rate of a reaction?
- Temperature
- Surface Area
- Absence/Presence of catalysts
- Concentration/Pressure
Collision Theory
For particles to react, they have to collide with each other with a sufficient amount of energy
What factors affect collision theory?
- Amount of energy the particles have (more energy means more energy transfer during collisions)
- Frequency of collisions (more frequent collisions mean more successful ones)
How does temperature increase rate of reaction?
- Temp. increase means particles gain more energy
- Particles move faster
- More frequent collisions
- Collide with more energy
- More likely to exceed activation energy
- More successful collisions
How does concentration/pressure increase rate of reaction
- Increase in concentration/pressure means increase in particles (per unit of volume)
- More frequent collisions
- More successful collisions
- Increase in reaction rate
How does surface area increase rate of reaction?
- Increase in surface area means higher SA:V ratio
- More frequent collisions
- Higher rate of successful collisions
Catalyst
Substances that speed up rate of reaction without being used up (aren’t included in the reaction equation)
How do catalysts increase rate of reaction?
- Lower activation energy by providing alternative reaction pathways
What is a Reversible Reaction?
A chemical reaction that can happen in both directions
What is Equilibrium?
When the concentrations of the forward and backward reactions of a reversible reaction remain constant