Physical Chemistry Flashcards
Equilibrium
When the composition of the reactants and products remain constant and the rate of the forward reaction equals that of the reverse reaction.
What is the equilibrium constant and what is its unit
K it doesn’t have units
What happens when temperate is increased
The equilibrium will shift towards the products If the reaction is endothermic thus increasing the K value
What happens when temperature is decreased
When temperature is decreased in an endothermic reaction the equilibrium shifts towards the reactants this causing the k value to lower
What effect does a catalyst have on the equilibrium constant
No effect.
The ionisation of water equation
H2O(l) + H2O(l) -> H30+(aq) + OH-(aq)
What is the H3O+ ion called
The hydronium ion, a hydrated proton
What does amphoteric mean and why is this quality applied to water
Amphoteric means can act as an acid or a base
What represents the disassociation constant of water
Kw=[H3O+][OH-]
How can pH be calculated
pH= -log10[H3O+]
Brønsted Lowry definition of an acid
A proton donor
Brønsted Lowry definition of a base
A proton acceptor
Why acids and bases are completed disassociated in solution
Strong acids and strong bases
Which acids and bases are only partially disassociated in solution
Weak acids and weak bases
Examples of strong acids
Hydrochloride acid, sulfuric acid, nitric acid.
Examples of weak acids
Carbonic acid, sulfurous acid, ethanoic acid.
What are strong bases
Solutions of metal hydroxides
Examples of weak bases
Ammonia and amines
How to calculate the pH of acids
pKa=-log10Ka
How to Calculate pH of weak acid
pH= 1/2pKa-1/2log10C
What does a strong acid and strong base produce
A neutral salt
What does a weak acid and a strong base produce
Alkaline salt
What does a strong acid and a weak base produced
Acidic salt
Buffer solution
A solution in which the pH remains approximately constant when small amounts of acid and base or water are added.
How is an acidic buffer made
A weak acid And it’s salt
How do acidic buffers work
The weak acid provides hydrogen ions when these are removed by the addition of a small amount of base. The salt of the weak acid provides the conjugate base which can absorb excess hydrogen ions produced on the addition of a small amount of ache
How is a basic buffer made
A weak base and its salt
How do basic buffers work
The weak base removes excess hydrogen ions when acid is added and the conjugate acid provides by the salt supplies hydrogen ions when bases are added.
How is pH of a buffer be calculated
pH= pKa-log10[acid]/[salt]
What is an indicator
A weak acid in which the disassociation constant can be represented as
HIn(aq) + H2O(l) -> H3O+(aq) + In-(aq)
How is the color of an indicator determined
By the ratio of HIn to In-
When does the color change occur in an indicator
When H3O+=KIn
Enthalpy of formation
The enthrall change when one mole of a substance is formed from its elements in their standard state
Standard state
Pressure of 1 atmosphere and temperature of 298 Kelvin
Entropy
The measure of the degree of disorder in a system
What type of entropy do solids have
Low entropy
What type of entropy do gases have
High degree of entropy
What happens to entropy when temperature increases
Entropy increases
1st law of thermodynamics
Energy cannot be created nor destroyed so the entropy of the universe is constant
2nd law of thermodynamics
States that the total entropy of a reaction system and its surroundings always increases for a spontaneous process
What happens to entropy when heat energy is released into surroundings
The entropy of the surroundings increase
What happens when heat energy is released from surrounding
The entropy of surroundings decrease
Third law of thermodynamics
The entropy of a perfect crystal at 0K is zero
What happens when the free energy between reactants and products is negative
The reaction is said to be feasible
What happens when the free energy difference between reactants and products are positive
the reaction is not feasible
What does free energy equal at equilibrium
^G=0
