1.7 Simple equilibria and acid-base reactions Flashcards
What does the term dynamic equilibrium mean and what are characteristics of a process in this state?
Dynamic equilibrium is the equilibrium that exists when the rate of the forward reaction equals the rate of the reverse reaction.
A chemical system is in dynamic equilibrium when:
-it is dynamic at the molecular or ionic level
-both forward and reverse rates are equal
-it is a closed system, i.e. a system where substances cannot leave or enter
-it has macroscopic properties, e.g. concentration of the reactants and the products remain the same.
What does Le Chatelliers principle state?
If a system at equilibrium is subjected to change, the equilibrium tends to shift so as to minimise the effect of the change.
What happens if the conc of reactants is increased?
The position of equilibrium moves to the right and more products are formed and vice versa
What happens if the system undergoes an increase in pressure?
The position of the equilibrium will move to whichever side of the equation has fewer moles and vice versa
What happens if the system undergoes an increase in temperature?
Position of equilibrium will shift to the endothermic direction
How does a catalyst effect the equilibrium?
The position of the equilibrium will not move as a catalyst works equally with the forward and back reaction, so the equilibrium is just reached faster.
What is the expression for Kc?
aB + bB = cC + dD
[C]^c[D]^d/[A]^a[B]^b
If the value of Kc is > than 1 what does this mean?
It shows there are more products than reactants and the position of equilibrium lies to the right. The greater the value of Kc, the further the position of equilibrium is to the right.
If the value of Kc is < than 1 what does this mean?
There are more reactants than products and the position of equilibrium lies to the left. The smaller the value of Kc the further to the right.
What is the only variable that can change Kc?
temperature
What is an acid and base?
acid is [H+] donor
base is [H+] acceptor
What is the formulae of sulfuric acid?
H2SO4
What is the formulae of nitric acid?
HNO3
if a base dissolves in water what is it called?
alkali
what is a common ion found in all alkalis
OH-
what is the equation for pH?
minus log to the base 10 multiplied by the conc of H+ ions in mol dm-3
what is a salt?
a salt is the compound that forms when a metal ion replaces the hydrogen ion in an acid.
What are two examples of a primary standard?
-KHP for standardisation of bases
-Sodium carbonate for standardisation of aqueous acids
How is a primary solution prepared from a solid
what are titrations?
Titrations are a type of volumetric analysis where a solution of known concentration is reacted with a solution of unknown concentration and the reacting volumes are used to work out the unknown concentration. In an acid-base or neutralisation reaction, the equivalence point is measured using an indicator.
In order to know the exact concentration of the one solution, a standard solution must be used or one that has been standardised using a standard solution.
