Stoichiometry and Concentration Formulas

Fundamental Stoichiometry Formulas

Number of Moles (N)

• Formula: ( N = \frac{\text{mass in grams}}{\text{molar mass in grams/mole}} )
• Units: Grams (g), grams per mole (g/mol), moles

Variations

• Mass Calculation: ( \text{mass} = \text{moles} \times \text{molecular weight} )
• Molar Mass Calculation: ( \text{molar mass} = \frac{\text{mass}}{\text{moles}} )

Avogadro's Number

• Definition: 1 mole = ( 6.02 \times 10^{23} ) (like a dozen = 12)

Percentage Calculations

Percent Composition

• Formula: ( \text{Percent Composition} = \frac{\text{mass of element}}{\text{total mass of compound}} \times 100% )

Percent Yield

• Formula: ( \text{Percent Yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100% )

Percent Error

• Formula: ( \text{Percent Error} = \frac{\text{measured value} - \text{actual value}}{\text{actual value}} \times 100% )
• Absolute Error: Difference between measured value and actual value

Concentration Formulas

Molarity (M)

• Formula: ( M = \frac{\text{moles of solute}}{\text{volume of solution}} )
• Units: Moles (mol), Volume (L)
• Variations:
  • Moles: ( \text{moles} = M \times V )
  • Volume: ( V = \frac{\text{moles}}{M} )

Solute, Solvent, and Solution

• Solute: Substance dissolved (e.g., NaCl)
• Solvent: Substance that dissolves the solute (e.g., water)
• Solution: Mixture of solute and solvent

Dilution Equation

• Formula: ( M_1V_1 = M_2V_2 )
  • Example: Increasing volume decreases concentration
  • Explanation: Moles stay constant during dilution

Additional Resources

• Videos and printouts available via links provided in the lecture description for more examples and a formula sheet.