L14 + L15: Reaction Kinetics I & II Flashcards
(27 cards)
Equation of Gibbs Free Energy
ΔG=ΔH−TΔS
ΔG = Gibbs free energy change.
ΔH = Enthalpy change (heat change).
TΔS = Temperature × Entropy change (disorder).
For a reaction to be spontaneous does ΔG have to be neg/pos?
If ΔG is negative, the reaction is thermodynamically favorable.
3 factors that rate of a reaction can be changed by
1) change of temp
2) reactant conc/partial pressure
3) addition of catalyst
What is rate of reaction defined as?
Change in concentration of a reactant/product per unit time
Equation for rate of reaction
Rateofreaction:
Δ(product)/Δtime = −Δ(reactant/Δtime
[A] decreases over time, [P] increases over time.
What does reaction rate measure?
How fast reactants are converted to products
Equation for rate
Relates the reaction rate to reactant concentrations:
Rate=k[A]ˣ
k = Rate constant.
[A] = Reactant concentration.
x = Order of the reaction.
What is zero order?
Give:
1) Equation
2) Graph plot
3) Half life
Rate is constant no matter how much reactant is added
1) Rate = k
2) [A] vs time
3) Decreases
What is first order rate?
Give:
1) Equation
2) Graph plot
3) Half-life
Cares proportionally about concentration, rate depends on [A]
1) Rate = k[A]
2) ln[A] vs time
3) Constant half-life
What is second order rate?
Give
1) Equation
2) Graph plot
3) Half life
Rate depends on [A]² & [A][B]
1) Rate = k[A]², k[A][B]
2) 1/[A] vs time
3) Increases
What factors can change the rate of a chemical reaction?
Change of temperature
How do you determine the order of a reaction experimentally?
By measuring initial rate with varying reactant concentrations
What is the relationship between half-life and reaction order?
Half-life is dependent on the reaction order
What is the role of catalysts in changing reaction rates?
Catalysts lower the activation energy, increasing reaction rates
What happens to the rate of reaction when temperature is changed?
The rate of reaction increases or decreases
What does it mean for a reaction to be thermodynamically favorable?
The reaction has a negative Gibbs free energy
How does the concentration of products change over time during a reaction?
Increases over time
How does the concept of half-life apply to reaction kinetics?
It can be used to ascertain the reaction order
How does the Gibbs free energy relate to the spontaneity of a reaction?
It must be a negative value for a process to occur naturally
Equation of rate in first order reaction and units
rate = k (A)
s⁻¹
Equation of rate in second order equation and units
rate = k (A) (B)
mol⁻¹ dm⁻³ s⁻¹
Equation of rate in third order equation and units
rate = k (A) (B)²
mol⁻² dm⁻⁶ s⁻¹
What is half life?
Time taken for the initial concentration of the reactants to decrease by half
Equation for rate of pseudo-first order equation
Rate = k (A)¹ (B)¹
