Lecture_13-Reaction_Stoichiometry

Lecture Overview

• Lecture 13: Focus on Stoichiometry

Upcoming Assignments (Page 2)

• Quiz 3: Due by 6 PM, Sunday, March 9

  • Covers material on intermolecular forces, empirical/molecular formulas, and reaction stoichiometry

  • 60 minutes duration, open notes, 2 attempts per question

  • Important to complete HW7 before taking Quiz 3

• Quiz 4: Due by 8 AM, Thursday, March 27

• OWL HW7: Due by 8 AM, Tuesday, March 11

Chemical Reactions (Page 3)

• Definition: Reorganization of reactant molecules to form product molecules

• Process: Involves breaking existing bonds and forming new ones

• State Notation:

  • (g): gas

  • (l): liquid

  • (s): solid

  • (aq): aqueous, indicates reaction occurs in water

• Law of Conservation of Mass: Atoms are conserved; reactions must be balanced

Chemical Reactions Continued (Page 4)

• Mole Relationships: Mole ratios between reactants and products

• Diatomic Elements: Some nonmetals exist as diatomic molecules in nature (e.g., H2, N2, O2, etc.)

Types of Chemical Reactions (Page 5)

• Synthesis: Two or more reactants produce one product

  • Example: 2 H2(g) + O2(g) → 2 H2O(l)

• Decomposition: One reactant produces two or more products

  • Example: (NH4)2Cr2O7(s) → Cr2O3(s) + N2(g) + 4 H2O(g)

• Single Displacement: An element replaces another element in a compound

  • Example: Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq)

• Double Displacement: Two ions exchange partners

  • Example: 2 AgNO3(aq) + Na2CO3(aq) → Ag2CO3(s) + 2 NaNO3(aq)

• Combustion: Substance reacts with oxygen gas

  • Example: 2 CH3OH(l) + 3 O2(g) → 2 CO2(g) + 4 H2O(l)

Balancing Practice (Page 6)

• Practice balancing:

  • NH3(g) synthesis reaction

  • H2O2(aq) decomposition

  • thermite reaction (Al and Fe3O4)

  • gasoline (C8H18) combustion reaction

Clicker Question 1 (Page 7-8)

• Balanced chemical reactions imply:

  • a. Numbers of molecules are conserved in chemical change

  • b. Numbers of atoms are conserved in chemical change

  • c. Mass is conserved in chemical change

  • d. Both b and c are correct

  • e. All answers are correct

"Perfect" Chemical Reaction (Page 9-10)

• Balanced Equation: 4 A2 + 8 AB → 8 A2B

• A2 + 2 AB → 2 A2B

• Limiting Reactant: Reactant that runs out first

Clicker Question 2 (Page 12-13)

• Synthesis Reaction: 9 H2 + 5 N2 → NH3

• Total Molecules Present After Completion:

  • Options: a. 6, b. 8, c. 10, d. 12, e. 14

Real Chemical Reaction (Page 14)

• Example: 3 H2(g) + N2(g) → 2 NH3(g)

Stoichiometry Questions (Page 15, 17, 18, 23-24)

• Stoichiometry Question 1:

  • Reaction: 8 Al(s) + 3 Fe3O4(s) → 4 Al2O3(s) + 9 Fe(s)

  • If 10.0 g of Fe3O4 reacted, produce: 5.87 g Al2O3

• Stoichiometry Question 2:

  • If 9.45 g of Al2O3 is produced, how much Al reacted? Result: 5.00 g Al

• Stoichiometry Question 3:

  • Reaction with 10.0 g Fe3O4 and 5.00 g Al produced: 5.87 g Al2O3

• Stoichiometry Question 4:

  • When 10.0 g Fe3O4 reacted with 5.00 g Al, leftover: 0 g Fe3O4, 1.89 g Al excess

Clicker Question 3 (Page 24-25)

• Complete the sentence: "The limiting reactant in a reaction:"

  • a. Smallest gram present

  • b. Smallest coefficient in the balanced equation

  • c. Smaller molar mass

  • d. Smallest number of moles present

  • e. None of the above

Stoichiometry Question 5 (Page 26-28)

• Reaction: 8 Al(s) + 3 Fe3O4(s) → 4 Al2O3(s) + 9 Fe(s)

• If 4.62 g Al2O3 is produced, calculate percent yield from the amounts in question 3.