Chapter 10 Flashcards
What is the minimum energy required for particles to collide and start a reaction called?
Activation Energy (EA)
Activation Energy is defined as the minimum energy which particles need to collide to start a reaction.
How does increasing concentration affect reaction rates?
Higher concentration increases the frequency of effective collisions
More particles per unit volume lead to more collisions.
What is the unit for measuring the rate of reaction?
mol dm-3 s-1
The rate of reaction is defined as the change in concentration of a substance in unit time.
How is the rate of reaction determined from a concentration vs. time graph?
The gradient of the curve
The initial rate is the rate at the start of the reaction where it is fastest.
In the experiment with sodium thiosulfate and hydrochloric acid, how is the reaction rate typically measured?
1/time
This measures the time taken for a cross to disappear due to the cloudiness of sulfur produced.
What is the effect of catalysts on reaction rates?
They increase reaction rates without being used up
Catalysts provide an alternative route with lower activation energy.
What is a heterogeneous catalyst?
A catalyst in a different phase from the reactants
Heterogeneous catalysts are usually solids while reactants are gases or in solution.
What is a homogeneous catalyst?
A catalyst in the same phase as the reactants
The reaction proceeds through an intermediate species.
What are some benefits of using catalysts?
Lower temperatures and pressures, reduced energy costs, fewer CO2 emissions
Catalysts can also improve atom economy and reduce waste.
What technique can be used to measure the change in volume of a gas during a reaction?
Using a gas syringe
This is applicable when there is a change in the number of moles of gas in the reaction.
What method can be used to quench a reaction for titration?
Dilution with water, cooling, or adding a reagent
These methods stop the reaction before titration with a suitable reagent.
How does the Maxwell-Boltzmann distribution illustrate molecular energy?
It shows the spread of energies that molecules have at a particular temperature
The area under the curve represents the total number of particles present.
What happens to the energy distribution of molecules as temperature increases?
More molecules have higher energies
The mean energy shifts to higher values, increasing the frequency of successful collisions.
How does increasing surface area affect reaction rates?
Increases the frequency of collisions
More collisions between reactant particles lead to a faster reaction.
True or False: Only a few particles have energy greater than the activation energy (EA).
True
Most molecules have energies below the EA, but reactions can still occur through collisions.
What is dynamic equilibrium?
Dynamic equilibrium occurs when forward and backward reactions are occurring at equal rates.
What does the ‘position of equilibrium’ refer to?
The composition of the equilibrium mixture.
If the position of equilibrium favors the reactants, where is it described to be?
Towards the left.
What does Le Chatelier’s principle state?
If an external condition is changed, the equilibrium will shift to oppose the change.
What effect does increasing temperature have on the position of equilibrium?
The equilibrium will shift in the endothermic direction to reduce the temperature.
What happens to the equilibrium if temperature is decreased?
The equilibrium will shift in the exothermic direction to increase the temperature.
Fill in the blank: If temperature is increased, the position of equilibrium will shift towards the ______.
left
What effect does increasing pressure have on the equilibrium?
The equilibrium will shift towards the side with fewer moles of gas.
What happens to the equilibrium if pressure is decreased?
The equilibrium will shift towards the side with more moles of gas.
