Chemistry: Rate Equations
This flashcard set focuses on the fundamentals of reaction rates, including the definition and units of rate, the necessity of particle collisions with sufficient energy, and the concept of activation energy as the minimum energy needed to initiate bond breaking in a reaction.
Rate of reaction
The change is concentration of a substance in a given time
Key Terms
Rate of reaction
The change is concentration of a substance in a given time
Units of rate
Moldm-3s-1
Reactions can only occur when…
Collisions take place between particles having sufficient energy
What is the sufficient energy called
Activation energy
Activation energy
The minimum energy required to start a reaction by the breaking of bonds
How does increasing conc increase rate of reaction
more particles in given volume
- more frequent successful collisions
Related Flashcard Decks
Study Tips
- Press F to enter focus mode for distraction-free studying
- Review cards regularly to improve retention
- Try to recall the answer before flipping the card
- Share this deck with friends to study together
| Term | Definition |
|---|---|
Rate of reaction | The change is concentration of a substance in a given time |
Units of rate | Moldm-3s-1 |
Reactions can only occur when… | Collisions take place between particles having sufficient energy |
What is the sufficient energy called | Activation energy |
Activation energy | The minimum energy required to start a reaction by the breaking of bonds |
How does increasing conc increase rate of reaction |
- more frequent successful collisions |
How does increasing pressure increase rate |
|
How does increasing SA of a solid increase rate | Powders increase SA- more frequent successful collisions |
How does increasing temp increase rate | (Maxwell Boltzmann) more particles with energy equal to or greater than Ea so more successful collisions |
How does a catalyst increase rate | Provides alternative pathway with lower Ea so far more molecules have Energy equal to or greater than activation energy |
what does the rate equation show | the relationship between the rate of a reaction and the initial conc of the reactants |
general rate equation | rate= k[A]m [B]n |
what is [A] in rate equation | conc of A |
what is [B] in rate equation | conc of B |
what is m in rate equation | order with respect to A |
what is n in rate equation | order with respect to B |
what is k in rate equation | rate constant |
what is the overall order of a reaction | the sum of the individual orders |
half life | the time taken for the concentration of a reactant to half |
how would zero order be shown on a conc-time graph | straight line indicating uniform day |
how would first order be shown on a conc time graph | curve- equal half lives |
how would second order be shown on a conc time graph | steeper curve- half lives increase |
what is the gradient at a particular time on a conc time graph a measure of | the rate at that time |
how to determine order of ror with a conc time graph |
|
how can rate-conc graph be plotted |
|
rate graph zero order | flat line |
rate graph first order | straight diagonal line, positive gradient |
rate graph second order | curve |
what is k | a proportionality constant that links rate of reaction with the concentrations of reactants |
correlation between value of k and rate | k larger- faster rate |
what do the units of k depend on | overall order of reaction |
what do chemical reactions often take place in | a series of steps called the reaction mechanism |
what can the rate equation provide clues about | a likely reaction mechanism by identifying slowest stage of a reaction sequence |
rate determining step | slowest step in a reaction mechanism |
what will any step that occurs after rate determining step not affect | overall rate- reactants involved in later steps wont appear in rate equation |
how can you tell if the reaction is a one step process | the powers in the rate equation match the stoicheometry of the overall equation |
how can you tell if the reaction has more than one step | the powers of the rate equation don't match the overall equation |
what always increases when temperature is increased | the rate of reaction- Maxwell districution |
if the temperature is increased in a reaction, why must k increase as rate increases | if [A] and [B] are kept constant k must increase | rate=k[A]m[B]n |
what is the increase of k with temperature | exponential |
what is the relationship between rate constant and temp described by and what does it allow us to work out | Arrhenius equation | allows us to work out Ea |
the Arrhenius equation | k=Ae^-Ea/RT |
what does k mean in Arrhenius equation | rate constant |
what does A mean in Arrhenius equation | Arrhenius constant |
what does ea mean in Arrhenius equation and units | activation energy (J) |
what does R mean in Arrhenius equation | ideal gas constant |
what does t mean in Arrhenius equation and units | temperature (K) |
how can the Arrhenius equation be rearranged | by taking the natural log (ln) of both sides |
Arrhenius equation rearranged | lnK=lnA -Ea/RT |
what form can rearranged Arrhenius equation rearranged be expressed in | y=mx+c |
how can Arrhenius equation be used to determine the activation energy of a reaction |
|