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Strong Acid and Strong Base
When a strong acid and a strong base are mixed, they react quantitatively in a reaction represented by the equation:
H+ (aq) + OH– (aq) → H2O (l)
pH determined by concentration of excess reagent
Weak Base-Strong Acid
If the weak base is in excess, then a buffer solution is formed, and the pH can be determined from the Henderson–Hasselbalch equation equation:
pOH = pKb + log [B]/[BH+]
If the strong acid is in excess, then the pH can be determined from the moles of excess hydronium ion and the total volume of solution
pH = -log10[H3O+]
If they are equimolar, then the (slightly acidic) pH can be determined from the equilibrium represented by the equation:
HB+ (aq) + H2O (l) ⇌ B (aq) + H3O+ (aq)
Strong Base-Weak Acid
If the weak acid is in excess, then a buffer solution is formed, and the pH can be determined from the Henderson-Hasselbalch equation
pH = pKa + log[A-]/[HA]
If the strong base is in excess, then the pH can be determined from the moles of excess hydroxide ion and the total volume of solution
If they are equimolar, then the (slightly basic) pH can be determined from the equilibrium represented by the equation:
A– (aq) + H2O (l) ⇌ HA (aq) + OH– (aq)
Weak Acid-Weak Base
In an acid base reaction, the equilibrium will favour the side with the weaker acid and weaker base
If the equilibrium constant for the reaction is greater than one (K >1) the equilibrium will favour the formation of products
This means the weaker acid and weaker base are on the product side
If the equilibrium constant for the reaction is less than one (K <1) the equilibrium will favour the formation of reactants
This means the weaker acid and weaker base are on the reactant side
