Chapter 4.1-4.3Aqueous ReactionsChapter 4.1-4.3

Aqueous Reactions

Aqueous SolutionsAqueous

Solutions Aqueous solutions are solutions in which water is the dissolving medium. Use (aq) for the state of a substance dissolved in water.

Remember that a solution is a homogenous mixture of at least two substances.

Solvent: substance present in greater quantity

Solute: substance dissolved in the solvent

Aqueous solutions are solutions in which water is the dissolving medium. Use (aq) for the state of a substance dissolved in water.

Remember that a solution is a homogenous mixture of at least two substances.

Solvent: substance present in greater quantity

Solute: substance dissolved in the solvent

Electrolytic Properties

Electrolytic Properties

Electrolytes: substances that produce ions in aqueous solutions. Ionic compounds are generally good electrolytes because they break down into ions. Electrolytes conduct electricity.

Ex: Put NaCl into water and it breaks apart into Na+ and Cl- ions surrounded by water molecules.

Electrolytes: substances that produce ions in aqueous solutions. Ionic compounds are generally good electrolytes because they break down into ions. Electrolytes conduct electricity.

Ex: Put NaCl into water and it breaks apart into Na+ and Cl- ions surrounded by water molecules.

Strong and Weak Electrolytes

Strong and Weak Electrolytes

Strong electrolytes: dissolve almost completely into ions; good electrical conductors.

Ex: HCl (aq) H+(aq) + Cl-

(aq)

Weak electrolytes: exist in water mostly as molecules; only a slight formation of ions.

Ex: HC2H3O2 (aq) H+(aq) + C2H3O2

- (aq)

Strong electrolytes: dissolve almost completely into ions; good electrical conductors.

Ex: HCl (aq) H+(aq) + Cl-

(aq)

Weak electrolytes: exist in water mostly as molecules; only a slight formation of ions.

Ex: HC2H3O2 (aq) H+(aq) + C2H3O2

- (aq)

NonelectrolytesNonelectrolytes Nonelectrolytes: substances that do not form ions when placed in water.

Most molecular compounds dissolve without forming ions. Water molecules simply come in between individual molecules. No ions are formed.

Nonelectrolytes will not conduct electricity. Ex: pure water, sucrose solution

Note: Acids are molecules but will form ions in aqueous solution!

Nonelectrolytes: substances that do not form ions when placed in water.

Most molecular compounds dissolve without forming ions. Water molecules simply come in between individual molecules. No ions are formed.

Nonelectrolytes will not conduct electricity. Ex: pure water, sucrose solution

Note: Acids are molecules but will form ions in aqueous solution!

AcidsAcids Acids are substances that ionize in aqueous solution to form H+ ions.

If the amount of H+ increases, pH decreases (pH < 7).

H+ = a proton, so acids are often called “proton donors”.

Therefore, all acids will have hydrogen in the formula, usually written at the beginning. Always include (aq) with an acid formula!

Acids are substances that ionize in aqueous solution to form H+ ions.

If the amount of H+ increases, pH decreases (pH < 7).

H+ = a proton, so acids are often called “proton donors”.

Therefore, all acids will have hydrogen in the formula, usually written at the beginning. Always include (aq) with an acid formula!

Monoprotic and Polyprotic AcidsMonoprotic and

Polyprotic Acids Monoprotic acids: yield one H+ ion per molecule of acid. Ex: HCl(aq)

Diprotic acids: yield two H+ ions per molecule of acid. Ex: H2SO4(aq)

1st step: H2SO4(aq) H+(aq) + HSO4

-(aq)

2nd step: HSO4-(aq) H+

(aq) + SO42-(aq)

Triprotic Acids: yield three H+ions per molecule of acid. Ex: H3PO4(aq). These acids would have three steps to remove the hydrogen ions from the molecule.

