Topic 16 Flashcards
1
Q
###
- Uses for methanol and ethanol
- Reforms them to use hydrogen
- Alcohol is oxidised at the anode with water present
- CH2OH + H20 → CO2 + 6e- + 6H+
- H+ ions then pass through electrode
- 6H+ + 6e- + 1.52 → 3H2O
A
- Uses for methanol and ethanol
- Reforms them to use hydrogen
- Alcohol is oxidised at the anode with water present
- CH2OH + H20 → CO2 + 6e- + 6H+
- H+ ions then pass through electrode
- 6H+ + 6e- + 1.52 → 3H2O
2
Q
What is the rate equation?
A
- Describes the relationship between the rate of a chemical reaction and the concentrations of its reactants
- Allows for determining the changes in concentration of reactants affect the rate of reaction
3
Q
What does rate of reaction mean?
A
- AKA Overall rate of reaction
- How product increases with time
- How a reactant decreases over time
- Negative sign in second formula reflects that the reactant is decreasing
- Giving a positive value
4
Q
What is the rate equation?
A
- Describes the relationship between the rate of a chemical reaction and the concentrations of its reactants
- Allows for determining the changes in concentration of reactants affect the rate of reaction
5
Q
What is the rate constant?
A
- The rate constant represents the rate of the reaction when all reactants are present at a concentration of 1 mol/L.
- Its value depends on the temperature, pressure, and presence of any catalysts or inhibitors.
- The rate constant is generally temperature-dependent, with the rate constant increasing as the temperature increases.
- A higher value of the rate constant implies that the reaction will occur more quickly at a given set of concentrations.
- A lower value of the rate constant implies that the reaction will occur more slowly at the same set of concentrations.
6
Q
What are the units of rate contestants?
A
Found through rearranging the rate equation
7
Q
How do you find the overall order of a rate equation?
A
8
Q
What does it mean by rate determining?
A
- Slowest step in a chemical reaction that determines the overall rate of the reaction.
- Typically the step with the highest activation energy
- Important for understanding the kinetics of a reaction and for optimizing reaction conditions to improve reaction efficiency
- Increasing the concentration of a reactant involved in the rate-determining step or by adding a catalyst the RDS is sped up
9
Q
What does it mean by half-life?
A
- Time taken for the concentration of the reactant
- To fall to one-half of its initial value
10
Q
What are homogeneous catalysts?
A
A catalyst that is in the same phase as the reactants
11
Q
What are heterogeneous catalysts?
A
- A catalyst that is in a different phased as the reactants
- Used in the Haber process an the contact process
12
Q
What is the definition of activation energy?
A
- Minimum amount of energy that reactant molecules must possess
- In order to undergo a chemical reaction
- Energy required to break the bonds of the reactant molecules and initiate the reaction
- Barrier that must be overcome for a reaction to occur
13
Q
How do you calculate the rate of reaction
A
- Construct rate equation
- Substitute numbers Rate = K[NO]2[O2]1
- Plug in numbers
14
Q
How do you calculate the rate constant from the rate equation?
A
15
Q
What is the rate equation for 0 order?
A
16
Q
What is the rate equation for 1st order?
A
17
Q
What is the reaction for 2nd order?
A
18
Q
What is the reaction for 3rd order?
A
19
Q
What is the continuous method?
A
- Determines rate of equation
- One reaction mixture is made up
- Samples are withdrawn at regular intervals
- To measure the concentration
- Then the reaction is stopped by quenching
20
Q
What are the step in the continuous method?
A
- Draw a concentration-time graph
- Find the half life of the reaction at different concentrations
- Then determine the order of the reaction based of the half life
21
Q
What are the step in the continuous method?
A
- Draw a concentration-time graph
- Find the half life of the reaction at different concentrations
- Then determine the order of the reaction based of the half life
22
Q
What are the different conc graphs for each order and the relevant half life for each?
A
23
Q
How do you calculate rate form a concentration time graph?
A
- Draw a tangent on curve at the given time
- Then find the gradient of the tangent
- x / y = rate
24
Q
How do you calculate rate from a volume time graph?
A
- Find tangent on curve at given time
- Find the gradient of the tangent
25
What is a clock reaction?
26
What are the assumptions with the clock reaction?
1. Temperature of the reaction remains constant
2. Conc of reactions doesn’t change significantly during the time of the reaction
3. Reaction has not proceeded too far when the end point is seen
- This allows for the rate of reaction to stay constant
- Resulting in a good estimate of the initial rate of reaction
27
What is the initial rate method?
- Several reaction mixtures are made up
- Initial rate is measured
- Initial rate = Time for fixed amount of reactant to be used (vise versa for products)
- Then able to calculate mathematical relationship between the two
28
What are the different rate graphs for each order and the relevant half life for each?
29
What is a elementary reaction?
30
How do you form a RDS from a rate equation?
31
What can you deduce from this rate equation?
32
What are SN1 mechanisms?
33
What are SN2 mechanisms?
34
What is the Arrhenius equation
35
How do you simplify the Arrhenius equation?
36
How do you work our activation energy using Arrhenius plots?
