Reactivity 3.1.1-3.1.2 Bronsted Lowry Acis

proton transfer reaction

reactant loses H+ = loses positive charge

product gains H+ = gains positive charge

Bronsted-Lowry acid-base behaviour

type of reaction between certain species where reactants release H+ and products have a lone pair that can accommodate an additional H+

what does acid and base strength depend on

their equilibria in aqueous solutions

early theories for acid-base behaviour

France Lavoisier 1777:

oxygen is universal acidifying principle “acid = oxygen and nonmetal)

dismissed because of HCl

SWE Arrhenius 1887:

Almost correct, not general enough (only aqueous) = ”substance which dissociates in water to for H+ and anions= acid, substance for OH- and cations=base, the anions and cations can form a salt”

Bronsted Lowry theory

• BL Acid= proton donor

• BL Base= proton acceptor

H+ said

proton

conjugate acid base pair difference

one proton

conjugate acid-base pair

acids react to form bases and vice versa; the acid-base pairs related to each other in this way are conjugate

H+(aq)

H3O+

condition for a BL acid to behave as proton donor

base present to accept the proton

how to deduce formulas of conjugate acids and bases

• add an H for transition to base

• add +1 to charge for transition to base

• remove an H for transition to acid

• add -1 to charge for transition to base

alkalis

soluble bases which dissolve in water to release OH-

amphiprotic species

substances which can activation as both BL acids and bases

• must possess a lone pair of e-

• possess H that can be released as H+

periodicity “amphoteric”

from left to right, oxides transition from basic metal oxides through amphoteric oxides, which can react with both acids and bases to acidic oxides.

basic metal oxides

react with acids to form a salt and water

amphoteric oxides

react with both acids and bases to form a salt and water

non metal oxides

form weak acids in solution

acid rain

pH of precipitation<5.6, major environmental problem causing negative impact on structural materials, lakes and rivers, and plant life (especially coniferous forests)

nitrogen and sulfur oxides (NOX) and (SOX)

react with moisture in the atmosphere to form weak acids which can then further react to form stronger acids resulting in a complex mix of pollutants in the atmosphere