Monoprotic acids: yield one H+ ion per molecule of acid. Ex: HCl(aq)

Diprotic acids: yield two H+ ions per molecule of acid. Ex: H2SO4(aq)

1st step: H2SO4(aq) H+(aq) + HSO4

-(aq)

2nd step: HSO4-(aq) H+

(aq) + SO42-(aq)

Triprotic Acids: yield three H+ions per molecule of acid. Ex: H3PO4(aq). These acids would have three steps to remove the hydrogen ions from the molecule.

BasesBases Bases produce OH- ions in aqueous sol’n, making the pH higher than 7.

Bases are known as “proton acceptors”.

All hydroxides (NaOH, KOH) are bases, but not all bases are hydroxides.

For example, NH3 is a base because it produces hydroxide ion in water: NH3(aq) + H2O(l) NH4

+(aq) + OH-

(aq)

Bases produce OH- ions in aqueous sol’n, making the pH higher than 7.

Bases are known as “proton acceptors”.

All hydroxides (NaOH, KOH) are bases, but not all bases are hydroxides.

For example, NH3 is a base because it produces hydroxide ion in water: NH3(aq) + H2O(l) NH4

+(aq) + OH-

(aq)

Strong Acids and Strong Bases

Strong Acids and Strong Bases

Strong acids and strong bases are strong electrolytes.

Memorize these strong acids: HCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4

Memorize these strong bases (meat cleaver): LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2

Acids and bases not listed above are considered weak acids or bases and are weak electrolytes. Non-soluble bases are NON ELECTROLYTES

Strong acids and strong bases are strong electrolytes.

Memorize these strong acids: HCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4

Memorize these strong bases (meat cleaver): LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2

Acids and bases not listed above are considered weak acids or bases and are weak electrolytes. Non-soluble bases are NON ELECTROLYTES

Table 4.3: Electrolytic Behavior

Table 4.3: Electrolytic Behavior

Strong, Weak, or Nonelectrolytes?Strong, Weak, or Nonelectrolytes?

CaCl2

Strong: soluble ionic cmpd

HNO(aq)

Strong: strong acid

C2H5OH Nonelectrolyte: molecule

KOH Strong: soluble ionic cmpd

NH3

Weak: weak base

H3PO4(aq)

Weak: weak acid

Neutralization Reactions

Neutralization Reactions

Neutralization reactions are double replacement reactions in which we mix an acid with a base.

The mixing of a strong acid and a strong base will produce a salt and water.

HCl(aq)+ NaOH(aq) NaCl(aq)+ H2O(l)

Salt: any ionic cmpd whose cation comes from a base and whose anion comes from an acid.

Neutralization reactions are double replacement reactions in which we mix an acid with a base.

The mixing of a strong acid and a strong base will produce a salt and water.

HCl(aq)+ NaOH(aq) NaCl(aq)+ H2O(l)

Salt: any ionic cmpd whose cation comes from a base and whose anion comes from an acid.

Acid-Base Reactions With Gas

Formation

Acid-Base Reactions With Gas

Formation Other bases besides hydroxides will react with acids to form salts and gases with low solubility in water.

Sulfides react with acids to form hydrogen sulfide gas. 2HCl(aq)+ Na2S(aq) H2S(g)+ 2NaCl(aq)

Carbonates and bicarbonates react with acids to form carbon dioxide gas. HCl(aq)+ NaHCO3(aq) NaCl(aq)+ H2CO3(aq)

H2O(l) + CO2 (g)

(At normal room temperature and pressure carbonic acid will decompose into water and carbon dioxide.)

Other bases besides hydroxides will react with acids to form salts and gases with low solubility in water.

Sulfides react with acids to form hydrogen sulfide gas. 2HCl(aq)+ Na2S(aq) H2S(g)+ 2NaCl(aq)

Carbonates and bicarbonates react with acids to form carbon dioxide gas. HCl(aq)+ NaHCO3(aq) NaCl(aq)+ H2CO3(aq)

H2O(l) + CO2 (g)

(At normal room temperature and pressure carbonic acid will decompose into water and carbon dioxide.)