.5 Kinetics Flashcards
What factors affect rate of reaction, what is the effect and why
Concentration of a solution
Effecr: Higher conc., faster reaction (unless reagent is zero order)
Reason: Particles are closer together so more freq, succ collisions
SA of a solid
Effect: More pieces solid is broken into, greater SA (powder has largest) snd faster the reaction
Reason: More particles exposed at the surface that can be collided with, so more freq, succ collisions
P of gases (that are reactants)
Effect: Higher pressure, faster reaction (unless reagent is zero order)
Reason: Particles closer together so more freq, succ collisions
Temperature
Effect: Higher temp, faster the reaction
Reason: Particles have more energy so greater proportion of collisions are successful. Particles also move faster so collisions more frequent. Therefore there are more frequent successful collisions
Catslyst
Effect: Increases rate of reaction and not used up
Reason: Provides alt route/mechanism with lower AE and therefore greater proportion of succ collisions
How to find rate from a graph
do ones on FCs without looking at answers, and ones in kinetics booklet
Gradient at any time equals rate of reactio at that time
steeper line, faster rate
Can calc by drawing tangent to line at any point, then doing change in y over change in x
(change in conc. over change in time)
Draw a graph for Maxwell Boltzmann Curves (Temperature)
Label high temp, low temp Ea and Emp for each
What does increase/decrease in temp do to shape of graph, area below graph, particles with higher E than E a etc
The lower temp distribution is to the left and has a higher peak.
The higher temp distribution is to the right and has a smaller peak
At a higher temperature the area below the curve beyond the Ea is higher; more particles have the minimum Ea
A small increase in temperature has a significant increase in the number of molecules with enough Ea
Both curves should be asymptotic on close inspection
Draw a graph for Maxwell Boltzmann Curves (Catalyst)
Label Ea and Emp
What does catalyst do to shape of graph, area below graph, particles with higher E than E a etc
The activation energy mark should only change for a curve showing the addition of a catalyst
However, the distribution would remain unchanged.
No change in shape of graph
White phosphorus will spontaneously burn in air to make phosphorus oxide. Comment on the activation energy for this reaction. Explain your reasoning.
The reaction of white phosphorus with oxygen has a very low activation energy, so that molecules at room temperature have enough energy to react.
The production of ammonia depends on reacting gaseous nitrogen and gaseous hydrogen. How does high pressure increase the reaction rate?
High pressure means there are more molecules in
the same volume (than at a low pressure), so the molecules are closer together. The number of collisions increases, so the reaction rate increases. (This is similar to changing the concentration.)
