Understanding Acids, Bases, and Salts

Arrhenius Theory

A theory explaining the behavior of many acids and bases.

Electrolyte

A substance which, when dissolved in water, forms a solution capable of conducting an electric current.

Concentration of Ions

The amount of ions present in a solution, which affects its ability to conduct electricity.

Properties of Acids

Acids dissolve in water, are electrolytes, taste sour, neutralize bases, react with active metals, and turn blue litmus red.

Properties of Bases

Bases dissolve in water, are electrolytes, taste bitter, neutralize acids, emulsify fats and oils, feel slippery, and have a pH more than 7.

pH of Acids

Acids have a pH less than 7.

pH of Bases

Bases have a pH more than 7.

Hydrochloric Acid

HCl(aq), hydrochloric acid is an electrolyte.

Hydrogen Ion

H+(aq), the only positive ion in an aqueous solution of an Arrhenius acid.

Hydronium Ion

H3O+(aq), a representation of the hydrogen ion in solution.

Arrhenius Bases

Arrhenius bases yield OH-(aq), hydroxide ion as the only negative ion in an aqueous solution.

Neutralization Process

An Arrhenius acid and an Arrhenius base react to form a salt and water.

Salt Formation

The nonmetal from the acid combines with the metal from the base to make a salt.

Water Formation in Neutralization

The H+ from the acid combines with the OH- from the base to make water (HOH = H2O).

Ammonia as a Base

When ammonia (NH3) dissolves in water, it produces hydroxide ions.

Hydroxide Ion

OH-(aq), the only negative ion produced when an Arrhenius base is dissolved in water.

Acetic Acid

An organic chemist would write the formula for acetic acid in a specific way.

Common Acids

Acids start with H, as listed in Table K.

Common Bases

Bases are listed in Table L.

Conductivity of NaOH

NaOH would conduct electricity if it was dissolved in water, not as a solid.

Conductivity of CH3OH

CH3OH is an alcohol, a non-electrolyte.

Conductivity of H2O

Water is a non-electrolyte, even as a liquid.

Neutralization Reaction

A reaction between an acid and a base that produces a salt and water.

Titration

A laboratory process in which a volume of solution of known concentration is used to determine the concentration of another solution.

MaxVa = MbxVb

Formula used in titration where Ma is the molarity of the acid, Mb is the molarity of the base, Va is the volume of the acid, and Vb is the volume of the base.

Equivalence Point

The point in a titration where the moles of H+ equals the moles of OH-.

HCl(aq) + NaOH(aq)

The reaction produces NaCl(aq) + HOH.

H2SO4(aq) + Ca(OH)2(aq)

The reaction produces CaSO4(aq) + 2H2O.

Regents Question: 06/02 #25

Given the reaction HCl(aq) + LiOH(aq) produces HOH(l) + LiCl(aq), the reaction is best described as neutralization.

Regents Question: 06/03 #30

Which equation represents a neutralization reaction? (4) H2SO4 + Mg(OH)2 produces MgSO4 + 2 H2O.

Concentration of HNO3

When 50. milliliters of an HNO3 solution is exactly neutralized by 150 milliliters of a 0.50 M solution of KOH, the concentration of HNO3 is 1.0 M.

Volume of NaOH solution

To neutralize 10.0 mL of the standard HCl solution in trial 3, the volume of NaOH solution used is calculated based on the titration data.

Bromthymol Blue

An indicator that changes color at a neutral pH (7), appropriate for determining the end point of a titration.

Phenolphthalein

An indicator that changes color right after being neutral, used in titrations.

Average Molarity of NaOH

Calculated as (1.0 + 1.1 + 1.0 + 0.96)/4 = 1.015, rounded to 1.0 M.

Acid-Base Theories

One theory states that an acid is an H+ (proton) donor and a base is an H+ (proton) acceptor.

pH Value

The acidity or alkalinity of a solution can be measured by its pH value.

Indicators

Substances used to show the relative level of acidity or alkalinity of a solution.

HCl donates a proton

In the reaction between NH3 and HCl, HCl acts as the proton donor.

NH3 accepts a proton

In the reaction between NH3 and HCl, NH3 acts as the proton acceptor.

Molarity of OH-

In titration, Mb represents the molarity of the hydroxide ion.

Volume of Acid

In titration, Va represents the volume of the acid solution used.

Volume of Base

In titration, Vb represents the volume of the base solution used.

Red Litmus

Turns Blue in Base

Blue Litmus

Turns Red in Acid

Methyl Orange at pH 3

Red

Methyl Orange at pH 5

Yellow

Methyl Orange at pH 7

Yellow

Methyl Orange at pH 9

Yellow

Bromthymol Blue at pH 3

Yellow

Bromthymol Blue at pH 5

Yellow

Bromthymol Blue at pH 7

Green

Bromthymol Blue at pH 9

Blue

Bromcresol Green at pH 3

Yellow

Bromcresol Green at pH 5

Green

Bromcresol Green at pH 7

Blue

Bromcresol Green at pH 9

Blue

Thymol Blue at pH 3

Blue

Thymol Blue at pH 5

Yellow

Thymol Blue at pH 7

Yellow

Thymol Blue at pH 9

Yellow

Thymol Blue at pH 10

Green

[H3O+] Formula

[H3O+] = 1 x 10^-pH

Hydronium Ion Concentration

An acid with a pH of 2 has 10x the [H3O+] concentration as an acid with a pH of 3.

Base Hydronium Ion Concentration

A base with a pH of 10 has 100x the [H3O+] concentration as a base with a pH of 12.

pH Scale

Each decrease of one unit of pH represents a tenfold increase in hydronium ion concentration.