Aim: What are acids and bases?

Acids1. Acids can be strong or weak electrolytes in aqueous

solutions.2. Acids (ex: HCl) react with certain metals to produce

H2(g).3. Acids cause color changes in acid-base indicators:

Blue litmus paper turns red in an acidPhenolphthalein is colorless in an acid

4. Acids have a sour tasteTable K has a list of Common Acids

Bases

1. Bases can be strong or weak electrolytes in aqueous solutions

2. Bases cause color changes in acid-base indicators:Red litmus paper turns blue in a basePhenolphthalein is pink in a base

3. Bases feel slippery and taste bitter.Table L has a list of Common Bases

Arrhenius Acid

•An Arrhenius acid gives off H+ (hydrogen ions) in aqueous solutions.•Ex: HCl, HBr, H2SO4

•The H+ attach to H2O to form H3O+ (hydronium ion).•HCl + H2O H+ + Cl- + H2O Cl- + H3O+

Arrhenius Base

•An Arrhenius base has OH and give off OH- (hydroxide ions) in an aqueous solution.•Ex: NaOH, KOH, Ca(OH)2

•NaOH Na+ + OH-

•Group 1 metals react with water to produce bases.•2Na(s) + 2H2O(l) 2 NaOH(aq) +H2(g)

Question

Which substance can be classified as an Arrhenius acid?1. HCl2. NaCl3. LiOH4. KOH

Question

Which substance can be classified as an Arrhenius base?1. HCl2. NaOH3. LiNO3

4. KHCO3

Question

According to the Arrheneius theory, a substance that is classified as an acid will always yield1. H+(aq)2. NH+

4(aq)3. OH-(aq)4. CO3

2-(aq)

Bronsted-Lowry Acids and Bases

•An acid is an H+ donor(proton donor).•A base is an H+ acceptor (proton acceptor)

HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)

HCl is an acid because it donates an H+ to the H2O.

Donates H+

ACID

BASE

Accepts H+

Bronsted-Lowry Acids and Bases

NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

NH3 is a base because it accepts an H+ from the H2O.

Accepts H+

Donates H+

ACID

BASE

Bronsted-Lowry Acids and Bases

•Water can either be a proton donor (acid) or a proton acceptor (base); water is amphoteric.

Question

According to the Bronsted-Lowry theory, a chloride ion (Cl-), acts as a base when it combines with1. An OH- ion2. A K+ ion3. An H- ion4. An H+ ion

Question

According to the Bronsted-Lowry theory, an acid is1. A proton donor, only2. A proton acceptor, only3. A proton donor and a proton acceptor4. Neither a proton donor nor a proton acceptor

Conjugate acids and bases

NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

BASE ACID CONJUGATE CONJUGATEACID BASE

A conjugate base is what is remained after the acid gives up H+.A conjugate acid is what is formed when a base accepts a proton.

Question

In the reactionH2PO4

- + H2O H3PO4 + OH-

which pair represents an acid and its conjugate base?1. H2O and H2PO4

-

2. H2O and H3PO4

3. H3PO4 and OH-

4. H3PO4 and H2PO4-

Question

Given the reaction at equilibriumHSO4

- + H2O H3O+ + SO42-

According to the Bronsted-Lowry theory, the two bases are1. H2O and H3O+

2. H2O and SO42-

3. H3O+ and H2SO4-

4. H3O+ and SO42-