1 Acids and Bases Chapter 15 Chemistry chapter 15

Chemistry chapter 15 1

Acids and Bases

Chapter 15


Overview

Many acids are found in foods. They usually taste sour or tart.Bases are found in many household cleaners and some foods. They often taste bitter.


Acids

Aqueous solutions of acids taste sour.Often corrosive and/or poisonous

Acids change the color of acid-base indicators in predictable ways.Acids react with bases to produce salts and water.Some acids undergo single-replacement reactions with active metals to release hydrogen gas.Some acids are electrolytes.


Binary acids

Contain only two different elements

Hydrogen and a more electronegative element


Naming binary acids

In pure form, they are gases.In aqueous solutions, they are known by their acid names.Always begin with the prefix hydro-Then add the root of the name of the other elementFinally, add the suffix - ic


Oxyacids

An acid that is a compound of hydrogen, oxygen, and a third element, usually a nonmetal.One type of ternary acids (containing three elements).Usually written as one or more hydrogen atoms followed by a polyatomic anion.Names are based on the anion.



Sulfuric Acid

The most commonly produced industrial chemical

Over 47 million tons made per year in US

UsesPetroleum refiningFertilizer manufacturingBattery acid


Sulfuric Acid

Dehydrating agentRemoves water

Causes serious burns by attacking organic compounds in skin


Nitric Acid

Volatile, unstable liquidBecomes more stable when dissolved in water

Stains proteins yellowCauses serious burnsHas a suffocating odorUsed to make explosives, among other things


Phosphoric Acid

Used to manufacture fertilizers and animal feedWhen dilute, provides a pleasant, yet sour, taste to beverages.Used as a cleaning agentUsed to make detergents


Hydrochloric Acid

Produced in your stomachUsed to “pickle” iron and steel

Remove surface impurities

Used for cleaningMuriatic acid – weak HCl

Used in swimming pools and for cleaning


Acetic Acid

Pungent-smelling liquidCalled glacial acetic acid – freezes at 17 °C.The acid in vinegarUsed to manufacture plasticsUsed in food supplementsUsed as a fungicide


Discuss

Logic in the laboratoryPage 463


Bases

Aqueous solutions taste bitterOften caustic

Change the color of indicators in predictable waysDilute aqueous solutions feel slipperyReact with acids to produce salts and waterAre electrolytes


Arrhenius acids

Increase the concentration of hydrogen ions (H+) in aqueous solutions


Arrhenius Bases

Increase the concentration of hydroxide, OH- ions , in aqueous solutions.

Could contain hydroxide and dissociateCould react with water to form hydroxide ions


Aqueous acids

Ionizable hydrogen atomsElectrolytesPolar molecules – hydrogen gets stolen by water to form hydronium ions.

The anion is left alone


Strong Acids

One that ionizes completely in aqueous solution.

PerchloricHydrochloricNitric

Strong electrolytesDepends on the polarity of the bond with hydrogen and the difficulty of breaking that bond.


Weak acids

Weak electrolytesSolutions contain hydronium ions, anions, and molecules.SulfuricHydrofluoric


Organic Acids

Contain the carboxyl group – COOHGenerally weak acids


Solutions of bases

Most bases are ionic, so they dissociate in solution.When a base dissociates completely, the solution is alkaline.

Li, Na, K, Rb, Cs (alkali metals)


Molecular bases

Produces a base when it reacts with water.

)()()()( 423 aqOHaqNHlOHaqNH


Strong bases

Strong electrolytesDepend on the extent to which the base dissociates or adds hydroxide ions to solution.


Discuss

Section Review on page 462


Brønsted-Lowry Acids

Molecules or ions that are proton donors

Includes all Arrhenius acids (H+ is a proton)Also includes other substances, like ions


Examples

HCl + NH3 NH4+ + Cl-

Brønsted-Lowry, but not ArrheniusNo hydrogen or hydronium ions

H2O + NH3 NH4+ + OH-

Water can be a Brønsted-Lowry acid


Brønsted-Lowry bases

Molecules or ions that are proton acceptors


Most Arrhenius bases are not Brønsted-Lowry bases

Since they are ionic compounds, they don’t accept protons


Brønsted-Lowry acid-base reaction

Protons are transferred from the acid to the base



Monoprotic acids

Can donate only one proton (hydrogen ion) per molecule

HClO4

HClHNO3


Polyprotic acids

Can donate more than one proton per molecule

H2SO4

H3PO4

Lose hydrogen atoms one at a timeDiprotic – can donate 2Triprotic – can donate 3


Lewis acid

An atom, ion, or molecule that accepts an electron pair to form a covalent bondDoes not have to contain hydrogenAny compound in which the central atom has three valence electrons and forms three covalent bonds can be a Lewis acid by forming a fourth covalent bond.


Lewis base

An atom, ion, or molecule that donates an electron pair to form a covalent bond


Lewis acid-base reaction

The formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor.


Discuss

Table 15-5 on page 468Section Review, page 468


Conjugate base

What is left after a Brønsted-Lowry acid gives up a proton.

OHFOHHF 3base conjugate

2acid


Conjugate acid

What is formed when a Brønsted-Lowry base gains a proton

acid conjugate3

base2

OHFOHHF


Conjugate acid and base strength

The stronger an acid, the weaker its conjugate base.The stronger a base, the weaker its conjugate acid.


Reaction direction

Proton-transfer reactions favor the production of the weaker acid and the weaker baseSee table 15-6 on page 471

4324 ClOOHOHHClO

COOCHOHOHCOOHCH 3323


Amphoteric compounds

Something that can react as either an acid or a baseIf reacting with a stronger acid than itself, acts as a baseIf reacting with a weaker acid, acts as an acid


Hydroxyl group

Covalently bonded –OH groupThe more polar the O-H bond, the more acidic the compound is.

Hydrogen is attracted away by the water in solution


Neutralization Reactions

In aqueous solutions, acids and bases react to neutralize each other and form a salt and water.

AntacidsBaking powder


Neutralization

If we write the net ionic equation, we get H3O+ + OH- 2H2O

Neutralization: the reaction of hydronium and hydroxide ions to make water


Acid Rain

Many gases produced by industrial processes can dissolve in atmospheric water to produce acids.Leads to acid rain or snow.Acids react with calcium carbonate in marble and erodes it.


Discuss

Which way do proton-transfer reactions go?How do you know which acid or base is stronger?What is a conjugate acid?What is a conjugate base?Section review #1 on page 475

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1 Acids and Bases Chapter 15 Chemistry chapter 15