9.6 Chemical Reaction Rates and Energetics Flashcards
What is a successful collision? [2]
Particles must collide with enough energy for a chemical reaction to happen.
What is activation energy? [2]
Minimum amount of energy needed for a reaction to happen
What is the symbol for activation energy? [1]
Ea
What is the rate of reaction? [2]
- How fast the reaction goes
- How often there are successful collisions
What two things does the rate of reaction depend on? [2]
- the frequency of collisions
- the energy of the collision
What things (factors) affect the rate of reaction? [5]
- concentration
- surface area
- temperature
- pressure
- catalysts
What is a catalyst? [2]
Increases the rate of reaction and is unchanged at the end of a reaction
What are practical ways to investigate the rate of reaction? [3]
- change in mass of reactant
- change in mass of product
- formation of a gas
How is the rate of reaction increased if there’s a larger number of particles or if there’s an increase in pressure? [1]
more collisions
How is the rate of reaction increased if the surface area is increased? [1]
more space for a reaction
How is the rate of reaction increased if the temperature is increased? [1]
particles have more kinetic energy
How is the rate of reaction increased if there’s a catalyst? [1]
provides an alternate route to products from reactants (lower activation energy)
Do the reactants or the products have more energy? [1]
products
Where is the activation energy always between? [2]
reactants and the peak
Where is the overall energy change always between? [2]
reactants and products
What do reactants need to make products? [1]
additional energy from around them
What is an exothermic reaction? [3]
It transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings
What is an endothermic reaction? [3]
It takes in thermal energy from the surroundings leading to a decrease in the temperature of the surroundings
What is the transfer of thermal energy during a reaction called? [1]
enthalpy change, ΔH, of the reaction
What is ΔH like for exothermic reactions? [1]
negative
What is ΔH like for endothermic reactions? [1]
positive
What is ΔH? [1]
overall energy change of the reaction
Which reactions are exothermic? [2]
- neutralisation
- displacement
Which reactions can be endothermic? [2]
- salt dissolving
- precipitation
Why is there a negative sign in exothermic reactions? [3]
- exothermic reactions give out energy to their surroundings
- temperature rise
- negative sign shows that energy is given out
Why is there a positive sign in endothermic reactions? [3]
- endothermic reactions take in energy from their surroundings
- temperature drop
- positive sign shows that energy is taken in
How do you know if a reaction if endo or exothermic in terms of bond breaking and bond making? [4]
- if the energy taken in to break bonds is GREATER than the energy released in making bonds = ENDOTHERMIC
- if the energy taken in to break bonds is LESS than the energy released in making bonds = EXOTHERMIC
What should you measure to find the rate of reaction, in general? [2]
- amount of reactant used up per unit of time
- amount of product made per unit of time
How does the speed of the rate of reaction affect the curve on a graph? [2]
- the faster the rate of reaction = STEEPER curve
- the slower the rate of reaction = SHALLOWER curve
In exothermic reactions do the reactants have more or less energy than the products? [1]
more
In endothermic reactions do the reactants have more or less energy than the products? [1]
less
Between which two points does bond breaking occur? [1]
reactants and peak
Between which two points does bond making occur? [1]
peak and products
Between which two points is energy released or taken in? [1]
reactants and products
