Chemistry: Oxidation and Reduction Concepts

Warm-Up 11/11 - 11/12

• Sucrose is a covalent molecule
• Sucrose is likely soluble in water due to its polar structure.
• Sucrose likely has a large number of hydroxyl groups (-OH) creating dipole-dipole interactions with water.

Mols, Stoich and Thermo

• Units Covered: S1.4, R2.1, R1.1-1.3
• Topics to review: moles, molecular/empirical formulae, stoichiometry, and thermochemistry

From now 'till 2025

• Review moles, molecular/empirical formulae
• Review stoichiometry
• Review thermochemistry (R1.1-R1.3)

S1.4 - Counting Particles - The Mole

• The mole (mol) is the SI unit of amount of substance
• One mole of an entity contains 6.02 x 10²³ of that entity

Mols - Example problem

• If you have 2 mols of water molecules:
  • You will have 2 mols of oxygen atoms.
  • You will have 4 mols of hydrogen atoms.

Why moles?

• Chemical reactions occur proportionally
• Coefficients in a chemical reaction represent the ratio of moles of reactants and products

An aside - atomic masses

• Relative atomic mass (A_r) is the weighted mean of the naturally occurring isotopes
• Relative atomic mass has no units; it is a ratio
• Actual atomic mass is measured in grams per mole

Molar masses

• Molar mass is the mass of one mole of a substance
• Molar mass is given the symbol M and has units of g/mol
• Example: Molar mass of helium is 4.00 g/mol

Example problem

• If you have one mole of water:
  • You will have 16.00 g of oxygen
  • You will have 2.02 g of hydrogen

Molar masses

• For covalent molecules, use molecular mass
• For ionic compounds, use formula mass
• This information is found in the data booklet

Recall dimensional analysis

• Dimensional analysis is a technique for converting units
• To use it, first identify your givens and your goal
• Then identify the conversion factors that will help you convert to your goal

Dimensional analysis time

• Convert 10 grams of water to moles using molar mass

Practice - deduce the amount/mass of different substances

• Deduce the amount of ammonia (in moles) for a given mass of ammonia and/or a given number of ammonia molecules
• Deduce the mass of calcium carbonate for a given number of moles
• Deduce mass of hydrogen for a given number of atoms

Empirical formula

• The empirical formula represents the simplest whole number ratio of atoms in a molecule
• It can be calculated from masses of the elements or percentage composition by mass.

Empirical formula tips

• The empirical formula shows the simplest whole number ratio of atoms in a substance
• The percentage of each element can be used to calculate the empirical formula
• You can assume 100 grams of substance to simplify the calculation

Emp. example prob

• A hydrocarbon contains 85.7% by mass of carbon. Calculate the empirical formula

Molecular formula

• The molecular formula shows the actual number of atoms of each element in a compound
• It can be determined from the empirical formula and the molar mass of the molecule

More molecular formula practice

• Determine the molecular formula of a compound, given the empirical formula and the relative molecular mass

"Mol airlines"

• Identify chemicals quickly
• Write a one sentence 'report' for each chemical
• Complete this on the back of the paper.

Mols

• There are more atoms in a small amount of sugar than there are stars in the universe

Mol of sugar vs EVERY STAR IN THE SKY

• Sugar has a much higher number of atoms per structure than the number of stars in the universe
• The molecular formula for sugar is C₁,₂H₂₂O₁₁

"All the stars in the sky are our enemy"

• A mole of sugar contains 135 times more atoms than the number of stars in the universe

R2.1 - Stoichiometry

• Stoichiometry is the study of the numerical relationships between reactants and products in a balanced chemical reaction.
• Stoichiometric calculations involve moles.
• Mass to mass problems, moles to moles problems, and moles to mass are possible

Stoich Problems - Mol to Mol / Mass to Mol

• If you have a certain number of moles of one substance, the ratio of moles of reactants and products can be used to determine the moles of another substance

Stoich Problems - Mol to Mass / Mass to Mass

• If you have a certain number of grams of one substance, you can use the molar mass and mole ratios of reactants and products to determine the moles/mass of another substance

Limiting Reagents - Burger...

• Limiting reagents describe a situation when one reactant is used up first in a reaction.
• Determine the maximum number of cheeseburgers that can be made with a given amount of patties, buns, and cheese

Limiting Reagent / Limiting Reactant

• The limiting reagent is determined by finding the theoretical yield of the reactant that produces the smallest number of moles of products
• Determine which reactant will be used up first
• The limiting reagent limits the amount of product that can be formed

Worked example

• Calculate the amount (in moles) of sodium chloride produced when a specific amount of sodium reacts with chlorine

Limiting Reagent Problems

• P₄ + 6Cl₂ → 4PCl₃. Determine the amount of PCl₃

Warm-Up on whiteboard

• This refers to a given warm-up activity for the class

Theoretical vs Experimental Yield

• Theoretical yield is the maximum amount of product possible
• Experimental yield is the amount of product obtained in a reaction

Example

• Given an experimental yield and a theoretical yield, determine the percentage yield

Bromine reacts with ethene to form 1,2-dibromoethane

• In a given reaction, calculate the percentage yield of a compound

Atom Economy

• Atom economy is a measure of how many atoms of the desired product are produced in a chemical reaction
• Atom economy takes into account the waste produced in reactions
• Calculate the atom economy for a specific reaction

