ChamrasCHEMISTRY 110 LECTURE NOTES

EXAM 3 Materials: Chp’s. 8, 9, 10, 11

Chapter 8Stoichiometry

*Remember: What’s in a chemical formula? (Chp. 7)

Example: N2O5

1. Types of elements:

2. Mole-to-mole ratios:

What’s in a balanced CHEMICAL EQUATION?

Example: 4Fe(s) + 3O2(g) 2Fe2O3(s)

Mole-to-mole ratios:

What is STOICHIOMETRY?

*Remember: What is a chemical reaction defined as, according to the Collision theory?

Draw the reaction shown in the equation above:

4Fe(s) + 3O2(g) 2Fe2O3(s)

Draw the reaction shown in the equation above:

Problem:

a) Given the equation for the production of iron(III)oxide, determine how many iron atoms would be needed for 3 molecules of oxygen gas:

b) Given the equation for the production of iron(III)oxide, determine how moles of iron would be needed for 3 moles of oxygen gas:

c) How many moles of rust are expected to be produced from the complete reaction of 12.0 moles of iron?

d) How many grams of oxygen are needed to react with 8.0 moles of iron?

e) How many milligrams of oxygen are needed to react with 67.7 grams of iron?

f) How many grams of rust are expected to be produced from the complete reaction of 32.2 grams of iron?

Stoichiometric Diagram

MOLE Is the Central Idea!

mass of A mass of B

molar mass molar mass of A of B mol:mol moles of A moles of B ratio

avogadro’s # avogadro’s #

particles of A particles of B

More problems:

Given the equation below:

2Cr(s) + 3Cl2(g) 2CrCl3(s)

a) How many formula units of chromium(III)chloride is expected to be produced from the complete reaction of 22.2 x 1045 atoms of chromium?

b) How many formula units of chromium(III)chloride is expected to be produced from the complete reaction of 22.2 x 1045 molecules of chlorine?

Limiting and Excess Reactants

Definitions:

Limiting Reactant:

Excess Reactant:

Example:

Chemical example:2Cr(s) + 3Cl2(g) 2CrCl3(s)

If 3 moles of chromium react with 4 moles of chlorine, determine the limiting reactant:

If 156.0 grams of chromium react with 284.0 grams of chlorine, determine the limiting reactant:

Another way of asking the same question: If 3 moles of chromium react with 4 moles of chlorine, determine the amount of

chromium(III)chloride EXPECTED to be produced:

If 156.0 grams of chromium react with 284.0 grams of chlorine, determine the amount of chromium(III)chloride EXPECTED to be produced:

Theoretical Yield

Actual Yield

Percent Yield

Equation:

Problem:a) If 3.332 grams of chlorine reacts with 1.11 grams of chromium, determine the theoretical yield of the product (how much of the product is expected to be produced?):

2Cr(s) + 3Cl2(g) 2CrCl3(s)

b) if the percent yield of chromium(III)chloride is determined to be 75.2, then determine the actual amount of it produced:

More Stoichiometric Examples:

Chapter 9Stoichiometry

A Brief Detour on the Development of the Periodic Table of Elements

In Ancient Chinese Philosophy: In Greek Philosophy:

Dmitri Mendeleev’s Original Periodic Table: (Based on Average Atomic Mass)

Modern Atomic Theory

Rutherford’s Atom: A theory developed to describe the structure of atoms, based on experimental evidence.

The Experiment:

Results:a)b)c)

Conclusion:

Electromagnetic Radiation : (AKA: Light)

Dual Nature:

Description: Electro – Magnetic

Properties:

Energy:

Frequency:

Wavelength:

Electromagnetic Radiation Spectrum: (A continuum)

Gamma X U.V. Visible I.R. -Wave R.F. Rays Rays Light

V B G Y O R

E E

Relationships: E,

Emission of Energy by Atoms: An Experiment.

Sample

Explanation:

Excited State

Energy

Ground State

One Last Detail:

Color of emitted light varies with varying sample.

Explanation:

Sample Line Spectrum

Further Insight To the Structure of Atom:

Energy

Quantum Chemistry:

Space is Quantized

Change of Electronic Energy with Changing Distance from Nucleus:

Atomic Orbitals:

Orbital Space

Definition:

Orbital Capacity:

How Is the Space Around the Nucleus Quantized?

