*(REDO LATER)* Lecture 29 Flashcards
1
Q
State collision theory
A
For a reaction to occur:
- Reactant particles must collide
- Collisions must have a minimum amount of energy (activation energy: Ea)
- Reactants may require a specific orientation
2
Q
what does a PE diagram map?
A
- change in PE for a reaction as it progresses from reactants to products
- start with PE due to all chemical bonds in reactants (PEreactants)
- end with PE due to chemcail bonds in products (PEproducts)
- for reaction to occur the activation energy must be overcome
3
Q
Draw a potential energy diagram for
- endothermic reaction
- exothermic reaction
- reaction with a catalyst
A
- see notes for answer
4
Q
List the factors that impact reaction rates (4)
A
- Physical nature: gasses react faster; smaller particles –> more surface area –> react faster
- reactant concentration: increasing reactants increase reaction rate (more particles = greater chance of collision)
- reactant temp (increase in KE=moves things faster= more collisions)
- catalyst presence: speeds up reaction rate by lowering activation energy requirement
5
Q
define: catalyst
A
- substance that when added to a chemical reaction speeds up rate of reaction but is itself unchanged after the reaction is completed
- Lowers the activation energy of a reaction
- Provides an alternate pathway for the reaction
6
Q
Chemical equilibrium
A
- 2 opposing chemical reactions occur simultaneously and at the same rate
- by convention, write the favourable or desired reaction as the forward reaction
7
Q
Describe the sequence of reactions
A
At the start of there is a:
- high concentration of reactants
- low concentration of products
as it progresses:
- concentration of products increase
- concentration of reactants decrease
8
Q
How does changing concentration impact the rate of forward and reverse reactions
A
- as the concentration of reactants decreases the rate of forward reaction decreases
- as the concentration of products increases the rate of reverse reaction increase
9
Q
when is equilibrium established?
A
- rate of forward and reverse reactions are the same
- reaction is “over”
- concentration of all species are constant
10
Q
can you draw the variation of concentration with time? what about variation of forward and reverse reaction rates?
A
see notes
11
Q
what does Keq represent?
A
- relates the concentration of reactants and products at equilibrium
- It gives information about the extent to which reaction has occurred
- product over reactants
- unitless
12
Q
what causes keq to vary?
A
- temperature
13
Q
Describe the relative amounts of reactants and products and the equilibrium position when keq is:
very large large near unity small very small
A
- almost all product; far right
- products>reactants; right
- products ~=~ reactants; neither right nor left
- reactants>products; left
- almost all reactants; far left
14
Q
State Le Chatelier’s Principle
A
- stress applied to a system in equilibrium will cause the position of equilibrium to shift to best reduce stress
15
Q
When does pressure change impact equilibrium?
A
- only when gases are involved and when pressure change is due to a change of volume
- decrease pressure means increase in volume
- pressure increase means system will shift toward side with less moles of gas
