State the possible outcomes if a reaction is too slow or too fast.
If the rate is too low then the process will not be economically viable; if it is too high there will be a risk of explosion.
State the 4 ways to increase the rate of a chemical reaction.
(1) by increasing the temperature (2) by increasing the concentration of a reactant (3) by increasing surface area/decreasing particle size (4) through the use of a catalyst.
Using collision theory, describe how changing the temperature increases the reaction rate.
Increasing temperature, particles have more kinetic energy, move faster, more collisions, faster rate of reaction.
Using collision theory, describe how changing the concentration increases the reaction rate.
Increasing concentration, more particles in the same volume, more collisions, faster rate of reaction.
Using collision theory, describe how changing the particle size increases the reaction rate
Decreasing particle size, increases the surface area available for reactions, more collisions, faster rate of reaction.
For a reaction to occur, what are the two conditions that must be met between the reactant molecules.
The reactants must meet with the correct collision geometry/orientation and with enough kinetic energy to overcome the activation energy
State the definition of a catalyst.
Catalysts are substances that speed up chemical reactions but can be recovered chemically unchanged at the end of the reaction.
State the symbol for a change in quantity
∆Q
State the units for the average rate of reaction if you are measuring a change in mass.
g s-1 (grams per second). Rate of reaction is 1/time
State the units for the average rate of reaction if you are measuring a change in volume.
cm3 s-1 (centimetres cubed per second)
Explain the difference between average rate of reaction and relative rate of reaction.
(1) Average rate of reaction is the rate of reaction measured over a period of time. (2) Relative rate of reaction is the rate of reaction at an instantaneous point in time
On a potential energy diagram, describe how to calculate the enthalpy change, ∆H.
The enthalpy change is the energy difference between the products and the reactants.
On a potential energy diagram, describe how you know if a reaction is exothermic.
The enthalpy change has a negative value for exothermic reactions
On a potential energy diagram, describe how you know if a reaction is endothermic.
The enthalpy change has a positive value for endothermic reactions
In a potential energy diagram, describe what the activation energy is.
The activation energy is the minimum energy required by colliding particles to form an activated complex
On a potential energy diagram, describe how to calculate the activation energy.
The difference in energy between the reactants and activated complex for forward reaction and difference between activated complex and products for reverse reaction.
In a potential energy diagram, describe what the activated complex is.
The activated complex is an unstable arrangement of atoms for,ed at the maximum potential energy barrier during a reaction.
Describe what temperature is a measure of.
Temperature is a measure of the average kinetic energy of the particles in a substance.
On a potential energy diagram, describe where the activated complex is found
It is found at the maximum of the potential energy barrier, during a reaction (the top of the curve).
On a potential energy diagram, describe what effect a catalyst would have.
A catalyst provides an alternative reaction pathway with a lower activation energy.
On a kinetic energy diagram, describe what effect a change in temperature would have.
The activation energy remains the same but the curve sifts to the right and it lowered in height. More particles have the minimum energy to react.
On a kinetic energy diagram, describe what effect the addition of a catalyst would have.
The curve remains the same but the activation energy is lowered and the line shifted to the left.
