3.1.12 Acids and bases Flashcards
Brønsted Lowry acid definition
Proton donor
Brønsted Lowry base definition
Proton acceptor
Strong acid definition
An acid that fully dissociates in water to form H+ ions
Weak acid definition
An acid that only partially dissociates in water to form H+ ions
What does an acid base equilibria involve
The transfer of protons
Why is the pH scale sued to measure hydrogen ion concentration
It has a very wide range
pH equation
pH = -log10[H+]
Kw equation
Kw = [H+] [OH-]
Explain why [H2O] is not shown in the Kw expression
H2O is almost constant and is factored into the Kw
Explain why the value of Kw increases as the temperature increases
H2O(I) ⇌ H+(aq) + OH–
Equilibrium is endothermic
Equilibrium shifts to RHS to oppose increase in temperature
Explain why water is neutral at all temperatures despite having a different Kw value
[H+] = [OH-]
What is Ka
The dissociation constant for a weak acid
pKa equation
pKa = -log10Ka
Ka equation
([H+] [A-]) ÷ [HA]
Equivalence point
When the amount of titrant added is just enough to neutralize the solution
Half equivalence point
The half-equivalence point is the point in a titration where exactly half of the titrant has reacted with the solution. This corresponds to half the volume of the titrant needed to reach the equivalence point.
Why is pH = pKa in weak acids
The concentrations of the weak acid (HA) and its conjugate base (A-) are equal
What do buffers do
Maintain pH
Basic buffer
A weak base and a salt of that base
Acidic buffer
An acidic base and a salt of that acid
Suggest why the pH probe is washed with distilled water between each of the calibration measurements.
Different solutions must not contaminate each other
or
To wash off any residual solution/substance
