Kinetics Flashcards
(26 cards)
What is collision theory?
For particles to react they must collide with sufficient energy and at the correct orientation
What is activation energy?
The minimum energy particles need to react
What are the 5 factors that affect the rate of a chemical reaction?
- Temperature
- Surface area
- Pressure
- Concentration
- Use of a catalyst
How do you calculate the rate of a reaction?
rate of reaction = amount of reactant used or product formed / time
Define the rate of a reaction?
The change in concentration of a reactant or product per unit time
What are the features of the maxwell-boltzmann curve?
- The particles in a substance don’t all have the same amount of energy
- The area under the curve represents the total number of particles
- The peak of the curve (Emp - most probably energy) gives the energy that more particles have than any other energy
- Ea represents the activation energy and only a small proportion of molecules have energy greater than or equal to the activation energy
Draw a maxwell-boltzmann curve when the temperature increases
Well done
How does concentration affect the rate of a reaction?
The higher the concentration, the faster the reaction because the particles are closer together and so there are more frequent successful collisions
How does pressure affect the rate of a reaction?
The higher the pressure, the faster the reaction because the particles are closer together and so there are more frequent successful collisions
How does temperature affect the rate of a reaction?
The higher the temperature, the faster the reaction because the particles have more energy and they move faster so there are more frequent successful collisions
How does surface area affect the rate of a reaction?
The greater the surface area, the faster the reaction because there are more particles exposed at the surface so there are more frequent successful collisions
How does a catalyst affect the rate of a reaction?
A catalyst increases the rate of a reaction as it provides an alternative route with a lower activation energy so a greater proportion of the collisions are successful
What are the necessary conditions for equilibria?
- A closed system
- Reactants and products are present at all times
- Forward and reverse reaction occur at the same rate (dynamic reaction)
- Concentration of reactants and products remain constant
What is a closed system?
When nothing can get in or out
What happens at dynamic equilibrium?
When both the forward and the reverse reactions take place simultaneously and at the same rate
What is Le Chatelier’s principle?
If the conditions of a reaction at equilibrium are changed, then the position of the equilibrium moves to oppose that change
What is the effect of a catalyst on equilibrium?
It increases the rate of the forwards and backwards reactions equally and it doesn’t change the position of equilibrium but it reaches equilibrium faster
What effect does high temperature have on the position of equilibrium?
An increase in temperature means it shifts in the endothermic direction to oppose the change
What effect does high pressure have on the position of equilibrium?
An increase in pressure means that it shifts in the direction with fewer gas molecules to oppose the change
What effect does increased concentration have on the position of equilibrium?
It shifts in the direction to use up the added substance
What are the conditions used for the haber process and why?
- Temperature of 450°C is used as a lower temperature will give a higher yield because the reaction is exothermic. However a lower temperature would cause the reaction to take too long
- Pressure of 200atm as a higher pressure gives a higher yield of ammonia. However, too high of a pressure would be very expensive to maintain
- An iron catalyst is used to increase the rate of reaction
What is the equation for the equilibrium constant?
Kc = products / reactants
What is the equilibrium constant affected by?
Temperature
What does the value of the equilibrium constant depend on?
The position of equilibrium
