Chemical Kinetics Flashcards
When is the value for rate negative?
Never. The value for rate of reaction should always be positive
What are the requirements for particles to react?
- Reactants must collide
- Reactants must collide with adequate activation energy
- Reactants must collide with the correct orientation
What is activation energy equal to?
The energy difference between the reactants and the transition state
What is the Arrhenius equation and what does each symbol represent?
k = A e^-Ea/RT
k = rate constant
A = pre-exponential factor
Ea = activation energy (in the same units as R*T)
R = universal gas constant (8.314)
T = temperature (in Kelvin)
How can you work out activation energy from a graph?
For graphs of 1/T against ln(k), the gradient = -Ea/R. So gradient x R = -Ea
How does rate change if conc doubles 0 order?
Conc doubles, rate is not affected
How does rate change if conc doubles 1st order?
Conc doubles, rate doubles
How does rate change if conc doubles 2nd order?
Conc doubles, rate quadruples
What is the rate equation for reaction A + B -> X?
Rate = k [A]^m [B]n
Where m is the reaction order wrt A, and n is the reaction order wrt B
Are catalysts included in the rate equation?
Catalysts can be included in the rate equation if they are a reactant in the rate determining step (however to be a catalyst they must somehow be regenerated)
How can you determine the order of a reactant?
The orders of reactants can only be determined experimentally; they have nothing to do with the number of moles in the balanced equation
What is the rate constant equal to?
K = rate / [A]^m [B]^n
What are the units for zero order reactions?
mol L-1 s-1
What are the units for first order reactions?
s-1
What are the units for second order reactions?
L mol-1 s-1
