Stoichiometry and Chemical Reactions

Stoichiometry: Mass-Mass Calculations

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It allows chemists to predict the amounts of substances consumed and produced.

• Definition: Stoichiometry uses balanced chemical equations to relate the masses of reactants and products.

• Key Steps:

  1. Write and balance the chemical equation.

  2. Convert given quantities to moles using molar mass.

  3. Use mole ratios from the balanced equation to find moles of desired substance.

  4. Convert moles back to grams if required.

• Example: Given: . To find how many grams of AgPO can be formed from 12.0g AgNO$_3$ and 8.0g Na$_3$PO$_4$, convert each to moles, use the limiting reagent, and calculate the mass of product.

Additional info: Limiting reagent is the reactant that is completely consumed first, limiting the amount of product formed.

Limiting Reagent

The limiting reagent determines the maximum amount of product that can be formed in a reaction.

• Definition: The reactant that is used up first in a chemical reaction.

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

Thermochemical Equations and Calculations

Thermochemical equations include energy changes, typically as heat, associated with chemical reactions.

• Example: is produced from in a reaction. Calculate the mass of $\text{Al}_2\text{O}_3$ formed from 10,000.0g $\text{Al}$ using the reaction's stoichiometry.

Electrons in Atoms and the Periodic Table

Electron Arrangement and Periodic Trends

The arrangement of electrons in atoms determines chemical properties and periodic trends.

• Electron Configuration: The distribution of electrons among atomic orbitals.

• Periodic Trends:

  • Atomic Radius: Generally increases down a group and decreases across a period.

  • Ionization Energy: Energy required to remove an electron; increases across a period, decreases down a group.

  • Metallic Character: Increases down a group, decreases across a period.

• Example: Explain why atomic radius increases down a group and decreases across a period.

Valence Electrons and Lewis Structures

Valence electrons are the outermost electrons involved in chemical bonding. Lewis structures represent the arrangement of valence electrons around atoms.

• Definition: Valence electrons are electrons in the highest energy level of an atom.

• Lewis Structure: Diagram showing bonds and lone pairs in a molecule.

• Example: Draw the Lewis structure for , , and .

Chemical Bonding

Types of Chemical Bonds

Chemical bonds are forces that hold atoms together in compounds. The main types are ionic, covalent, and polar covalent bonds.

• Ionic Bonds: Formed by transfer of electrons from metals to nonmetals.

• Covalent Bonds: Formed by sharing electrons between nonmetals.

• Polar Covalent Bonds: Unequal sharing of electrons due to differences in electronegativity.

• Electronegativity: The ability of an atom to attract electrons in a bond.

• Example: Use electronegativity values to determine bond type in and .

Gases and Gas Laws

Properties of Gases

Gases have unique properties such as compressibility, expansion, and low density. Their behavior is described by several gas laws.

• Pressure: Force exerted by gas particles on container walls. Units include atm, kPa, mmHg, and psi.

• Factors Affecting Pressure: Volume, temperature, and number of particles.

• Conversion: Be able to convert between pressure units.

Gas Laws

Gas laws describe the relationships between pressure, volume, temperature, and amount of gas.

• Boyle's Law: (at constant temperature)

• Charles's Law: (at constant pressure)

• Combined Gas Law:

• Ideal Gas Law:

• Dalton's Law of Partial Pressures:

• Example: Calculate the volume of a gas at different conditions using the ideal gas law.

Applications of Gas Laws

• Example: Convert 1.3 atm to mmHg, calculate the pressure when a gas is heated, and determine the mass of KClO needed to form a certain amount of O at given conditions.

HTML Table: Comparison of Gas Laws

Additional info: The review covers key concepts from stoichiometry, chemical reactions, electron configuration, chemical bonding, and gas laws, all of which are foundational topics in introductory college chemistry.