Chapter 4: Chemical Reactions and Chemical Quantities

Balancing Chemical Equations

Balancing chemical equations ensures the law of conservation of mass is obeyed. Each side of the equation must have the same number of atoms for each element.

• Key Point: Adjust coefficients (not subscripts) to balance atoms.

• Example:

Mole–Mole Factor

The mole–mole factor is the ratio of coefficients from a balanced equation, used to convert between moles of reactants and products.

• Key Point: Use coefficients as conversion factors.

• Example: In , the mole–mole factor between and is 2:2 or 1:1.

Mass–Mass Calculations

Mass–mass calculations determine the mass of a product/reactant from a given mass of another substance using the following template:

• Template: grams of A → moles of A → moles of B → grams of B

• Equation:

• Example: How many grams of are produced from 4.0 g of ?

Chapter 5: Introduction to Solutions and Aqueous Solutions

Molarity Calculation

Molarity (M) is the concentration of a solution, defined as moles of solute per liter of solution.

• Equation:

• Example: 0.5 mol NaCl in 1.0 L solution:

Dilution Calculation

Dilution involves adding solvent to decrease the concentration of a solution. The amount of solute remains constant.

• Equation:

• Example: To make 250 mL of 0.1 M solution from 1.0 M stock:

Electrolytes vs Non-Electrolytes

Electrolytes conduct electricity in solution; non-electrolytes do not.

• Electrolytes: Substances that dissociate into ions (e.g., NaCl, HCl).

• Non-Electrolytes: Substances that do not form ions (e.g., sugar, ethanol).

Precipitation Reactions

Precipitation reactions form an insoluble product (precipitate) when two solutions are mixed. Solubility rules help predict if a precipitate forms.

• Key Point: Use a solubility chart to determine if products are soluble or insoluble.

• Example:

Complete Ionic and Net Ionic Equations

These equations show the actual forms of reactants and products in solution.

• Complete Ionic Equation: All strong electrolytes are shown as ions.

• Net Ionic Equation: Only species that change during the reaction are shown.

• Example: Complete: Net Ionic:

Acid-Base (Neutralization) Reactions

Acid-base reactions involve an acid and a base reacting to form water and a salt. They are called neutralization reactions because the acid and base neutralize each other.

• Key Point: The equivalence point is when moles of acid equal moles of base.

• Example:

Determining Oxidation States

Oxidation states (numbers) indicate the degree of oxidation of an atom in a compound. Rules are used to assign these numbers.

• Key Point: Elements in their standard state have oxidation number 0; oxygen is usually -2; hydrogen is +1 with nonmetals.

• Example: In , H is +1, O is -2.

Chapter 6: Gases

Boyle's Law

Boyle's Law describes the inverse relationship between pressure and volume at constant temperature for a fixed amount of gas.

• Equation:

• Relationship: As pressure increases, volume decreases (and vice versa).

Charles's Law

Charles's Law states that the volume of a gas is directly proportional to its temperature (in Kelvin) at constant pressure.

• Equation:

• Relationship: As temperature increases, volume increases.

Avogadro's Law

Avogadro's Law states that the volume of a gas is directly proportional to the number of moles at constant temperature and pressure.

• Equation:

• Relationship: More moles of gas mean greater volume.

Ideal Gas Law

The ideal gas law combines Boyle's, Charles's, and Avogadro's laws into one equation.

• Equation:

• Variables: P = pressure, V = volume, n = moles, R = gas constant, T = temperature (K)

Mole Fraction

Mole fraction is the ratio of moles of one component to the total moles in a mixture.

• Equation:

Molecular Speed vs. Molar Mass

The average speed of gas molecules is inversely related to the square root of their molar mass (Graham's law).

• Equation:

• Key Point: Lighter molecules move faster at the same temperature.

Effusion vs. Diffusion

Effusion and diffusion describe the movement of gas particles.

• Effusion: The process by which gas escapes through a small hole into a vacuum.

• Diffusion: The mixing of gases due to random molecular motion.

• Graham's Law of Effusion: