AS - Kinetics Flashcards
What is reaction rate defined as?
The change in concentration of a reactant or product over time.
Give the formula for finding the rate of a chemical reaction.
Rate of reaction = amount of reactant used or product formed divided by time
Particles don’t react every time they collide. When and only when will a reaction take place between two particles?
- The particles collide in the right orientation.
2. The particles collide with at least a certain minimum amount of kinetic energy (the activation energy).
What is activation energy?
The minimum amount of energy that particles need to react.
Do all molecules in a gas have the same amount of energy? Explain this.
No, some molecules have less kinetic energy and move slowly, some have lots of kinetic energy and move fast. Most molecules are somewhere in between.
What are the axes on a Maxwell-Boltzmann Distribution graph?
Y-axis = number of molecules
X-axis = kinetic energy
Why does the Maxwell-Boltzmann curve start at 0,0?
Because no molecules have zero energy.
What is the area under a Maxwell-Boltzmann distribution curve equal to?
The total number of molecules.
What does the peak of the MB curve represent?
The most likely energy of any single molecule.
Where is the mean energy of all the molecules found on the MB curve?
A little to the right of the peak.
Which are the only molecules in a gas to react?
Those with the same amount or more than the activation energy.
Why does a small increase in temperature lead to a large increase in rate if reaction?
If you increase temperature, the particles on average will have more kinetic energy and so will move faster. Therefore a greater proportion of molecules will have at least the activation energy and be able to react.
And because molecules are moving faster, they’ll collide more often.
Both of these effects happening at once (more collisions and more energetic collisions) means that small increases in temperature can lead to large increase in rates of reaction.
How does an increase in temperature affect the MB curve?
The peak is lower and moves to the right, and the activation energy increases. The line at the end of the curve is slightly higher than the previous curve.
How does increasing the concentration of reactants of a reaction change the rate of reaction and why?
Rate is increased because when you increase concentration, particles on average will be closer together and therefore collide more often. If collisions occur more frequently, particles will have more chance to react.
How does increasing pressure affect the rate of a gas reaction and why?
Rate increases because the gas particles are on average, closer together making them more likely to collide. Therefore collisions take place more frequently and rate increases.
