Cumulative Skills

Metric Conversions

Understanding and converting between metric units is essential in chemistry for accurate measurement and calculation.

• Metric Prefixes: Common prefixes include kilo- (k, 103), centi- (c, 10-2), milli- (m, 10-3), micro- (μ, 10-6), and nano- (n, 10-9).

• Conversion Example: To convert 250 mg to grams:

Dimensional Analysis

Dimensional analysis is a systematic method for converting between units using conversion factors.

• Key Steps: Identify the starting unit, the desired unit, and set up conversion factors so units cancel appropriately.

• Example: Convert 5.0 miles to kilometers:

Chemical Nomenclature

Chemical nomenclature is the system for naming chemical compounds according to standardized rules.

• Ionic Compounds: Name the cation first, then the anion (e.g., NaCl is sodium chloride).

• Covalent Compounds: Use prefixes to indicate the number of atoms (e.g., CO2 is carbon dioxide).

• Acids: Binary acids use the prefix "hydro-" and suffix "-ic" (e.g., HCl is hydrochloric acid).

Chapter 4: Chemical Reactions & Stoichiometry

Balancing Non-Redox Chemical Equations

Balancing chemical equations ensures the law of conservation of mass is obeyed. Phases (s, l, g, aq) should be included.

• Steps: Write correct formulas, count atoms, adjust coefficients, and check your work.

• Example:

Stoichiometric Calculations Using Dimensional Analysis

Stoichiometry involves quantitative relationships between reactants and products in a chemical reaction.

• Key Steps: Convert given quantities to moles, use mole ratios from the balanced equation, and convert to desired units.

• Example: How many grams of CO2 are produced from 10.0 g of C6H12O6?

• Equation:

Relating Grams, Moles, and Molecules

Conversions between mass, moles, and number of particles use molar mass and Avogadro's number.

• Molar Mass: The mass of one mole of a substance (g/mol).

• Avogadro's Number: particles/mol.

• Example:

Limiting Reagent

The limiting reagent is the reactant that is completely consumed first, limiting the amount of product formed.

• Identification: Calculate the amount of product each reactant can produce; the smallest amount indicates the limiting reagent.

• Example: If 5.0 g of A reacts with 10.0 g of B, determine which is limiting.

Theoretical, Actual, and Percent Yield

Yields measure the efficiency of a chemical reaction.

• Theoretical Yield: Maximum amount of product possible, calculated from stoichiometry.

• Actual Yield: Amount of product actually obtained from the experiment.

• Percent Yield:

Chapter 5: Aqueous Reactions & Acid–Base Chemistry

Molarity and Percent Concentrations

Molarity and percent concentration are ways to express the concentration of a solution.

• Molarity (M):

• Percent by Mass (w/w):

• Example: Calculate the molarity of 5.00 g NaCl in 250 mL solution.

Solution Stoichiometry

Solution stoichiometry involves calculations with reactants and products in solution, considering limiting and excess reagents.

• Key Steps: Use molarity to find moles, apply stoichiometry, and convert to desired units.

• Example: How many moles of AgCl will precipitate from mixing 0.100 L of 0.200 M AgNO3 with excess NaCl?

Using Molarity in Mass, Volume, and Dilution Calculations

Molarity is used to relate the amount of solute to the volume of solution, and to perform dilution calculations.

• Equation: (for dilutions)

• Example: What volume of 2.0 M HCl is needed to prepare 500 mL of 0.50 M HCl?

Classification of Electrolytes

Electrolytes are substances that conduct electricity when dissolved in water.

• Strong Electrolytes: Completely dissociate (e.g., NaCl, HCl).

• Weak Electrolytes: Partially dissociate (e.g., CH3COOH).

• Non-Electrolytes: Do not dissociate (e.g., sugar, ethanol).

Strong and Weak Acids and Bases

Acids and bases are classified by their degree of ionization in water.

• Strong Acids: HCl, HBr, HI, HNO3, HClO4, H2SO4

• Strong Bases: LiOH, NaOH, KOH, RbOH, CsOH, Ba(OH)2

• Weak Acids/Bases: Partially ionize (e.g., HF, NH3).

Conjugate Acid–Base Pairs

A conjugate acid–base pair consists of two species that differ by one proton (H+).

• Example: NH3 (base) and NH4+ (conjugate acid).

Neutralization Reactions

Neutralization occurs when an acid reacts with a base to produce water and a salt.

• General Equation:

• Example:

Titration Calculations

Titration is a technique to determine the concentration of an unknown solution using a solution of known concentration.

• Key Equation: (for monoprotic acid-base titrations)

• Example: Calculate the concentration of HCl if 25.0 mL is neutralized by 30.0 mL of 0.10 M NaOH.

pH and [H+]

pH is a measure of the hydrogen ion concentration in a solution.

• pH Formula:

• Calculating [H+]:

• Classification: pH < 7 (acidic), pH = 7 (neutral), pH > 7 (basic)

Solubility Rules and Precipitation

Solubility rules help predict whether a precipitate will form in a reaction.

• Common Soluble Compounds: Nitrates (NO3-), alkali metal salts, ammonium (NH4+).

• Common Insoluble Compounds: Carbonates (CO32-), phosphates (PO43-), except with alkali metals or NH4+.

• Example: Mixing AgNO3 and NaCl forms AgCl(s) precipitate.

Molecular, Total Ionic, and Net Ionic Equations

These equations represent chemical reactions in aqueous solution at different levels of detail.

• Molecular Equation: Shows all reactants and products as compounds.

• Total Ionic Equation: Shows all strong electrolytes as ions.

• Net Ionic Equation: Shows only the species that change during the reaction.

• Example:

  • Molecular:

  • Total Ionic:

  • Net Ionic:

Spectator Ions

Spectator ions are ions that do not participate in the actual chemical change and appear unchanged on both sides of the total ionic equation.

• Example: In the reaction above, Na+ and NO3- are spectator ions.