Rates of Reactions

Equation for Rate

Change in conc/ time

When is rate the fastest

conc of reactants is highest

When does rate start slowing down?

When the concentration of reactants decreases

When is Rate 0

once reactants are used up

How are rates calculated?

by measuring amount of reactants used up or amount of product formed over period of time

What does the gradient represent

the initial rate of reaction

What do we do to find reaction at a given time

draw a tangent at that given time

Factors affecting rates of reactions

Concentration of solution

Surface Area

Temperature

Catalyst

Pressure

Light in some

What is the collision theory

For a chemical reaction to take place, reacting molecules must collide effectively.

What is the reaction a measure of?

how frequently successful collisions occur

For collisions to be effective, molecules must collide in the

correct orientation

sufficient energy

Define activation energy

minimum energy needed for a reaction to occur

Any __________ that increases chance of ___________ collisions, also increases ___________________.

factor

effective

rate of reaction

Exothermic

Endothermic

Exothermic Reactions

Products have less energy than reactants

Excess energy is lost from reaction as heat

∆H is negatibe

Endothermic Reactions

Energy of products is more than reactants

Heat is taken in from surroundings

∆H is positive