L14 + L15: Reaction Kinetics I & II Flashcards
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?
Rate of concentration change of reactants (A) and products (P)
Equation for rate of reaction
Rateofreaction=
Δt/Δ[Product, A] =
− Δt/Δ[Reactant, P]
[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?
Rate is independent of the reactant concentration, the reaction proceeds at constant rate, no matter how much reactant is present
Equation for first order rate
Rate = k(A)¹
What characterizes a zero-order reaction in terms of its rate equation?
The reaction rate is independent of reactant concentration
How does reactant concentration affect the rate of a reaction?
Increases the rate of reaction
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 distinguishes first-order reactions from zero-order reactions in their rate equations?
The rate of first-order reactions depends on reactant concentration
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 zero order reaction & units
rate = k
mol dm⁻³ s⁻¹
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 the difference between first-order and second-order reactions in terms of their rate equations?
First-order reactions depend linearly on reactant concentration, while second-order reactions depend on the square or product of reactant concentrations.
When does zero-order reactions occur?
1) enzyme-catalysed reactions
2) reactions on solid surfaces
3) photochemical reactions
Why is half-life measured?
Initial rate is difficult to measure
Equation for rate of pseudo-first order equation
Rate = k (A)¹ (B)¹
