Essential Chemistry Formulas and Molecular Geometry Reference

Essential Chemistry Formulas and Reference

Miscellaneous Formulas

• Area of a Circle: 3.14r²
• Volume: Area × Height
• Density: Mass / Volume
• % Composition of Element: [(# of atoms of element) × (atomic weight of element)] / formula weight of substance × 100
• Molarity: (moles of solute) / (volume of solution in Liters)
• Bond Order: (# shared electrons) - (# nonbonding electrons) / 2
• Pressure: Force / Area
• Pressure × Volume: nRT
• Density of Gas: (Pressure × Molar Mass) / (R × Temperature)
• Molarity of Gas: (Density × R × Temperature) / Pressure

Temperature and Chemical Conversions

• Celsius to Kelvin: K = C + 273.15
• Kelvin to Celsius: C = K - 273.15
• Celsius to Fahrenheit: F = 9/5(C) + 32
• Fahrenheit to Celsius: C = 5/9(F - 32)
• 1 amu: 1.66054 × 10⁻²⁴ g
• Grams to Moles: Divide by formula weight
• Moles to Grams: Multiply by formula weight
• Moles to Molecules: Multiply by 6.022 × 10²³
• Molecules to Moles: Divide by 6.022 × 10²³
• Pressure: 1 atm = 760 torr

Molecular Shapes and Steric Numbers

Steric # = (# of bonds) + (nonbonding electron pairs)

Strong Acids and Bases

Energy and Thermodynamics

• Kinetic Energy (Ek): 1/2mv²
• Potential Energy (Eel): (kQ₁Q₂)/d
• Work: Force × distance or -Pressure × ΔVolume
• Internal Energy: E(final) - E(initial)
• Enthalpy (H): Internal energy + (pressure × volume)
• Enthalpy of Reaction: H(products) - H(reactants)
• Specific Heat: (heat transferred) / (mass × Δtemp)
• Change in Enthalpy: m × s × ΔT
• Lattice Energy: K [(Q₁Q₂) / d]

pH Calculations

pH = -log₁₀[H⁺]

[H⁺] = 10⁻ᵖᴴ

Example: pH = -log₁₀(1.4 × 10⁻⁵) = 4.85