Acids And Bases Flashcards
According to Arrhenius what is an acid
Substance that dissociates in water to produce H+ ions
According to Brønsted-Lowry what is an acid?
A proton donor
According to Arrhenius what is a base?
Substance that dissociates in water to produce OH- ions
According to Brønsted-Lowry what is a base
a proton acceptor
According to Arrhenius what is a strong acid (e.g. HNO3, HCl, H2SO4)
Substance that almost completely dissociates in water to give hydrogen ions
According to Brønsted-Lowry what is a strong acid (e.g. HNO3, HCl, H2SO4)
A good proton donor
According to Arrhenius what is a weak acid e.g. Ethanoic acid
Substance that only slightly dissociates in water to give hydrogen ions
According to Brønsted-Lowry what is a weak acid e.g. Ethanoic acid
A poor proton donor
According to Arrhenius what is a strong base
Substance that almost completely dissociates in water to give hydroxide ions
According to Brønsted-Lowry what is a strong base
A good proton acceptor
According to Arrhenius what is a weak base
Substance that only slightly dissociates in water to give hydroxide ions
According to Brønsted-Lowry what is a weak base
A poor proton acceptor
What is an alkali
A base that is soluble in water
What are the limitations to Arrhenius’s theory of acids and bases (according to his theory)
- H+ ions do not exist on their own in solution. They form the H3O+ ion
- Arrhenius’s definitions are restricted to aqueous solutions. Water is not the only solvent: other solvents include liquid ammonia and benzene.
E.g. NH4 + HCl <=> NH4Cl
According to Arrhenius’s definition of acids and based, the above reaction would not be classed as an acid-base reaction because the reaction doesn’t happen in water.
- NH3 can’t be considered a base- doesn’t dissociate go OH- ions in solution
- water cannot be considered amphoteric (act as both an acid and base)
Compare Arrhenius theory
- theory restricted to aqueous solutions
- Bases produce OH- ions in water
- some items cannot be classified as acids/bases due to strict definition (e.g. NH3 is not considered a base according to Arrhenius’s def)
- does not take hydronium ion formation into account
- does not explain how some substances can act as both an acid and a base in some reactions (amphoteric)
Compare Brønsted-Lowry’s theory
- not restricted to aqueous solutions and can involve reactions that occur in the gaseous state
- not all bases produce OH- ions in solutions. NH3 is a base and does not produce OH- ions.
- broader range of acids and bases
- takes hydronium ion formation into account
- explains in terms of proton transfer how some substances can be amphoteric e.g. water and HpO4-2
When does an acid become a conjugate base?
When it donates a proton
When does a base become a conjugate acid
When it accepts a proton
What is a conjugate acid base pair
Any pair consisting of in acid and a base that differ by a proton
An acid becomes it’s conjugate base after it has donated a proton
