Acids

Acids are substances that, when dissolved in a solution, release hydrogen ions (H+) as the primary positive ions. In simpler terms, acids donate protons in an aqueous solution.

Properties

• Have a sour taste resembling vinegar or lemon juice
• Turn blue litmus paper red
• Conduct electricity
• React with active metals, producing hydrogen gas with a distinct popping sound near a lit splint
• Generate hydrogen ions in an aqueous solution

pH

The pH scale is a numerical representation that indicates whether a solution is acidic, alkaline (basic), or neutral:

• Acidic solutions have a pH below 7, but not exactly 7.
• Neutral solutions have a pH of 7.

Indicators

Dyes used to identify acids by displaying one color and bases (alkaline substances) by showing another color. Indicators help differentiate between acidic and basic/neutral solutions.

Mineral Acid

These acids originate from minerals found in the environment, such as hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), and phosphoric acid (H3PO4).

Organic Acid

These acids are obtained from plants and other organic materials, including ethanoic acid (CH3COOH) found in vinegar, tartaric acid (C4H6O6) found in grapes, citric acid (C6H8O7) found in citrus fruits, and lactic acid (C3H6O3).

Strong Acid

These acids completely ionize in an aqueous solution, resulting in efficient electrical conductivity. Examples include hydrochloric acid (HCl) and sulfuric acid (H2SO4).

Weak Acid

These acids only partially ionize in an aqueous solution, resulting in limited electrical conductivity. Examples include ethanoic acid (CH3COOH) and citric acid (C6H8O7).

Monobasic Acids

These acids yield one free H+ ion, such as hydrochloric acid, nitric acid, ethanoic acid, and lactic acid.

Dibasic Acids

These acids yield two free H+ ions or molecules of acid in an aqueous solution, such as sulfuric acid and tartaric acid.

Tribasic Acids

These acids yield three H+ ions per molecule of acid in an aqueous solution, such as phosphoric acid.

Acid Anhydrides

These compounds react with water to form acids. Many acid anhydrides are acidic oxides of non-metals, including carbon dioxide, sulfur dioxide, sulfur trioxide, and nitrogen dioxide.

Reaction of Acids

Acids use their hydrogen ions (H+) to react with various substances.

• Active Metals: Acids react with active metals like lithium, calcium, and sodium, producing a metal salt and hydrogen gas. Example: 2HCl + 2Na → 2NaCl + H2
• Metal Carbonate/Hydrogen: The reaction between an acid and a metal carbonate/hydrogen produces a metal salt, carbon dioxide, and water. Example: 2HCl + CaCO3 → CaCl2 + CO2 + H2O

Bases/Alkali

This type of reaction produces a metal salt and water, known as neutralization. Example: H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O

Bases

Bases

Bases include metal oxides (e.g., CaO), metal hydroxides (e.g., Ca(OH)2), and ammonia (NH3(aq)). A base accepts protons and releases OH- ions in an aqueous solution.

Alkalis

Alkalis are bases that can dissolve or are soluble in water, such as sodium hydroxide (NaOH(aq)).

Properties of Bases

• Have a bitter taste
• Corrosive
• Turn red litmus paper blue
• Have a pH greater than 7
• Conduct electricity when in an aqueous state
• Neutralize acids, forming salts and water
• Produce hydroxide ions (OH-) in an aqueous solution
• Give a slippery sensation when touched due to the conversion of skin oils to soap

Reactions of Alkalis

• Metal Ions: In these reactions, metal ions bond with non-metal atoms or covalently bonded anions, producing different alkalis/bases and a different metal ion. Example: 2KCl(aq) + Mg(OH)2 → 2KOH(aq) + MgCl2(aq)
• Ammonium Salts: An ammonium salt forms when an ammonium cation (NH4+) bonds with an anion or covalently bonded anion molecules, yielding a different salt, water, and ammonia gas (NH3). Example: (NH4)2SO4(aq) + Ca(OH)2(aq) → CaSO4(aq) + 2H2O + 2NH3(g)

Categorizing Bases

Alkalis serve as a category for bases that are soluble in water. Two other categories are weak and strong alkalis.

Weak Alkalis

Weak alkalis partially ionize in an aqueous solution, forming hydroxide ions and a cation similar to an acid. Example: Cu(OH)2 → Cu2+(aq) + 2OH-(aq) (partial ionization)

Strong Alkalis

Strong alkalis fully ionize, yielding a high concentration of hydroxide ions and cations. Example: NaOH(aq) → Na+(aq) + OH-(aq) (complete ionization)

Precipitate

Precipitates are insoluble ionic solid products formed when specific cations and anions combine in an aqueous solution. For example, when mixing sodium hydroxide (NaOH(aq)) and iron(III) chloride (FeCl3(aq)), iron hydroxide (Fe(OH)3(s)) precipitate forms. Example: 3NaOH(aq) + FeCl3(aq) → Fe(OH)3(s) + 3NaCl(aq)

Josiah Renne "PC"