Unit 6: Stoichiometry

Introduction to Stoichiometry

• Stoichiometry is essentially algebra applied in the context of chemical reactions.
• It involves a process of plugging in values and following consistent steps.

Concept 1: Understanding the Mole

• The mole is a unit of measurement in chemistry, abbreviated as 'mol'.
• Used to measure large amounts of very small entities, such as atoms.
• One mole is equal to Avogadro's number, 6.022 x 10^{23} particles.
• Avogadro's number is the number of particles in one mole of a substance.

Importance of Moles

• Moles help convert between mass (grams) and number of particles (atoms/molecules).

Calculating with the Mole

• Example calculation: Convert moles to atoms using Avogadro's number.

Conversion Factors and Dimensional Analysis

• Similar to converting units in earlier chemistry concepts (e.g., kg to lbs).
• Use conversion factors to ensure units cancel out properly.

Significant Figures (Sig Figs)

• Important when rounding numbers during calculations.
• Number of sig figs should be consistent with measurements.

Practice Problems

• Convert moles to atoms and vice versa.
• Use a periodic table and a reference sheet for conversions.

Molar Mass

• Molar mass is measured in grams per mole.
• It tells the mass of one mole of a pure substance.
• Molar mass is numerically equal to atomic mass (from the periodic table).

Using Molar Mass in Calculations

• Conversion factors can be derived from molar masses.
• Practice converting between grams and moles.

Problem-Solving with Radar Method

• Read, Analyze, Diagnose, Assess, Reflect.
• Helps structure problem-solving in chemistry.

Calculating Molar Mass of Compounds

• Sum the atomic masses from the periodic table to find the molar mass.
• Find molar masses for compounds like H2O, NaCl, etc.

Conversion Factors for Compounds

• Use molar mass to convert between grams and moles for compounds.
• Practice problems included for better understanding.

Percent Composition

• Percentage by mass of each element in a compound.
• Calculated using the formula: (mass of element/molar mass of compound) x 100.
• Practice determining percent composition from given data.

Empirical and Molecular Formulas

• Empirical formula: Lowest whole-number ratio of atoms in a compound.
• Molecular formula: Actual number of atoms of each element in a compound.
• Steps to find empirical formulas from percentage composition.
• Conversion of empirical formula to molecular formula using given molar mass.

Practice Problems

• Use provided data to practice converting empirical formulas to molecular formulas using molar mass.

Encouragement for Students

• Emphasis on confidence and practice in mastering stoichiometry.
• Remember: Chemistry is problem-solving, and following structured steps helps.
• Seek help when needed and practice regularly.