Learn about the mole and its significance in chemistry
How to convert between grams, moles, and number of particles
Important Units in Chemistry
The Mole
Definition: A unit for amount of substance in the International System of Units
Reference: Number of atoms in a 12-gram sample of pure Carbon-12
Analogy: Similar to terms like "dozen" (e.g., a dozen of donuts or eggs)
Avogadro's Number
Value: 6.022 x 10^23
Named After: Amedeo Avogadro
Significance: One mole of any substance contains 6.022 x 10^23 particles
Molar Mass
Definition: Mass in grams of one mole of a substance
Unit: Grams per mole
Relation to Atomic Mass: Numerically equivalent to atomic mass in atomic mass units (amu)
Calculation Techniques
Conversion between number of particles and moles: Use Avogadro's number
Conversion between moles and mass: Use molar mass
Example Problems
Example 1: Potassium Requirement
Problem: Convert dietary potassium (4.7 grams) to moles
Solution Process:
Identify given mass of potassium
Calculate moles using molar mass
Conversion: Mass (grams) / Molar Mass (grams/mole)
Result: 0.12 moles of potassium
Example 2: Mass of Argon in Air
Problem: Convert 9.2 x 10^(-4) moles of argon to grams
Solution Process:
Identify given moles of argon
Calculate mass using molar mass
Conversion: Moles x Molar Mass (grams/mole)
Result: 0.037 grams of argon
Example 3: Copper Atoms in Wire
Problem: Number of copper atoms in 5 grams of copper wire
Solution Process:
Start with given mass
Convert grams to moles using molar mass
Convert moles to atoms using Avogadro's number
Result: 4.74 x 10^22 atoms of copper
Example 4: Glycine Molecules
Problem: Moles of glycine in 28.35 grams
Solution Process:
Calculate molar mass from molecular formula: C2H5O2N
Use periodic table for atomic masses to calculate total molar mass
Convert grams to moles using calculated molar mass
Result: 0.378 moles of glycine
Additional Resources
Textbook problems for further practice on these calculations
Study Tips: Focus on understanding how to set up the conversion factors correctly and ensuring units cancel correctly to achieve desired unit in result.