Task 1

• Identify the compounds produced in a given reaction of chlorine gas and ethene
• Use data to calculate the atom economy
• Determine maximum theoretical yield of the product given the mass of reactants
• Determine the percentage yield of the product given the experimental yield

Concentration

• A molar solution (M or mol/L) is a solution of one mole of solute dissolved in one liter of solution
• Concentration is measured in moles per liter or moles per cubic decimeter

Practice - Calculate the mass/concentration of substances in a solution

• Calculate mass of sodium hydroxide present in a given solution
• Calculate the concentration of the solution from the mass of a chemical compound

Ionic Equations

• In a double replacement reaction where a precipitate (solid) forms, the net ionic equation is the overall equation that only includes the ions that participate in the reaction.
• Spectator ions are the ions that do not participate in the reaction.

Half Reactions

• Oxidation is the loss of electrons
• Reduction is the gain of electrons

Standard Temperature and Pressure (STP)

• STP is defined as a temperature of 273.15 K and a pressure of 100 kPa
• Used for gas calculations and gas stoichiometry

Post Thanksgiving Break Warm-Up

• Given a balanced chemical equation, initial mass of substance, and a given number of moles of a second substance, calculate the mass of the product

Reminder of the ideal gas law

• Ideal gas law describes the gas law PV=nRT, which relates pressure, volume, number of moles, and absolute temperature of a gas
• The ideal gas constant (R) is useful for stoichiometry reactions involving gases

Complete Combustion

• Complete combustion involves a hydrocarbon reacting with oxygen to form carbon dioxide and water.
• Complete combustion is used in many industrial processes

Ex: Complete Combustion

• Write a balanced chemical equation for complete combustion of different compounds

Multiple Choice Work Time

• Skip some practice questions for multiple choice

R1.3 - Intro

• This unit deals with thermodynamics
• Chemical reactions involve energy changes

Combustion of metals

• When a metal reacts with oxygen, metal oxides are produced, which can be basic

Combustion of non-metals

• Some nonmetal combustion reactions produce acid rain
• Combustion reactions create various oxides

Complete Combustion of Hydrocarbons/Alcohols

• Complete combustion reactions produce carbon dioxide and water
• Fuels (alkanes and alcohols) are hydrocarbons

Practice - Write equations for complete combustions

• Write equations describing complete combustion reactions for given chemical compounds

Incomplete combustion of hydrocarbons

• Incomplete combustion reactions form carbon monoxide (often a pollutant) or solid carbon

• Incomplete combustion reactions are less exothermic than complete combustion

  Practice - Write equations for incomplete combustions

• Write equations for incomplete combustions for given chemical compounds

Why is oil still the dominant fuel?

• Oil has higher specific energy than other sources

• Logistical factors make it easier to use oil than other energy sources.

  Specific Energy

• Calculate specific energy using dimensional analysis and the molar mass of the compound

Specific Energy Implication

• Octane has a greater specific energy than ethanol
• This means releasing energy from equal masses of octane and ethanol, octane releases more energy

Energy density

• Enthalpy of combustion measures energy released per mole of a substance during combustion
• Specific energy measures energy released per unit mass during combustion
• Energy density measures energy released per unit volume during combustion

Fossil Fuels

• Fossil fuels are coal, crude oil, and natural gas
• Natural gas is mostly methane
• Crude oil is a mixture of hydrocarbons
• Different coal types have varying carbon percentages and specific energy values

Fossil fuel - Advantages / Disadvantages

• Fossil Fuels are compared in terms of advantages and disadvantages

Intro to Fuel Cells

• Fuel cells convert chemical energy to electrical energy

1/15 - 1/16 Warm-Ups

• Write the incomplete combustion equation for propane
• Using section 12 in the data booklet, calculate the enthalpy of a reaction for the given reactants and products, and calculate percentage error

Brief, Post-Break, R1.1 Review

• Temperature measures the average kinetic energy of molecules
• Heat is a form of energy

Standard Enthalpy Changes

• The enthalpy change is measured at standard conditions (298 K and 100 kPa)
• By convention, standard enthalpy changes are given the symbol ΔH°

Calorimetry

• Calorimetry is a technique that measures changes in heat flow during chemical and physical processes
• Specific heat capacity of water is 4.18 kJ/kg•K

Specific Heat Practice

• Calculate the amount of energy needed to heat up a quantity of water
• Calculate the final temperature of iron when the same amount of energy is added

Calorimetry - "Coffee Cup" Style

• Coffee cup calorimetry measures the heat released or absorbed in a chemical reaction in solution

Calorimetry - "Bomb" Style

• Bomb calorimetry measures energy changes in combustion

The standard enthalpy change of combustion

• Determine the mass of a given chemical that would increase a given mass of water's temperature by a specific amount

1.1 MC Practice

• Solve multiple-choice questions about chemical reactions and enthalpy changes

1/17 - 1/22 Warm Up

• Calculate the temperature change when a given volume of propane is ignited in a bomb calorimeter, and a given amount of water is present.

Test your knowledge of oxidation and reduction principles, including the acronym OILRIG and various half-reactions. This quiz covers concepts related to combustion, reactions of hydrocarbons, and the products formed in chemical reactions. Ideal for chemistry students looking to enhance their understanding.