ES - Rates And Equilibris Flashcards
Explain why increasing the concentration of H2O2 increases the rate of reaction
More crowded particles
More frequent collisions
Explain why increasing the temperature of of H2O2 increases the rate of decomposition
(Use a Boltzmann distribution)
More molecules have energy above activation energy
Explain why Hugh pressures ad low temperatures would gibe the maximum equilibrium yield of methanol
High pressure because fewer moles of gas on the RHS
Low temp because it shifts the reaction in the direction of the exothermic
And forward reaction is exothermic
Which way is equilibrium shifted if temp is increased?
In the direction of the endothermic reaction (yielding more reactants)
How to tell if forward reaction is exothermic
H is negative
Explain why the actual conditions used in the chemical industry might be different from high pressure and low temp
High pressures are too expensive
Too slow to use a low temperature
Suggest 2 ways in which the use of catalysts helps chemical companies to make their processes more sustainable
Catalysts are not used up in reaction
Reactions take place at lower temperatures
State Le Chatelier’s principle
When the conditions on a system in equilibrium are changed
the equilibrium moves to oppose the change
What would happen to equilibrium if temp is increased
Move towards LHS
As reverse reaction is endothermic
What happens to equilibrium if catalyst is added?
Nothing would change
Catalyst;lists speed up forward & reverse reactions by the same amount
Explain how an increase in temp causes the rate of reaction to increase
Area under Fira-h exceeding Ea = number of molecules that can react
At higher temp the area under the curve greater than Ea is bigger
So more can react
Use collision theory to explain the changes in the rate fop reactions as they proceed
- The concentration decreases
- Collisions decrease
- Reaction stops when all of one reagent is used up
State and explain what effect using a weaker acid has on the rate of reaction
Rate of reaction decreases
Lower concentration of H+ in weak HCl
3 features of a reversible reaction
- closed system
- concentrations remain constant
- rate of forward reaction = rate of reverse reaction
What is meant by a catalyst?
A substance that lowers activation energy by providing an alternative route
What is meant by homogeneous?
Catalysts in the same state as the reactants
Using the fact that acids are needed to catalyse this reaction, deduce the formula of the ion that acts as the catalyst
H+
Catalyst do not affect the position of an equilibrium. Explain why not
They alter the rate of the forward and reverse reaction by the same amount
What goes on the Y axis of Boltzmann?
Number of molecules/particles
Explain the effects of catalysts on the rate of reaction (with reference to the graph)
Greater proportion of collisions have greater than Ea
Pressure for Haber process
50-1000 atm
Temperature for Haber process
200-600 degrees Celsius
Explain why the Haber process is a compromise between rate and equilibrium
Compromise as
If temp is too high, low yield
If temp it too low, slow rate
If pressure is too high, increases cost
State and explain the effect on an equilibrium of a decrease in pressure
Decrease as particles are further apart
So there are less frequent collisions
The forward reaction is exothermic. Explain how the graph supports this statement
As temp increases, conversions are decreasing
Equilibrium gas moved to LHS (endothermic direction)
Suggest 2 reasons why it us necessarily to heat the calcium carbonate strongly to achieve decomposition
- To overcome activation energy
- Reaction is endothermic
State and explain what happens to the composition of the mixture in the container when CO2 escapes
Moves to RHS
Le chatelier’s principle
Causes more products (compensation)
Suggest why the conversion was such less than the theory suggested
Other products were formed
Give two economically important processes that use catalyst and state their catalysts
Haber process - iron
Catalytic cracking - platinum
What affect does a catalyst have on the rate of a reaction and how does it achieve this affect? (4)
Increases rate
By providing alternative route
Which decreases activation energy
By weakening bonds in the reactant
So more molecules have E > Ea
