Equilibria Reactions Flashcards
Define a reversible reaction?
A reaction where the products can react to form the original reactants
Define dynamic equilibrium
A equilibrium that exists when the rate if the forward reaction is equal to the rate of the backward reaction.
What is Le Chateliers principle?
When a system in a dynamic equilibrium is changed, the position of equilibrium will shift to minimise the change.
How does increasing the temperature affect the equilibrium?
Favours the endothermic reaction so energy is taken in as the excess heat needs to be removed. Equilibrium shifts to lower the temperature and so moves to the right increasing the concentration of the products.
How does decreasing the temperature affect the equilibrium?
Favours the exothermic reaction so energy is given out as heat needs to be gained. Equilibrium shifts to raise the temperature and moves towards the right, increasing the concentration of the products.
How does increasing the pressure affect the equilibrium?
Favours the side with fewer molecules to release the build up of pressure by increasing the yield on this side of the reaction and decreasing the concentration on the other side.
How does decreasing the pressure affect the equilibrium?
Favours the side with the most molecules to increase the pressure by increasing the yield on this side of the reaction and decreasing the concentration on the other side.
How does increasing the concentration of the reactants affect the equilibrium?
Favours the forward reaction as there are more reactants available to react. Thus the concentration of products will increase to minimise the change causing equilibrium to shift to the right.
How does increasing the concentration of the products affect the equilibrium?
Favours the backward reaction as there are more products available to thermally decompose. Thus the concentration of reactants will increase to minimise the change, causing equilibrium to shift to the left.
What is Kc?
The equilibrium constant which indicates the position of euqilibrium in a reaction depending on temperature.
What is the formula for kc?
Kc= [C]^c[D]^d / [A]^a[B]^b
How does increasing the concentration of the reactants affect Kc?
Stays the same
How does increasing the pressure affect Kc?
Stays the samae
Why do catalysts not affect Kc?
A catalyst increases the rate of reaction without changing the position of equilibrium as it is not involved in the reaction.
Define a weak acid
An acid that only slightly dissociates into its ions
Define a strong acid
An acid that completely dissociates into its ions
What is pH?
A measure of acidity and alkalinity based on the concentration of H+ ions present in a solution.
What is the formula for pH?
pH= -log10 [H+]
[H+]= the concentration of the acid
How do you calculate the H+ ion concentration?
[H+]= 10^-pH
What is a bronsted-lowry acid?
An acid is a donor of protons (H+ ions)
What is a bronsted-lowry base?
An base is a acceptor of protons (H+ ions)
List the apparatus need to carry our a titration?
Burette
Conical Flask
Pipette
Funne;
Clamp Stand
White tile
How do you carry out a titration?
- use a pipette to add a measured volume (usually 25 cm3) of alkali to a conical flask.
- add a few drops of indicator to the solution in the conical flask
- run acid from the burette to the solution in the flask, swirling as you do so. Stop when the
indicator turns colour. - Record a rough value and repeat the titration, this time adding the acid dropwise when you get to a volume close to the rough value, do this until the indicator just turns colour. This is the end-point of your titration.
Record the volume of acid used (the titre). - Repeat until you have at least two readings that are within 0.20 cm3 of each other and calculate a
mean titre.
Why do you swirl the conical flask in a titration?
To ensure all particles react in the mixture
