Acid-Base And pH Flashcards
What are the three definitions of acid-base?
Arrenhenius
Bronsted-Lowry
Lewis Theory
What is the Arrhenius definition for acid and base?
Acid: produces hydrogen ion and an ion in water.
Base: produces hydroxide or hydroxyl ion and a cation in water.
What is the Bronsted-Lowry definition of acid and base?
Acid: a proton donor
Base: a proton acceptor
What is the Lewis theory definition of acid and base?
Acid: accepts electrons
Base: donates electrons
What is a Brønsted-Lowry acid-base reaction?
A proton is transferred from an acid to a base.
What is an amphirotic solvent?
A solvent that can act as an acid or base. (H2O)
What are strong acids?
Powerful proton donors
What are weak bases?
Conjugated base of strong acid.
What is a strong base?
High tendency to accept protons.
What is a weak acid?
Conjugate acid of a strong base.
What value do strong acids have for Ka?
Large
What value do weak acids have for Ka?
Small
What does a smaller pKa mean?
Stronger acid
Weaker base
Large Ka
What does a larger pKa mean?
Weaker acid
Strong base
Small Ka
What is the value of pKw?
14
pKa+pKb
How do we assess acidity?
Stabilisation of a conjugate base.
The more stable the conjugate base=more acidic is the compound
How do we assess basicity?
Ability to use its nonbonding electrons to combine with a proton.
What influences acidity and basicity?
Electronegativity
Bond energy
Inductive effects
Hybridisation effect
Resonance/ Delocalisation effects
How does the increase of electronegativity influence acidity and basicity?
Increase acidity by stabilising negative charge of the conjugate base.
Decrease basicity as electrons of more electronegativity are less likely to be donated to a proton.
How does bond energy influence acidity?
Increase as its able to disperse the negative charge over the atom weakening the bond strengths.
How does inductive effect influence acidity?
Increase.
How does the hybridisation effect influence acidity and basicity?
sp,sp2 and sp3 increase acidity
sp3,sp2 and sp increase basicity