9 kinetics 1 Flashcards
What is chemical kinetics?
The study of chemical reactions
What is the equation for rate of reaction?
Change recorded in property/time for the change.
In a reaction between magnesium and hydrochloride acid, what are the ways to measure rate of reaction?
- the rate of loss of magnesium
- the rate of loss of hcl
- the rate of formation of mgcl
- the rate of formation of hydrogen
How can rate of reaction be measured on a graph of conc against time?
Taking the gradient at a given time will give the rate at that point.
How does concentration affect rate of reaction?
The higher the conc of reactants the faster the rate
- for gas reactions an increase pressure also has the same affect as increasing conc.
How does the surface area of a solid affect the rate of a reaction?
Breaking solid into smaller pieces increases total surface in contact with the liquid or gas.
This speeds up the rate of reaction.
This principle is also the same for immiscible liquids
How does temp affect rate of reaction? Why?
Increasing temp, increases rate of reaction.
This is due to molecules having more kinetic energy and colliding at faster rates and much more frequently. Therefore more molecules have the required activation energy for a reaction to occur upon collision
How do catalysts affect rate of reaction?
They speed up the rate of reaction by providing an alternate pathway with a lower activation energy.
The catalyst itself is not used up in the chemical reaction.
What is a phase?
A phase is one of three states of solid, liquid or gas.
Chemical systems often have more than one phase.
What is a heterogenous catalyst?
One that is in a different phase from the reactants.
What does the maxwell Boltzmann distribution do?
Helps explain the effects of temperature and catalyst on the rate of reaction.
What does maxwell Boltzmann curve show?
It shows the spread of molecular kinetic energies for a gas at a particular temp.
It shows that there is a wide spread of molecular energies and so the molecules are moving at different speeds.
What does the area under the curve of the maxwell Boltzmann curve show?
The total number of molecules.
In a maxwell boltzmann what effect does changing the temp have to the area under the curve?
No effect as the total number of molecules remains the same
What is activation energy (Ea)?
The minimum energy required for a reaction to happen
What is a transition state?
The state of reacting atoms, molecules or ions when they are at the top of the activation energy barrier for a reaction step.
What is a reaction profile?
A graph which shows how the total enthalpy of the atoms, molecules or ions changes during the progress of a reaction from reactants to products
What is an intermediate?
Atoms, molecules or ions which dont appear in the balanced equation but which are formed in one step of the reaction then used up in another
