Kinetics Flashcards
How does temperature affect the Maxwell-Boltzmann distribution?
Higher temperatures shift the distribution, increasing the number of molecules with energy greater than the activation energy.
What does the Maxwell-Boltzmann distribution explain in a reaction?
It shows the distribution of kinetic energy among molecules and the fraction of molecules with enough energy to overcome activation energy.
What does an enthalpy profile show?
It shows the energy changes during a reaction, including activation energy and whether the reaction is exothermic or endothermic.
What is activation energy?
The minimum energy required for reactant molecules to successfully collide and form products.
What is required for a collision to result in a reaction?
- Sufficient kinetic energy (activation energy).
2.Proper orientation of particles.
What is the role of a catalyst in a chemical reaction?
A catalyst provides an alternative pathway with lower activation energy, increasing the reaction rate.
Why do smaller solid particles increase the rate of reaction?
Smaller particles have a larger surface area, increasing the likelihood of collisions and speeding up the reaction.
Why do higher temperatures increase the rate of a reaction?
Higher temperatures give particles more kinetic energy, increasing collision frequency and energy, leading to more successful collisions.
How do concentration and pressure affect the rate of reaction?
Higher concentrations and increased pressure lead to more frequent collisions between particles, increasing the rate of reaction.
What are the four main factors that affect the rate of a reaction?
- Concentration and pressure.
- Temperature.
- Particle size of a solid.
- Presence of a catalyst.
How is the rate of a reaction defined?
It is the change in concentration of reactants or products per unit time.
How does temperature affect the rate of reaction?
Particles have more kinetic energy so collisions between particles are more frequent increasing the chance of successful collisions
How does particle size of solid affect rate of reaction?
Smaller the size the greater the surface area to volume ratio and the faster the reaction which is why powdered stuff reacts better than lumps or large chunks
How does the presence of a catalyst increase the rate of reaction?
Increases the rate of reaction by providing an alternative route and lowering activation energy without being used up itself
How does concentration and pressures affect rate of reactions?
- In solutions, increasing the concentration of reactants means there are more particles in a given volume.
This leads to more frequent collisions between reactant particles, increasing the chances of successful collisions, which speeds up the reaction.
2.Increasing the pressure of a gas compresses the particles into a smaller volume.This also increases the frequency of collisions between gas molecules, accelerating the reaction rate.
Define activation energy
The minimum energy needed by colliding molecules for them to react. For a collision to lead to a reaction, the collision energy must be equal to or greater than the activation energy.
What is the formula to calculate rate of reaction?
Rate= change in conc/ time
How does increasing concentration affect the rate of reaction?
Increasing the concentration increases the number of reactant particles in the same volume, leading to more frequent collisions, which increases the rate of reaction.
What is the effect of pressure on gaseous reactions?
Increasing the pressure reduces the volume and increases the concentration of gas molecules, leading to more collisions and a faster reaction rate.
How is the reaction between sodium thiosulfate and hydrochloric acid monitored?
The time taken for the yellow precipitate of sulfur to form is measured. A higher concentration shortens this reaction time.
What do the concentration graphs (Figures 12 & 13) indicate about reaction rates?
The reaction rate is fastest at the beginning when the reactant concentration is highest. As the reaction progresses, the rate decreases because reactants are used up.
How is the rate of reaction calculated using a concentration-time graph?
By drawing a tangent at a specific time point, the gradient of the tangent (change in concentration ÷ change in time) gives the rate of reaction at that instant.
How does temperature influence reaction rates?
Higher temperatures increase the number of particles with energy equal to or greater than the activation energy, leading to more successful collisions.
What does the Maxwell-Boltzmann distribution illustrate?
It shows how energy is distributed among particles. At higher temperatures, a greater fraction of molecules exceeds the activation energy threshold.
How does a catalyst affect a reaction?
A catalyst provides an alternative pathway with a lower activation energy, increasing the fraction of particles that can successfully react.
What is the Maxwell-Boltzmann distribution with a catalyst?
With a catalyst, the energy threshold (activation energy) is reduced, so more particles have sufficient energy to react.
Does a catalyst get used up during a reaction?
No, a catalyst is not consumed in the reaction and can be reused.
What happens to a catalyst if it becomes poisoned?
It can no longer lower the activation energy, and the reaction rate decreases.
Why does food last longer in a fridge?
Lower temperatures reduce the energy of particles, decreasing the number of successful collisions and slowing down the rate of reactions that cause food spoilage.
Why does milk sour more quickly at room temperature?
At room temperature, particles have more energy, leading to more frequent and successful collisions, increasing the rate of reactions that cause milk to sour.
