Chemistry Basics: Key Concepts and Formulas

Posted on Aug 27, 2024 in Chemistry

Chemistry Basics

Fundamental Concepts

Chemical Reactions

Synthesis: A + B -> AB
Decomposition: AB -> A + B
Single Displacement: A + BC -> AC + B
Double Displacement: AB + CD -> AD + CB

Avogadro’s Number and Molecular Mass

Avogadro’s Number: 6.022 x 10²³
Molecular Mass: The number under the element symbol (amu)
Formula Mass: Sum of atomic masses of all elements in a compound
Molar Mass: Mass of one mole of a substance (grams)

Calculating Moles and Mass

Moles in grams: Divide grams by molar mass (amu)
Mass in grams: Multiply moles by molar mass (amu)
Number of molecules: Multiply moles by Avogadro’s number

Percent Yield

Percent Yield = (Actual Yield / Theoretical Yield) x 100

States of Matter and Solutions

Colloids and Solutions

Colloid: Solid particles suspended in a liquid (heterogeneous)
Solution: Solid particles dissolved in a liquid (homogeneous)
Mixture/Suspension: Particles settle at the bottom

Gas Laws

Boyle’s Law: P_iV_i = P_fV_f
Charles’s Law: V_i/T_i = V_f/T_f
Gay-Lussac’s Law: P_i/T_i = P_f/T_f
Combined Gas Law: P_iV_i/T_i = P_fV_f/T_f (Temperature in Kelvin)
Ideal Gas Law: PV = nRT (R = 0.0821 L.atm/K/mol)
Standard Temperature and Pressure (STP): 1 atm, 273 K (0°C)
Molar Volume at STP: 22.41 L/mol

Solubility

Saturated Solution: Holds the maximum amount of solute
Unsaturated Solution: Can hold more solute
Supersaturated Solution: Holds more solute than it theoretically should

Chemical Bonding and Oxidation Numbers

Types of Bonds

Ionic Bond: Transfer of electrons (metal + nonmetal)
Covalent Bond: Sharing of electrons (nonmetal + nonmetal)
Metallic Bond: Metal + metal

Oxidation Number Rules

Element: 0
Monatomic Ion: Equal to its charge
Compound: Sum of oxidation numbers is 0
Hydrogen: +1 (except in hydrides, -1)
Oxygen: -2 (except in peroxides, -1, and with fluorine, +2)
Polyatomic Ion: Sum of oxidation numbers equals the ion’s charge

Solubility Rules

Group I and ammonium compounds are soluble
Nitrates, acetates, and chlorates are soluble
Binary compounds of halogens (except F) with metals are soluble (except Ag, Hg(I), and Pb)
Sulfates are soluble (except Ba, Sr, Ca, Pb, Ag, and Hg(I))
Carbonates, hydroxides, oxides, silicates, and phosphates are insoluble (except for Rule 1)
Sulfides are insoluble (except for Ca, Ba, Sr, Mg, Na, K, and ammonium)

Acids, Bases, and pH

Acid-Base Theories

Arrhenius: Acids contain H+, bases contain OH-
Bronsted-Lowry: Acids are proton donors, bases are proton acceptors

pH and pOH

pH = -log[H+]
pOH = -log[OH-]
pH + pOH = 14

Radioactivity

Types of Decay

Alpha Decay: Loses 2 protons and 2 neutrons
Beta Decay: Gains 1 proton and loses 1 neutron
Gamma Decay: Releases energy as gamma rays (no change in element)

Penetration Power

Gamma > Beta > Alpha

Organic Chemistry

Alkanes, Alkenes, and Alkynes

-ane: Single bond
-ene: Double bond
-yne: Triple bond
meth (1), eth (2), prop (3), but (4), pent (5), hex (6), hept (7), oct (8), non (9), dec (10)

Chemistry Basics: Key Concepts and Formulas