1.7 Simple equilibria and acid-base reactions Flashcards
What does it mean if a reaction is reversable?
As reactants form products, products change back into reactants at the same time - indicated by the ⇋ sign.
What can be said about a reversable reaction?
if it is endothermic in one direction, it must be exothermic in the other direction.
What is dynamic equilibrium?
Dynamic equilibrium is the equilibrium that exists when the rate of the forward reaction equals the rate of the reverse reaction.
What can be seen when a reaction is in dynamic equilibrium?
there is no observable change, nothing appears to be happening
What does the term ‘position of equilibrium’ describe?
The equilibrium state attained under a particular set of conditions.
Where does the position of equilibrium lie when there are more reactants than products?
To the left
Where does the position of equilibrium lie when there are more products than reactants?
The the right
What is Le Chatelier’s principle?
When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change.
What effect does increasing the concentration of the reactant have on the position of equilibrium?
Position moves to the RHS forming more products
What effect does increasing the concentration of the products have on the position of equilibrium?
Position moves to the LHS forming more reactants
What effect does increasing the pressure have on the position of equilibrium?
Fewer gaseous molecules on the RHS = position moves to the RHS
Fewer gaseous molecules on the LHS = position moves to the LHS
What effect does decreasing the pressure have on the position of equilibrium?
Fewer gaseous molecules on the RHS = position moves to the LHS
Fewer gaseous molecules on the LHS = position moves to the RHS
What effect does adding a catalyst have on the position of equilibrium?
A catalyst has no effect on the position of the equilibrium. It does, however, allow the state of equilibrium to be established more quickly.
What effect does increasing the temperature have on the position of equilibrium?
Endothermic forward reaction = position moves to RHS
Exothermic forward reaction = position moves to LHS
What effect does decreasing the temperature have on the position of equilibrium?
Endothermic forward reaction = position moves to LHS
Exothermic forward reaction = position moves to RHS
What expression applies when a reaction is in equilibrium?
Kc= [C(aq)]^p [D(aq)]^q / [A(aq)]^m [B(aq)]^n
According to the Brønsted-Lowry (B-L) definition, what is the definition of an acid?
Acid: donates a proton during chemical reactions
According to the Brønsted-Lowry (B-L) definition, what is the definition of an alkali/base?
Base: accepts a proton during chemical reactions; a base is called an alkali if it dissolves in water
What equation gives the pH of an acid?
pH = -log10 [H+(aq)] (with H+ being the concentration of the acid)
What equation gives the pH of an alkali?
pH = 14 – (-log10 [OH-]) (with OH- being the concentration of the alkali)
What is a titration?
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.
What is a back titration?
- Acid reacts with indigestion tablets to determine calcium carbonate percentage.
- Unreacted acid is titrated with a base to determine acid usage.
- This results in the determination of calcium carbonate content in the tablets.
What is a double titration?
- Uses indicator color changes at different pH values.
- Calculates concentrations of two bases in a solution.
- Performs in two stages using two different indicators.
- First indicator added, second added at second stage.
