6.2 Using Brønsted-Lowry Theory Flashcards
when and what was Svante Arrhenius’ theory?
- acids produced H+ ions in water, bases produced OH+ ions in water
3 limitations of Arrhenius’ theory
(1) there were exceptions
(2) doesn’t account for solvents other than water
(3) doesn’t account for states other than aqueous
when and what was Bronsted-Lowry’s theory
- acids are proton donors, and bases are proton acceptors (concept of conjugate acid-base pairs)
importance of BL theory (3)
(1) shows acidity depends on properties relative to other substances present in reaction, not just on structure
(2) neutralisation didn’t need to involve ionisation to H+ but just proton transfer
(3) hydrolysis of salts to produce pH was separate from acid-base reactions
2 limitations of BL theory
doesn’t explain acidity of acidic oxides (which has no proton transfer)
doesn’t account for acids that don’t have hydrogen
amphiprotic vs amphoteric substance
amphiprotic substances that can both donate and accept protons (weak acid/base) depending on what they react with (doesn’t need to involve hydrogen)
amphoteric substances react as either acids or bases (usually involves hydrogen)
how to recognise BL conjugate acid-base pairs
acid –> base (donated proton)
base –> acid (accepted proton)
weak acid has a … base pair, and vice versa
strong
3 common amphiprotic substances
HPO4 -2
HCO3 -
HSO4 -
two common ways to write equations that identify amphiprotic substances
reaction with HCl and OH-
OR
reactions with H2O
the single arrow is for …
the double arrow is for …
single arrow for strong acid/base
double arrow for weak acid/base
most naturally occurring acids are organic that contains ___ group
COOH (carboxyl)
equilibrium of strong acid equation
right (ionises completely)
equilibrium of weak acid equation
left (majority still molecules)
polyprotic acids…
have more than 2 dissociable protons that undergo stepwise ionisation
multiple hydrogen ions in the acid
