Unit 1 - Reaction Rates Flashcards
Why does the reaction get slower as it proceeds?
The reactants are being used up
How is relative rate calculated?
Rate = 1/time
What effect does increasing concentration have on a reaction rate?
It will increase
Why does increasing concentration increase the reaction rate?
There will be more reactant molecules & more collisions
What effect does decreasing particle size have on reaction rate?
It increases reaction rate
Why does decreasing particle size increase the reaction rate?
It increases the surface area meaning more reactant particles are able to collide
What will a 10 degree rise In temperature do to reaction rate?
Roughly double it
What is activation energy?
The minimum kinetic energy required by colliding molecules for a reaction to take place
What effect does increasing temperature have on reaction rate?
It increases reaction rate
Why does increasing temperature increase the reaction rate?
It increases the number of molecules which possess the necessary activation energy to react
What is a catalyst?
A catalyst is a substance which speeds up a chemical reaction without being used up in the reaction
How does a catalyst work?
It provides an alternative pathway with a lower activation energy
What is a homogeneous catalyst?
A catalyst which is in the same physical state as the reactants
What is a heterogeneous catalyst?
A catalyst which is in a different physical state to the reactants
Where does catalysis occur?
Active sites on the surface of the catalyst
What are the three stages of how a surface catalyst works?
Adsorption
Reaction
Desorption
What is a catalyst poison?
A substance which reacts with the surface of the catalyst so that it operates less effectively or not at all
How does a catalyst poison work?
By occupying the active sites the poison stops the reactants occupying these sites
Example of a catalyst poison?
Lead in leaded petrol poisoning the catalyst in catalytic converter
Two examples of a catalyst?
Haber process - iron
Ostwald process - platinum
How is average rate measured?
Reaction rate = change in variable/time
What is an exothermic reaction?
A reaction in which energy is given out
What is an endothermic reaction?
A reaction in which energy is taken in from the surroundings
What is the activated complex?
An unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction
What is the enthalpy of combustion?
The enthalpy of combustion is the amount of energy given out when 1 mole of a substance is completely burned in oxygen
What is the enthalpy of solution?
The enthalpy of solution is the amount of energy given out or taken in when one mole of a substance dissolves in water
What is the enthalpy of neutralisation?
The amount of energy given out per mole of water formed in a neutralisation reaction
What is the relative rate?
The rate at any one particular point in time
Give 2 reasons it is important to control the rate of a reaction
Make the processes economically viable and safe.
What is the collision theory?
For a chemical reaction to take place the reactant molecules must collide with enough energy and at the correct collision geometry.
List 4 ways to increase the rate of a reaction
increase temperature
increase concentration
decrease particle size
use a catalyst
what is enthalpy?
a measure of the energy stored in a chemical
