1.3 Quantitative Relationships in Chemistry

Stoichiometry is the math behind chemical reactions. It uses the mole concept to connect the microscopic world of atoms with measurable quantities in the lab. Understanding moles and molar mass is key to predicting reaction outcomes and calculating product yields.

Balancing equations and identifying limiting reactants are crucial skills in stoichiometry. These concepts allow chemists to determine the maximum amount of product possible and calculate percent yields. Mastering these fundamentals opens doors to more complex chemical calculations and analysis.

Fundamental Concepts in Stoichiometry

Mole concept in stoichiometry

Top images from around the web for Mole concept in stoichiometry

• 

  Reaction Stoichiometry | Boundless Chemistry View original

  Is this image relevant?

• 

  Formula Mass and the Mole Concept | Chemistry: Atoms First View original

  Is this image relevant?

• 

  ACTIVITY 3: IMAGES AND VIDEO | MOLE CONCEPT View original

  Is this image relevant?

• 

  Reaction Stoichiometry | Boundless Chemistry View original

  Is this image relevant?

• 

  Formula Mass and the Mole Concept | Chemistry: Atoms First View original

  Is this image relevant?

1 of 3

Top images from around the web for Mole concept in stoichiometry

• 

  Reaction Stoichiometry | Boundless Chemistry View original

  Is this image relevant?

• 

  Formula Mass and the Mole Concept | Chemistry: Atoms First View original

  Is this image relevant?

• 

  ACTIVITY 3: IMAGES AND VIDEO | MOLE CONCEPT View original

  Is this image relevant?

• 

  Reaction Stoichiometry | Boundless Chemistry View original

  Is this image relevant?

• 

  Formula Mass and the Mole Concept | Chemistry: Atoms First View original

  Is this image relevant?

1 of 3

• Mole quantifies $6.022 \times 10^{23}$ particles (atoms, molecules, ions)
• Standard unit measures amount of substance in chemical reactions
• Bridges macroscopic quantities with atomic-scale entities for accurate calculations
• Mole ratios in balanced equations represent relative amounts of reactants and products
• Coefficients in equations indicate mole quantities, predict reaction outcomes (2H₂ + O₂ → 2H₂O)

Conversions with molar mass

• Molar mass sums atomic masses of all atoms in molecule (H₂O: 18.015 g/mol)
• Mass to moles: divide mass by molar mass (36.03 g H₂O / 18.015 g/mol = 2 mol H₂O)
• Moles to mass: multiply moles by molar mass (2 mol H₂O × 18.015 g/mol = 36.03 g H₂O)
• Moles to particles: multiply by Avogadro's number (2 mol H₂O × $6.022 \times 10^{23}$ = $1.2044 \times 10^{24}$ molecules)
• Particles to moles: divide by Avogadro's number ($1.2044 \times 10^{24}$ molecules / $6.022 \times 10^{23}$ = 2 mol H₂O)
• Dimensional analysis uses conversion factors, cancels units for accurate problem-solving

Chemical Reactions and Stoichiometry

Balancing and stoichiometric calculations

• Balance equations by adjusting coefficients, conserve mass and atoms (2H₂ + O₂ → 2H₂O)
• Use balanced equations to determine quantities of reactants or products
• Mole-to-mole calculations directly use coefficients (2 mol H₂ reacts with 1 mol O₂)
• Mass-to-mass calculations convert masses to moles, then use coefficients
• Gas volume calculations use molar volume at STP (22.4 L/mol)
• Percent yield compares actual to theoretical yield: $(actual yield / theoretical yield) \times 100\%$

Limiting reactants and theoretical yield

• Limiting reactant completely consumed, determines product amount (5 mol H₂ + 3 mol O₂ → H₂O, O₂ limits)
• Excess reactant remains after reaction completion (H₂ in above example)
• Identify limiting reactant by comparing mole ratios to equation coefficients
• Calculate theoretical yield based on limiting reactant using stoichiometric ratios
• Percent excess quantifies unused reactant: $((moles excess - moles required) / moles required) \times 100\%$