Chemistry 151 Chapter 3 Flashcards

Moles and Mass Calculations

• Xenon (Xe) has a molar mass of 131.29 g/mol; 1.67 mol of Xe weighs approximately 219.25 g.
• Rubidium (Rb) has a molar mass of 85.47 g/mol; 2.21 g of Rb equals 0.026 mol.
• Chlorine (Cl) sample with 7.68×10²⁴ atoms can be converted to moles by dividing the number of atoms by Avogadro's number (6.022×10²³).
• Lead(II) chromate (PbCrO₄) has a molar mass of 323 g/mol, and 57.1 g corresponds to approximately 0.177 mol.
• Ethanol (C₂H₆O) has a molecular weight of 46.08 g/mol; a sample of 0.397 mol has a mass of 18.3 g.

Molecular Weight and Conversion

• Molecular weight of Ca₃(PO₄)₂ is calculated as 310.17 amu, factoring in contributions from calcium, phosphorus, and oxygen.
• To convert mass to moles, apply the formula: mass (g) x 1 mol/molar mass (g) = amount in mol.
• For molecule quantification: first convert grams to moles, then use Avogadro's number to find the total number of molecules.

Avogadro's Number and Moles

• Avogadro's number: 6.022 x 10²³ represents the number of atoms or molecules in one mole of a substance.
• One mole of any element has a mass in grams equal to its atomic weight; for example, 1 mol of carbon atoms equals 12.011 g.

Chemical Fundamentals

• Molecular mass is defined as the mass of one molecular compound in atomic mass units (amu).
• Atomic weight refers to the weighted average of an element's naturally occurring isotopes.
• Formula weight is the sum of the atomic weights in a formula unit, applicable to both molecular and ionic compounds.

Chemical Equations and Reactions

• A chemical equation describes reactants and products' identities and proportions in a reaction.
• Reactants are substances consumed during a chemical process, while products are formed post-reaction.
• Chemical formulas can represent a single molecule or numerous identical molecules.

Principles of Balancing Reactions

• Chemical equations must be balanced based on the law of mass conservation, ensuring equal numbers and kinds of atoms on both sides of the reaction.
• Example: Balancing CH₄ + O₂ produces CO₂ + H₂O can be represented as CH₄ + 2O₂ → CO₂ + 2H₂O.

Types of Reactions

• Different reaction types:
  • Combination reactions: A + B → C
  • Decomposition reactions: C → A + B
  • Combustion reactions: Involving rapid reactions that produce flames, usually with oxygen.

Miscellaneous Definitions

• Aqueous solution: Denoted as (aq).
• Gas: Denoted as (g).
• Liquid: Denoted as (l).
• Solid: Denoted as (s).
• Stoichiometry relates to mole ratios among reactants and products in chemical reactions.

Test your knowledge with these flashcards from Chemistry 151 Chapter 3. Focus on understanding the conversion of moles to grams using the molar mass of elements. Perfect for students looking to reinforce their grasp of fundamental chemistry concepts.