Chapter 10 Flashcards
Periodic Table and Energy (Reaction Rates and Equilibria)
Define the term “Rate of reaction”
Change in concentration of a reactant or product over time
Explain how increasing temperatures affects the rate of a reaction
- Increases the average kinetic energy of particles
- More particles have energy greater than or equal to the activation energy
- More frequent successful collisions
State two ways to experimentally determine the rate of a reaction
- Measuring the change in volume of gas produced over time
- Measuring the change in mass of reactants over time
- Measuring the change in concentration of a reactant or product using titration, colorimetry or conductivity
Define activation Energy
The minimum energy required for a reaction to occur
Explain the role of a catalyst in a chemical reaction
- Provides an alternative reaction pathway with a lower activation energy
- Increases the rate of reaction without being used up
What are the different types of catalyst
Homogeneous catalyst : same phase as the reactant
Heterogeneous catalyst: different phase from the reactants
Why do we use catalysts?
Catalysts have economic and sustainability benefits, as reactions can be carried out at lower temperatures than uncatalysed reactions, reducing the demand for fossil fuels and reduction emissions
Define the term “Dynamic equilibrium”
The rate of the forward reaction is equal to the rate of the reverse reaction. Concentrations of reactants and products do not change. ( Must be a closed system)
State Le Chatelier’s principle
When the system at equilibrium is subject to a change, the equilibrium position will shift to counteract the change.
How does increasing the pressure affect the equilibrium position in a gaseous reaction?
Shifts the equilibrium towards the side with fewer moles of gas
How does increasing temperature affect the equilibrium position in an exothermic reaction?
Shifts the equilibrium towards the more endothermic side (reactants= left)
Write the equilibrium constant expression Kc
Kc = ( Product)^n / (Reactant)^n * (Reactant)^n
What does Kc tell us about the position of the equilibrium?
Kc>1 Equilibrium lies to the right
Kc<1 Equilibrium lies to the left
How toes a catalyst affect the position of equilibrium?
A catalyst does not affect the position of equilibrium. it speeds up both the forward and the reverse reaction equally, so the equilibrium is reached quicker
Explain how you would determine the value of Kc experimentally
- Allow the reaction to reach equilibrium
- measure the equilibrium concentrations of all reactants and products
- substitute the values into the Kc expression
