Year 12- Kinetics (Physical Chemistry) Flashcards
What is collision theory?
Reactions can only occur when successful collisions occur between particles with activation energy.
What is activation energy?
The minimum energy which particles need to collide to start a reaction
What is the effect of increasing temperature on the maxwell-botlzmann curve?
The Emp and mean energy shift to higher energy values, but eh no. of molecules with those energies decrease.
-The curve shifts to the right, becomes shorter but the line stays above the og curve.
What is the rate of reaction?
The change in concentration of a substance in unit time. Units are mol dm-3 s-1.
How do you calculate rate of reaction from a curve?
Drawing a tangent to the curve and calculate its gradient.
When is reaction rate measured using 1/time? Explain why.
In the experiment between sodium thiosulfate and hydrochloric acid. Time is the amount taken for a cross underneath to disappear due to the cloudiness of sulfur.
-Due to concentration not being included. We assume the amount of sulfur is fixed and constant.
What is the effect of increasing concentration/ pressure on the rate of reaction?
There are more particles per unit volume so they collide with greater frequency and there will be higher frequency of successful collisions.
How does maxwell-boltzmann’s curve change with increased concentration/pressure?
The curve is raised higher as there are more particles so a greater area but the shape remains the same.
-More molecules have energy greater than the activation energy.
Effect of increasing surface area on the rate of reaction
-Causes successful collisions to be more frequent which increases rate of reaction
Effect of a catalyst on the rate of reaction
They increase the rate of reaction by providing an alternative pathway with a lowered activation energy. More particles have energy greater than the activation energy so there will be higher frequency of successful collisions.
