Chapter+10-The+Mole

= Chapter 10: MOLE =
 * Pj Hamill (287-288) **
 * Brandon Boisclair (289-291) **
 * Olivia Richardson (292) **
 * Nate Lynch (293) CO-editor **
 * Alex Nunan (294) **
 * Dakota Pimentel (295-296) **

Measuring Matter - Key Vocab - People often measure the amount of something by one of three methods-by count, by mass, or by volume. ' A unit of measurement, a mole of a substance is 6.02 x 10^23
 * PJ HAMILL (287-288) **
 * Mole
 * Avogadro's Number
 * Representative Particle
 * Molar Mass
 * Brandon Boisclair (289-291) **
 * What is a Mole? **

This number was developed byy Avogadro and is now known as Avogadro's Number. - He helped clarify the difference between atoms and molecules.


 * REPRESENTATIVE PARTICLE** - refers to the species present in a substance: usually atoms, molecules, or formula units.


 * CONVERSION:**

moles= representative particles X __. 1 mole__ 6.02 x 10^23 representative particles

Olivia Richardson (292)
__ Converting Moles to Number of Atoms and Particles __ Sample Problem:
 * Propane is a gas used for cooking and heating. How many atoms are in 2.12 mol of propane? (C3H8)?
 * This problem is a mole conversion problem where we will have to use Avogadro's Number which is 6.02 X 10^23
 * There will be two conversion factors in the problem. The first is 6.02 X 10^23 molecules of C3H8 / 1 mol C3H8 The next conversion factor will be 11 atoms / 1 molecule C3H8. The destination of the problem is atoms and the starting point is 2.12 mol C3H8.
 * This is what the problem should look like all set up: atoms=2.12 mol C3H8 X 6.02 x 10^23 molecules C3H8 / 1 mol C3H8 X 11 atoms / 1 molecule
 * After the process of dimensional analysis and solving the equation the answer will be 1.40 X 10^25 atoms
 * Here are some more practice problems: How many atoms are in 1.14 mol SO3? How many moles are in 4.65 X 10^24 molecules of NO2?

__ Mass of a Mole of a Compound __
 * Dakota Pimentel (295-296) **
 * To find the mass of a mole, the empirical formula of the compound must first be observed
 * You need to count the amount of molecules for each letter.
 * You need to find the atomic mass of each element and then multiply that number by however many molecules of that element are present in the compound
 * ex: H2O=
 * H --->2 --> 2*1.003
 * O --->1--> 1*16
 * Then add all of the elements in the compound to get the molar mass and add grams
 * 2.006+16=18.006---> [18.006g]
 * "to calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. then add the masses of the elements in the compound"

[]



__** The Mole-Mass Relationship **__** -Elizabeth Howard Page 297 ** > > ** ound to convert between the mass of a substance and the moles of a substance ** [] ** - Video explaining the Mole-Mass Relationship **
 * Elizabeth Howard (297) **
 * ** The molar mass of any substance is the mass in grams of one mole of that substance **
 * ** Use the molar mass of an element or comp **
 * ** Molar Mass=1 Mole **
 * ** Mass (grams) = Number of Moles X Mass (grams) / 1 Mole **
 * ** Example: Find the mass of 3.00 mol of NaCl (which has a molar mass of 58.5g/mol **
 * ** Mass of NaCl = 3.00 mol X 58.5 g / 1 mol = 176 g **




 * Zoey Killion (298) **

__ Converting Moles to Mass __
1. Analyze: //List the knowns and unknowns.// 2. Calculate: //Solve for the unknown.// 3. Evaluate: //Does the result make sense?// **Example:** The aluminum satellite dishes in Figure 1 are resistant to corrosion because the aluminum reacts with oxygen in the air to form a coating of aluminum oxide (Al2O3). This tough, resistant coating prevents any further corrosion. What is the mass of 9.45 mol of aluminum oxide?

1. Analyze: //List the knowns and unknowns.//
Known: number of moles = 9.45 mol Al2O3 Unknown: mass = ? g Al2O3. The mass of the compound is calculated from the known number of moles of the compound. The desired conversion is moles à mass. <span style="color: #000000; font-family: Calibri; line-height: normal; margin: 0in 0in 0pt 0.5in; text-indent: -0.25in;">2. Calculate: //Solve for the unknown.// Determine the molar mass of Al2O3: 1 mol Al2O3 = 102.0g Al2O3 Multiply the given number of moles by the conversion factor relating moles of Al2O3 to grams of Al2O3. Mass = 9.45 mol Al2O3 X (102.0 g Al2O3/ 1 mol Al2O3) = 964g Al2O3 <span style="color: #000000; font-family: Calibri; line-height: normal; margin: 0in 0in 0pt 0.5in; text-indent: -0.25in;">3. Evaluate: //Does the result make sense?// The number of moles of Al2O3 is approximately 10, and each has a mass of approximately 100g. The answer should be about 1000g. The answer has been rounded to the correct number of significant figures. __ Practice Problems: __ Ø Find the mass, in grams of 4.52 X 10-3 mol C20H42. Ø Calculate the mass, in grams, of 2.50 mol of iron (II) hydroxide.