Principal Energy Levels:

Orbital Types:

Electron & Orbital Arrangement Around the Nucleus:

Number Total Number

Nucleus of Orbitals of Electrons

n=1

n=2

n=3

n=4

Electron Configuration & Orbital Diagram:

H: He:

Li:

Na:

K:

Be:

Mg:

Ca:

Al:

N:

P:

O:

S:

Core Notation for Electron Configuration:

Blocks of the Periodic Table:

Types of Electrons:

a)

b)

Periodic Trends:

a) Electronegativity:

Definition:

Trend:

Three Most Electronegative Elements:

Electronegativity: ____ ____ ____

b) Atomic Size:

Trend:

c) Metallic Properties:

Examples of Metallic Properties:

Trend:

d) Ionization Energy:

Definition:

Trend:

Chapter 10Chemical Bonding

Review:Types of Chemical Bonds:

a)

b)

c)

Types of Chemical Compounds:

a)

b)

Bonding Spectrum:

100:0 Sharing 50:50 Sharing

Measurement of Bond Polarity:

Examples:

H Cl H H Cl Cl

Insight on the Charges of Different Ions:

Remember: Valence and Core Electrons

Electron Configurations:

He: Ne: Ar:

Na+:

Cl–:

Ca2+:

Main Objective in Bonding (Ionic or Covalent):

Examples:

Ionic Bonding:

Covalent Bonding:

Lewis Structure: A Drawing Tool

Elements:

Monatomic Ions:

Ionic Compounds:

Lewis Structures for Molecules

Steps:1. Determine the total number of valence electrons.2. Establish the basic structural connectivity.3. Fill in the remaining electrons.4. Check for the octet (duet) rule.

Bonding Electrons and Non-Bonding Electron Pairs (AKA: Lone Pairs)

Example:

Diatomic Examples:

Simple Examples:Choosing the central atom:

Question:***What if the Valence Electrons are Maxed Out & there are elements with an Unsatisfied Octet?

Multiple Bonds

Example: CO2

Example 2:

Question:What if there are two or more ways of drawing reasonable Lewis structures?

Resonance

Example: NO3–-

More Examples:

Molecular Geometry

Use VSEPR theory to draw the correct molecular geometry:

VSEPR Theory:

Examples:

a) No lone pair on the central atom:Example Molecular Geometry Bond

Angles

CO2:

BF3:

CH4:

b) 1 Lone pair on the central atom:Example Molecular Geometry Bond

Angles

O3:

NH3:

c) 2 Lone pairs on the central atom:Example Molecular Geometry Bond

Angles

H2O:

Chapter 11Gases

Remember: Some properties of gases…

Two ways to specify the amount of a sample of a gas:

a) moles (n)

Example:

b) pressure (P), volume (V), and temperature (T)

Example:

Pressure of Gases

Definition for pressure:

Equation for Pressure:

Units for Pressure

Conversions:

Atmospheric Pressure:

Temperature

Volume

Relationships between Pressure, Temperature, and Volume of Gasesa) Boyle’s Law: at Constant Temperature

Sample Problems:

1. If the pressure of a gas increases from 6.7 atm to 12,000. Torr, how does its volume change from an original value of 3.50 liters at constant temperature

2. If the volume of a gas is quadrupled, how does its pressure change?

b) Charles’s Law: at Constant Pressure

Sample Problems:

1. If the temperature of a gas changes from 100.0K to 100.0oC, determine the original volume of this gas if the final volume is 25.0 mL. Assume constant pressure.

2. If the temperature of a gas is doubled, how does its volume change at constant pressure?

c) Avogadro’s Law:

d) Combined Gas Law:

Sample Problems:

1. A sample of a gas has 4.50liters of volume, at 750.0mmHg and 220.0 oC. Calculate the new temperature of this sample if the pressure is decreased to 0.600 atm, and the volume is increased to 6.60 liters:

2. If the pressure of a gas is doubled and the volume is tripled, how does the temperature change?

e) Ideal Gas Law:

P . V = n . R . T

P =

V =

n =

R =

T =

Derivation:

Sample Problems:

1.

2.

STP

Molar Volume at STP

When to use:

Combined Gas Law:

Ideal Gas Law:

Molar Volume:Gas Stoichiometry

Given the P, V, and T of a gas involved in a chemical reaction, the n could be calculated.

Stiochiometric Diagram Revised & Improved:

mass of A mass of B

molar mass molar mass of A of B PV=nRT mol:mol PV=nRTVolume of moles of A moles of B Volume of A(g) ratio B(g)

avogadro’s # avogadro’s #

particles of A particles of B

Sample Stoichiometric Problem:

CaCO3(s) CaO(s) + CO2(g)

Quicklime, CaO, is produced by heating calcium carbonate, CaCO3. Calculate the volume of CO2 expected to be produced, at STP, from the complete decomposition of 152.0 grams of calcium carbonate.

Sample Problem 2:

CaCO3(s) CaO(s) + CO2(g)

Quicklime, CaO, is produced by heating calcium carbonate, CaCO3. Calculate the volume of CO2 expected to be produced, at 450.0K and 1200. mmHg, from the complete decomposition of 152.0 grams of calcium carbonate.