Acids and Bases: Properties, Identification, and Characteristics

Acids and Bases

Introduction to Acids

Acids are covalent compounds that contain a hydrogen ion connected to a nonmetal anion or a polyatomic ion. In most acids, the hydrogen is found at the beginning of the compound formula, except for acetic acid.

• Definition: An acid is a substance that donates hydrogen ions (H+) when dissolved in water.

• General Formula: Acids often have the form HX, where X is a nonmetal or polyatomic ion.

• Examples of Common Acids:

  • Hydrochloric acid: HCl

  • Hydrosulfuric acid: H2S

  • Hydrocyanic acid: HCN

  • Phosphoric acid: H3PO4

  • Acetic acid: CH3COOH

Example: Identifying Acid Structures

Which of the following does not represent the possible structure of an acid?

• a) HBr

• b) HIO3

• c) CH4 (Correct: Not an acid, as it does not contain a hydrogen ion bonded to a nonmetal or polyatomic ion)

• d) HOCl

Characteristics of Acids

Acids display distinct properties in aqueous solutions due to their ability to donate hydrogen ions.

• Dissociation: Acids dissociate in water to produce H+ ions.

  • Example: $\mathrm{HCl} (aq) \rightarrow \mathrm{H}^+ (aq) + \mathrm{Cl}^- (aq)$

  • Example: $\mathrm{H}_2\mathrm{SO}_4 (aq) \rightarrow 2\mathrm{H}^+ (aq) + \mathrm{SO}_4^{2-} (aq)$

• Taste and Feel: Acids typically have a sour taste.

• Reactivity: Acids react with metals to produce hydrogen gas.

  • Example: $\mathrm{Zn} (s) + 2\mathrm{HCl} (aq) \rightarrow \mathrm{ZnCl}_2 (aq) + \mathrm{H}_2 (g)$

• Litmus Paper Test: Acids turn blue litmus paper red.

Dissociation	Taste and Feel	Reactivity	Litmus Paper
Acids dissociate to release H+ ions in water	Sour taste	React with metals to produce H2 gas	Blue litmus turns red

Example: Acid Dissociation in Water

When H2SO4 is added to water, the solution contains more hydrogen ions, turns blue litmus paper red, and has fewer water molecules than the original water sample.

Introduction to Bases

Bases are ionic compounds containing a metal cation connected to the basic anion OH- (hydroxide), or they may be hydrogen-containing covalent compounds called amines.

• Definition: A base is a substance that accepts hydrogen ions or produces hydroxide ions (OH-) in water.

• General Formula: Bases often have the form MOH, where M is a metal.

• Examples of Common Bases:

  • Sodium hydroxide: NaOH

  • Potassium hydroxide: KOH

  • Strontium hydroxide: Sr(OH)2

  • Ammonia: NH3 (acts as a base by accepting H+)

Example: Identifying Base Structures

Which of the following does not represent the possible structure of a base?

• a) OHCH2

• b) NaCl (Correct: Not a base, as it does not contain OH- or an amine group)

• c) KOH

• d) HC2H3O2

Characteristics of Bases

Bases share common properties when dissolved in water, primarily due to the production of hydroxide ions.

• Dissociation: Bases dissociate in water to produce OH- ions.

  • Example: $\mathrm{NaOH} (aq) \rightarrow \mathrm{Na}^+ (aq) + \mathrm{OH}^- (aq)$

  • Example: $\mathrm{Sr(OH)}_2 (aq) \rightarrow \mathrm{Sr}^{2+} (aq) + 2\mathrm{OH}^- (aq)$

• Taste and Feel: Bases have a bitter taste and feel slippery to the touch.

• Litmus Paper Test: Bases turn red litmus paper blue.

Dissociation	Taste and Feel	Litmus Paper
Bases dissociate to release OH- ions in water	Bitter taste, slippery feel	Red litmus turns blue

Example: Properties of Strong Bases

• a) It has a sour taste.

• b) It turns blue litmus paper red.

• c) It releases H+ ions in solution.

• d) It can be used in the production of cleaning supplies. (Correct: Many strong bases are used in cleaning products due to their ability to break down organic materials.)

Practice: Properties of LiOH

• a) It has a sour taste.

• b) It produces H+ ions in water.

• c) It conducts an electrical current in solution. (Correct: Bases, like acids, conduct electricity in solution due to the presence of ions.)

• d) It decreases the OH- ions in water.

Additional info: The notes cover foundational concepts in GOB Chemistry regarding acids and bases, including their identification, dissociation, and characteristic properties. The tables and examples are reconstructed and expanded for clarity and completeness.