rate equations Flashcards
What is the rate of a chemical reaction?
A measure of how fast a reaction takes place, defined as the change in concentration of a reactant or product per unit time.
Units: mol dm^-3 s^-1
What is activation energy?
The minimum energy required for particles to collide and react.
It is a key concept in collision theory.
What does the Maxwell-Boltzmann distribution indicate about particle energies?
Particles do not all have the same energy; no particles have 0 energy, and only a small number have energy greater than or equal to the activation energy.
What happens to the Maxwell-Boltzmann curve when temperature increases?
The curve shifts to the right, indicating more particles have energy greater than or equal to the activation energy.
How does increasing the concentration of a solution affect the reaction rate?
Higher concentration leads to a faster reaction because particles are closer together, increasing the likelihood of collisions.
What effect does surface area have on the rate of reaction?
Greater surface area results in a faster reaction due to more exposed particles available for collision.
How does pressure affect the rate of gas reactions?
Higher pressure leads to a faster reaction because particles are closer together, increasing successful collisions.
What is the effect of temperature on the rate of reaction?
Higher temperature results in a faster reaction as particles have more energy and move faster, leading to more successful collisions.
What is the role of a catalyst in a chemical reaction?
A catalyst increases the rate of reaction without being used up by providing an alternative pathway with lower activation energy.
How can the rate of a reaction be determined from a graph?
By calculating the gradient of a line of best fit or tangent on the graph.
Units are derived from the y-axis divided by the x-axis.
What does the rate equation look like?
RATE = k[A]^m[B]^n
Where k is the rate constant, m and n are the orders of reaction.
What is the significance of the rate constant (k)?
It links the rate of a reaction to the concentrations of reactants, with larger k indicating a faster reaction.
How does temperature affect the rate constant (k)?
k increases with temperature, as higher temperatures lead to increased kinetic energy and more frequent successful collisions.
Define zero order in terms of reaction rate.
If concentration changes, there is no effect on the rate; the rate remains constant.
Define first order in terms of reaction rate.
Changes in concentration result in a proportional change in rate; if concentration doubles, rate doubles.
Define second order in terms of reaction rate.
Changes in concentration result in a squared change in rate; if concentration doubles, rate quadruples.
What is the relationship between the coefficients in a chemical equation and the rate expression?
The coefficients in the chemical equation do not necessarily appear in the rate expression; zero orders do not appear.
How can concentration-time graphs be used to determine reaction order?
A straight line indicates zero order, while a curve could indicate first or second order.
What is the initial rates method?
A series of experiments at constant temperature with varying concentrations to measure initial rates and plot concentration-time graphs.
What is the Arrhenius equation used for?
It shows the link between the rate constant, activation energy, and temperature.
What does a large activation energy (Ea) imply for the rate of reaction?
A large Ea results in a smaller rate constant (k) as fewer particles have energy greater than Ea.
What does the gradient of an Arrhenius plot represent?
The gradient represents the activation energy (Ea) of the reaction.
What is the rate-determining step (RDS)?
The slowest step in a multi-step reaction that governs the overall rate of the process.
