Chemistry Regents: Acids, Bases, and Salts - In Depth Notes

Chemistry Regents: Acids, Bases, and Salts - In Depth Notes

Properties of Acids

  • Taste: Acids have a sour taste.

  • Electrolytes: They can conduct electricity when dissolved in water.

  • Indicators: Acids cause acid-base indicators to change color. For example:

    • Blue litmus paper turns red in the presence of an acid.

  • Reactions:

    • React with bases to produce water and a salt.

    • React with metals (except Cu, Ag, and Au) to produce hydrogen gas (H2).

Properties of Bases

  • Taste: Bases have a bitter taste.

  • Texture: They feel slippery to the touch.

  • Electrolytes: Bases can also conduct electricity when dissolved.

  • Reactions:

    • React with acids to produce water and a salt.

  • Indicators: Bases change the color of acid-base indicators as well.

Acid Nomenclature

  • Hydrogen Start: All acids begin with H.

  • Two Elements: If the acid has two elements (H + another element):

    • Use the naming format hydro- + stem + -ic acid.

  • Three or More Elements: If the acid contains three or more elements (H + polyatomic ion):

    • Do not use hydro, but change the ending as follows:

    • If the polyatomic ion ends in -ate, change to -ic acid.

    • If the polyatomic ion ends in -ite, change to -ous acid.

Definitions of Acid

  • Arrhenius Definition:

    • Acids produce H+ ions (or H3O+ - hydronium ion).

    • Bases produce OH- ions.

  • Bronsted-Lowery Definition:

    • Acids are proton donors (H+).

    • Bases are proton acceptors (H+).

    • Not all bases have -OH in their formula, e.g., NH3 is a base but does not contain an -OH group.

    • -COOH groups indicate organic acids, not bases.

pH Scale

  • Acidity and Basicity:

    • pH below 7: acidic

    • pH equal to 7: neutral

    • pH above 7: basic

  • Scale Interpretation: Each 1 unit change in pH represents a ten-fold change in [H+].

  • Relationship: [H+] + [OH-] = 14.

    • If one increases, the other decreases.

  • Calculating pH: pH = -log[H+].

pH Testing and Indicators

  • Litmus Paper:

    • Blue indicates basic.

    • Red indicates acidic.

  • pH Paper: Provides a range for determining pH.

  • Phenolphthalein: Changes from clear (acidic) to pink (basic).

  • Table M: Lists various indicators and their pH ranges.

Strong vs. Weak Acids and Bases

  • Strong Acids: Completely dissociate in solution.

  • Weak Acids: Do not completely dissociate; exist in equilibrium with undissociated species.

  • Strong and Weak Bases: Similar behavior as acids in terms of dissociation.

Acid Reactions with Metals

  • Reactivity: Only metals above hydrogen in activity series will react with acids to release H2.

  • General Reaction:

    • Acid + Metal → H2 + Salt (metal-nonmetal compound).

Neutralization Reactions

  • Equation: Acid + Base → Water + Salt.

  • Type: Double replacement reactions.

  • Equal Ion Concentration: In neutralization, [H+] ions = [OH-] ions.

Titration

  • Purpose: To find the concentration of an unknown acid or base using a standard solution.

  • Process:

    • Add a measured volume of a known concentration acid/base to the unknown solution until neutralization.

    • Use the formula MaVa = MbVb, where:

    • Ma = Molarity of acid

    • Va = Volume of acid

    • Mb = Molarity of base

    • Vb = Volume of base

  • Ion Ratio: Maintain a 1:1 ratio between [H+] and [OH-].

Reference Table Formulas

  • Molarity: M = moles/liters.

  • Moles Calculation: Moles = mass (g) / molar mass.

  • Calculating [H+]: For acids, take into account the number of H’s per molecule multiplied by moles of acid (e.g. for H2SO4, count 2 H’s).

Summary of Definitions

  • Acids:

    • Proton donors

    • Produce H+ ions

    • pH below 7

  • Bases:

    • Proton acceptors

    • Produce OH- ions

    • pH above 7