Mole and Equivalent Concept Formulas for Chemistry

Posted on Dec 27, 2025 in Civil Engineering

Mole and Equivalent Concept Cheat-Sheet

1. Basic Measurements

  • Density (ρ): ( ρ = \frac{\text{mass}}{\text{volume}} )
    • Mass: ( \text{mass} = ρ \times \text{volume} )
    • Volume: ( \text{volume} = \frac{\text{mass}}{ρ} )
    • SI Unit: ( \text{kg/m}^3 )

2. Mole Concept and Avogadro’s Number

  • Number of Moles (n): ( n = \frac{\text{mass}}{\text{molar mass}} )
    • Molar Mass: ( \text{molar mass} = \frac{\text{mass}}{n} )
    • Mass from Number of Particles: ( \text{mass} = \left( \frac{\text{Number of particles}}{N_A} \right) \times \text{molar mass} )
    • Number of Moles (Gases at STP): ( n = \frac{\text{volume at STP}}{22.4 \text{ L}} )
  • Number of Particles: ( \text{Number of particles} = n \times N_A ), where ( N_A = 6.022 \times 10^{23} )
    • Avogadro’s Law: ( V \propto n ) (at constant T and P)

3. Laws of Chemical Combination

  • Law of Conservation of Mass: ( \text{Mass of reactants} = \text{Mass of products} )
    • Mass Ratio from Stoichiometry: ( \text{Mass of A} : \text{Mass of B} = (\text{Coefficient of A} \times \text{Molar mass of A}) : (\text{Coefficient of B} \times \text{Molar mass of B}) )
  • Law of Constant Proportions: The mass ratio of elements in a compound is constant.
  • Law of Multiple Proportions: The ratio of masses of one element combining with a fixed mass of another is a simple whole number ratio.
  • Law of Reciprocal Proportions: The ratio of masses of two elements combining with a third element is the same as the ratio when they combine with each other.
    • Mass Ratio: As defined above.
  • Gay-Lussac’s Law: The volume ratio of gases is a simple whole number ratio.
    • Volume Ratio to Mole Ratio: ( \text{Volume ratio} = \text{Mole ratio} )

4. Stoichiometry and Limiting Reagent

  • Mole Ratio: ( \frac{\text{Moles of A}}{\text{Moles of B}} = \frac{\text{Coefficient of A}}{\text{Coefficient of B}} )
    • Moles of Product: ( \text{Moles of product} = \text{Moles of limiting reagent} \times \frac{\text{Coefficient of product}}{\text{Coefficient of limiting reagent}} )
    • Mass of Product: ( \text{Mass of product} = (\text{Moles of product}) \times (\text{Molar mass of product}) )
  • Limiting Reagent: ( \text{Limiting reagent} = \text{Reactant with the least moles relative to stoichiometric ratio} )
    • Excess Reagent: ( \text{Moles of excess reagent remaining} = \text{Initial moles} – \text{Moles consumed} )

5. Percent Yield

  • Percent Yield: ( \text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100 )
    • Theoretical Yield: ( \text{Theoretical Yield} = (\text{Moles of limiting reagent}) \times \left( \frac{\text{Coefficient of product}}{\text{Coefficient of limiting reagent}} \right) \times (\text{Molar mass of product}) )
    • Actual Yield: ( \text{Actual Yield} = \frac{\text{Percent Yield}}{100} \times \text{Theoretical Yield} )
    • Percent Efficiency: ( \text{Percent Efficiency} = \text{Percent Yield} )

6. Concentration Terms

  • Molarity (M): ( M = \frac{\text{moles of solute}}{\text{volume of solution (L)}} )
    • Molarity to Molality: ( m = \frac{M \times 1000}{(\text{mass of solvent in g}) \times (1000 – M \times \text{molar mass of solute})} )
  • Molality (m): ( m = \frac{\text{moles of solute}}{\text{mass of solvent (kg)}} )
    • Mole Fraction to Molality: ( m = \frac{X_{\text{solute}} \times 1000}{(1 – X_{\text{solute}}) \times M_{\text{solvent}}} )
  • Mole Fraction (X): ( X_A = \frac{\text{moles of A}}{\text{total moles}} )
  • Mass Percent: ( \text{Mass %} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100 )
  • PPM (Parts Per Million): ( \text{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6 )
  • Volume Percent: ( \text{Volume %} = \frac{\text{volume of solute}}{\text{volume of solution}} \times 100 )

7. Equivalent Concept

  • Equivalent Mass (E): ( E = \frac{\text{Molecular mass}}{\text{Valency Factor}} )
    • Equivalent Mass of Acids: ( E = \frac{\text{Molecular mass}}{\text{Basicity}} )
    • Equivalent Mass of Bases: ( E = \frac{\text{Molecular mass}}{\text{Acidity}} )
  • Valency Factor (Z): ( Z = \text{Number of H}^+ \text{ or OH}^- \text{ ions per molecule (for acids/bases)} )
  • Normality (N): ( N = \frac{\text{equivalents of solute}}{\text{volume of solution (L)}} )
    • Equivalents: ( \text{Equivalents} = \frac{\text{mass}}{\text{equivalent mass}} )
    • Normality-Molarity Relationship: ( N = M \times Z )
  • Law of Chemical Equivalence: ( \text{Equivalents of reactant} = \text{Equivalents of product} )

8. Dilution Law

  • Dilution Law (Molarity): ( M_1 V_1 = M_2 V_2 )
    • Final Molarity: ( M_2 = \frac{M_1 V_1}{V_2} )
    • Moles Before and After: ( \text{Moles before} = \text{Moles after} )
  • Dilution Law (Normality): ( N_1 V_1 = N_2 V_2 )
    • Final Normality: ( N_2 = \frac{N_1 V_1}{V_2} )