Review: Arrhenius Definition of Acids and Bases Acids produce H + in aqueous (water) solutions Acids produce H + in aqueous (water) solutions water water HCl H + (aq) + Cl - (aq) Bases produce OH - in aqueous (water) solutions Bases produce OH - in aqueous (water) solutions water water NaOH Na + (aq) + OH - (aq) NaOH Na + (aq) + OH - (aq)

The Brønsted-Lowry Definition of Acids and Bases Acid:PROTON DONOR can donate H + ions. Base:PROTON ACCEPTOR accepts H + ions. Broader Definition than Arrhenius

H + Transfer Acid/base reactions involve “proton transfer”. The reaction need not occur in water.

H + leaves one compound and is transferred to another. H + leaves one compound and is transferred to another. Ex: NH 3 + H 2 O NH OH - BaseAcid Follow the H +

Conjugate acid/base pairs: formulas differ by only a hydrogen ion, H +. The acid on one side becomes the base on the other side and vice versa. Ex: HCl + H 2 O H 3 O + + Cl - Acid BaseAcid Base

Conjugate acid contains one more H + in its formula

Label the Conjugate Acids and Bases in Each Reaction

Amphoteric/Amphiprotic Substances: Can act as either an acid or a base. Must have an “H” in formula (to donate) Must have a free e - pair (to accept a H + )

Water is amphoteric Water is amphoteric It can donate an H + or accept an H + It can donate an H + or accept an H + It depends on what it is combined with. It depends on what it is combined with.

Water donates H + to NH 3 forming the hydroxide ion (OH - ). Water accepts H + from HCl forming the hydronium ion (H 3 O + ).

When it can go either way… Amphoteric (amphiprotic) substances HCO 3 - H 2 CO 3 CO H + - H + Acting like a base Acting like an acid accepts H + donates H +

Let’s Practice What is the Brønsted-Lowry definition of an acid? What is the Brønsted-Lowry definition of an acid? 1) A substance that donates protons. 2) A substance that accepts protons. 3) A substance that dissolves in water to form ions. 4) A substance that dissolves in water to form ions.

If H 3 O + is an acid according to the Brønsted-Lowry theory, what is the conjugate base of this acid? If H 3 O + is an acid according to the Brønsted-Lowry theory, what is the conjugate base of this acid? 1) H 4 O +2 (aq) 2) H + (aq) 3) H 2 O (l) 4) OH - (aq)

According to one acid-base theory, water acts as an acid when an H 2 O molecule According to one acid-base theory, water acts as an acid when an H 2 O molecule (1) accepts an H+ (1) accepts an H+ (2) accepts an H- (3) donates an H+ (3) donates an H+ (4) donates an H-

One acid-base theory defines a base as an One acid-base theory defines a base as an (1) H+ donor (1) H+ donor (2) H donor (3) H+ acceptor (3) H+ acceptor (4) H acceptor

What is the conjugate base of H 2 PO 4 - What is the conjugate base of H 2 PO 4 - 1) H 3 O+ (aq) 2) H 3 PO 4 (aq) 3) HPO 4 -2 (aq) 4) PO 4 -3 (aq)

Online tutorial on Bronsted/Lowry Online tutorial on Bronsted/Lowry definitions-bronsted-lowry/acids-and- bases-definitions-bronsted-lowry-tutorial definitions-bronsted-lowry/acids-and- bases-definitions-bronsted-lowry-tutorial definitions-bronsted-lowry/acids-and- bases-definitions-bronsted-lowry-tutorial definitions-bronsted-lowry/acids-and- bases-definitions-bronsted-lowry-tutorial

Dilution water (solvent)solute concentrated, M initial diluted, M final adding water lowers the solute concentration moles of solute remain constant V initial V final moles initial = moles final M final x V final = M initial x V initial

Acid/Base Summary Films The Proton in Chemistry The Proton in Chemistry Acid and Base Tutorial: Acid Base Quiz Acid Bases Hydrogen Transfer (Neutralization)