1.1 (Filled-in Slideshow) Balancing Equations
Balancing Equations Unit 2: SCH3U/4C
Page 1: Introduction
Overview of balancing equations in chemistry related to the SCH3U/4C curriculum.
Page 2: Counting Atoms - More Practice
Task: Determine the number of atoms in various compounds.
Example: 2 + 7 + 5 + b + 5 + b + 5 (possibly referring to different compounds).
Expression shown implies counting total atom types based on the variable representations.
Page 3: What is a Chemical Reaction?
Definition: Processes in which substances (reactants) interact to form new substances (products).
Reactants: Substances before the reaction.
Products: Substances formed after the reaction.
Page 4: Representing Chemical Reactions (Grade 11 Only)
Learning Objective: Ability to represent chemical reactions in three ways:
Word Equation
Example: Iron + Oxygen → Iron(III) oxide.
Page 5: Representing Chemical Reactions - Skeleton Equation (Grade 11 Only)
Skeleton Equation: Includes chemical formulas and physical state of elements/compounds.
Example: Fe(s) + O2(g) → Fe2O3(s)
States:
(s): solid
(l): liquid
(g): gas
(aq): aqueous.
Page 6: Representing Chemical Reactions - Balanced Equation (Grade 11 Only)
Balanced Equation: Shows the number of each type of molecule involved.
Example: 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)
Page 7: Law of Conservation of Mass
Concept: Mass cannot be created or destroyed in a chemical reaction.
Cannot lose or gain atoms during reactions.
Mass of reactants must equal mass of products.
Atoms can only be rearranged.
Page 8: Rules for Balancing Equations
Place a line in front of each molecule to easily visualize.
Coefficients: Only numbers can be placed here, indicating the amount of each molecule.
Example: CO2 + H2O → H2CO3.
Page 9: Rules for Balancing Equations - Impact of Coefficients
A coefficient multiplies the number of atoms in a molecule.
Example: 2 H2O → 4 H + 2 O (shows effect of coefficient in splitting molecules).
Page 10: Rules for Balancing Equations - Coefficient Effects
A coefficient affects only the immediate molecule after it.
Example: 2 H2O + CO2 →
Here, 2 only applies to H2O, not CO2.
Page 11: Rules for Balancing Equations - Polyatomic Ions
If a polyatomic ion appears on both sides of the reaction, treat it as a package.
Example: NH4NO3 → uses 1 nitrate ion instead of balancing each separate atom.
Page 12: Balancing Practice
Example: 2 Na(s) + Cl2(g) → 2 NaCl(s)
Balanced as Left Side (LS) = Right Side (RS)
Confirming equation balance of Reactants and Products.
Page 13: Practice 2
Example: 2 Ag + NO2 → 2 AgNO2.
Ensure the total count of each atom from reaction is maintained.
Page 14: Practice 3
Example: NH4(g) + 2 O2(g) → 2 H2O(l) + NO2(g)
Where total counts of Nitrogen, Hydrogen, and Oxygen atoms must match in balancing.