Section 5 - Kinetics, Equilibria and Redox Reactions Flashcards
(70 cards)
Define reaction rate
Change in concentration/amount of a reactant or product over time.
What is the formula for rate of reaction?
Amount of R used or P formed/time
What are the two conditions that allow a reaction to take place when particles collide?
- right direction - activation energy
Define activation energy
Minimum amount of kinetic energy required for particles to react upon collision.
What does a Maxwell-Boltzmann distribution show?
The number of molecules in a gas against their kinetic energy.
What is the area under a Maxwell-Boltzmann distribution?
The total number of molecules.
Why does a Maxwell-Boltzmann curve start at (0,0)?
0 molecules will have 0 energy
What does the peak of the Maxwell-Boltzmann curve show?
The most probable energy of any molecule.
Where is the mean energy of all of the molecules in a Maxwell-Boltzmann curve?
Slightly to the right of the peak.
Where would you find the section of molecules with the required activation energy on a Maxwell-Boltzmann curve?
On the right.
What happens to the average kinetic energy if the temperature of a reaction is increased?
It will increase.
What happens to the proportion of molecules with the required activation energy if the temperature of a reaction is increased?
It will increase.
How does the Maxwell-Boltzmann curve change when temp is increased?
- shifts to right - peak is smaller
Why does rate of reaction increase with temp?
- molecules have more energy - more have Ea required - move faster - collide more often - more likely to react
Why does rate of reaction increase with concentration?
- particles closer together - collide more often - more likely to react
Why does rate of reaction increase with pressure?
- particles closer together - collide more often - more likely to react
Why does rate of reaction increase with a catalyst?
- provide alternative route with lower Ea - more particles have enough energy to react - more likely to react
Define catalyst
A substance that increases the rate of a reaction by providing an alternative reaction pathway with a lower Ea. It is chemically unchanged at the end of the reaction.
Why are catalysts good in industry?
- don’t get used up (small amount required) - work faster - allow a lower temp
Give 3 ways to measure reaction rates:
1) Timing how long a precipitate takes to form 2) Measure a change in mass 3) Measure vol of gas given off
Give a negative of timing how long a precipitate takes to form
Subjective
Give a pro and con of measuring a change in mass
+ accurate and easy - releases gas
Give a pro and con of measuring vol of gas given off
+ accurate - only works if one or more product is gaseous
Give an example of a reaction that forms a precipitate
Sodium Thiosulfate and Hydrochloric Acid
