Topic 7 - Equilibria Flashcards
What makes a state of equilibria dynamic?
The rate of the forward reaction is is the same as the rate backward reaction in a a closed system and the concentrations of the reactions and product is constant
state
Le Chateliers principle
If a condition that affects the position of equilibrium of a system is altered, the position of equilibrium will shift to counteract the effect of the change
What changes can affect position of equilibrium?
Additional or removal of products or reactants
Change in pressure
Change in temperature
Effects of pressure
Is pressure is increased the position of equilibrium will shift to the side that has less gas’s molecules to try reduce the pressure
Effect of Temperature
If temperature goes up the pos of equilibrium will shift to favour the endothermic reaction vice versa
Equation
Constant of concentration
Reactant concentration ^ reactant mol / product concentration ^ product mole
Kc is temperature specific
Solids don’t count
Units are not fixed
equation
Constant of pressure
Partial pressures of products ^ mol /
Partial pressures of reactants ^ mol
equation
Partial pressures
Total pressure * mol fraction
What is an Acid?
Proton donor ; species that gives away a H+
What is a Base ?
Proton acceptor; species that receives a H+
What is the difference between a strong or weak acid or base
Strong - dissociates almost completely in aqueous solutions
Weak - partial dissociation in aqueous solutions
Examples of strong acids?
HCI H2SO4 HNO3
Example of weak acids?
CH3COOH HCN H2S H2CO3
Example of strong bases ?
Group one metal hydroxides
Example of weak bases ?
NH3 amines, hydroxides of transition metals
How to differentiate between strong bases and acids and weak ones?
pH
Neutralisation enthalpy
Electrical conductivity
Rates of reaction
What makes an acid strong?
If it’s anion is more stable, an acid is stronger as H+ ions can dissociate more as there is no need for the two to bond again
How is Neutralisation Enthalpy?
-57 kj/mol strong acid strong base
If a weak acid is neutralised energy is needed to dissociate the molecules the value is lower than 57 (numerically lower)
How does conductivity vary between strong and weak acids/bases?
Stronger acids and bases have more ions that can carry more current at the same voltage and concentration
Reaction Rate
The stronger the acid (higher concentration of ions) the faster the rate of reactions
Can be measured by effervescence, volume of gas per unit time
