S3 Speed Of Reaction Flashcards
What are the 3 ways to measure speed of reaction?
1) amount of reactants used/time taken
2) amount of product obtained/time taken
3) volume of gas produced/time taken
What is gradient maximum?
It is the maximum speed of a reaction at the moment 2 reactants are added.(time=0)
How do you deduce speed of reaction based on a graph?
Gradient.
Steep gradient:faster reaction
Gentle gradient: slower reaction
Gradient=0: reaction completed
How to deduce yield (amount of product formed) based on a graph?
Read off the y-axis.
Higher value: more product
Lower value: lesser product
Explain the collision theory.
Molecules are in constant random motion, and since the formation of bonds require atoms to come close together, reactions require collisions between reactant molecules.
What are ineffective collisions?
Unsuccessful collisions where no products are formed, and where molecules simply hit and rebound.
Define effective collisions.
Effective collisions are collisions that lead to formation of products. The particles must collide with a minimum activation energy to break bonds in the colliding molecules, resulting in a reaction forming new products.
What are the 5 factors affecting the rate of reactions?
1) pressure
2) particle size (surface area)
3) temperature
4) concentration
5) catalysts
How does increasing concentration of a reactant result in increased rate of reaction?
Increased concentration leads to increase in number of particles per unit volume. This increases the frequency of effective collisions and thus increasing the rate of reaction.
How does increasing pressure increase rate of reaction?
Increased pressure leads to more particles closely packed together in a given volume. This increases the frequency of effective collisions and thus increasing the rate of reaction.
How does increasing surface area increase the rate of reaction?
Increased surface area means that there is a greater surface area for collisions. This increases the frequency of effective collisions and thus increasing the rate of reaction.
How does increasing the temperature increase rate of reactions?
Increased temperature means that more heat energy is being converted to kinetic energy. This increases the frequency of effective collisions and thus increasing the rate of reaction.
Why will a reaction stop? (When a certain product is insoluble)
An insoluble layer of the insoluble product will coat around the reactant, preventing further reactions, thus stopping the reaction.
Use ideas of activation energy to explain the function of an enzyme.
Enzymes decrease the activation energy needed for a reaction by providing an alternative pathway. Thus, when no enzyme is used, particles need to collide with more energy to overcome the activation energy.
Define a catalyst.
A catalyst is a substance which increases the speed of a chemical reaction and remain chemically unchanged at the end of the reaction.