= Caroline Rubino (Co ed = = itor) (299) = = Page 299: Caroline Rubino =

Problem: When iron is exposed to air, it corrodes to form red-brown rust. Rust is iron (III) oxide (Fe2O3). How many moles of iron(III) oxide are contained in 92.2g of pure Fe2O3.
Known Unknown -Mass = 92.2g Fe2O3 - number of moles = ? mol Fe2O3 - the unknown number of moles of the compound is caculated from a known mass of a compound. The conversion is mass moles.
 * 1) ==    ﻿ ﻿ ﻿ ﻿ 1.) Analyze- list the known and unknown==

**2.) Caculate - Solve the Unknown**

 * - Determine the molar mass of Fe2O3 : 1 mol = 159.6G Fe2O3**
 * -Multiply the given mass by the conversion factor relating mass of Fe2O3 to moles of Fe2O3.**
 * Moles = 92.2g Fe2O3 x 1 mol Fe2O3**
 * 159.6g Fe2O3**
 * = .0578 mol Fe2O3**

**3.) Evaluate- Does the result make sense????**

 * - Because the given mass (about 90grams) is slightly larger than the masss of one-half mole of Fe2O3 (about 160g) the answer should be slightly larger than one-half (0.5) mol.**

Mole-Volume Relationship

Shannon Lamy (300)
· The volume of 1 mole of different solids and liquids are different BUT o Why? Because gas molecules are free flowing and there is a lot of space, so the actual size of the gas influences the volume of 1 mole far less than for a liquid or solid Example:

Both are gases with different size molecules, but 1 mole of each has the same volume.

Vs    · 1811 – **Avagadro Hypothesis –** At the same temperature and pressure, equal volume of gases contain equal number of particles, but not necessarily the same size particles · Volume of gas changes at different temperatures and pressures Example: Balloon at room Balloon at cold temperature -volume decreases temperature · Because temperature and pressure impact the volume of gas so much, gases are measured at **Standard Temperature and Pressure (STP)** · **Standard Temperature and Pressure (STP) –** temperature of 0 degrees Celsius and pressure of 101.3 kPa · **Key Fact –** at STP, 1 mole of any gas has a volume of 22.4 o 22.4 = **Molar Volume**

Calculating Volume at STP
Evan Sommerich (301) STP is the relationship that 22.4L = 1 mol.

Volume of gas= Moles pf gas X __22.4 L__ 1 Mole A video that explains how to do the conversions [] Becky Hyatt (302-303)

__ Calculating Molar Mass from Density __ page 302 (Becky Hyatt)  a gas-filled balloon will either sink or float depending on whether the density of the balloon’s gas is greater or less than the density of the surrounding air  molar mass = density at STP x molar volume at STP  grams/mole = grams/L x 22.4 L/1 mole



__ Sample Problem 10.8 __ page 302 (Becky Hyatt) Calculating the Molar Mass of a Gas at STP: The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP. What is the molar mass of the compound?  knowns: density, mol (gas at STP)  unknown: molar mass  use conversion factor 22.4 L/1 mol  molar mass = …  the ratio of the calculated mass to the volume A gaseous compound composed of sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/L at STP. What is the molar mass of this gas?
 * 1) Analyze- List the knowns and the unknown.
 * 1) Calculate- Solve for the unknown.
 * 1) Evaluate- Does the result make sense?
 * Practice Problem:**

__ The Mole Road Map __ page 303 (Becky Hyatt)  the mole is at the center of your chemical calculations  to convert from one unit to another, you must use the mole as an intermediate step  the form of the conversion factor depends on what you know and what you want to calculate



=__ 10.3 Percent Composition and Chemical Formulas __=

Percent Composition

 * The relative amounts of the elements in a compound are expressed as the percent composition or the percent by mass of each element in a compound.
 * The percent composition of a compound consists of a percent value for each different element in the compound.
 * The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100% [[image:http://www.iun.edu/~cpanhd/C101webnotes/quantchem/images/masspercent.jpg width="355" height="67"]]

<span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif;">The Percent Composition of a Compound
An Example of Percent Composition of The Earth's Air
 * <span style="color: #000000; font-family: Arial,Helvetica,sans-serif;">﻿Knowing the relative amounts of the components of a mixture or compound can be very useful
 * <span style="color: #000000; font-family: Arial,Helvetica,sans-serif;">The relative amounts of the elements in a compound are expressed as the percent composition
 * <span style="color: #000000; font-family: Arial,Helvetica,sans-serif;">Percent Composition is the percent by the mass of each element in the compound
 * The Percent composition of a compound consists of a percent value for each different element in the compound
 * As an example, K2CrO4 can be used to show percent composition. The percent composition of it is K=40.3%, Cr=26.8%, and O=32.9%
 * The percents MUST always add up to 100% (For example, in K2CrO4, 40.3% + 26.8% + 32.9% = 100%)
 * Important Concept: The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%

==<span style="font-size: 1.3em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">**<span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif;">Sample Problem: ** == When a 13.60 g sample of a compound containing only magnesium and oxygen is decomposed, 5.40 g of oxygen is obtained. What is the percent composition of this compound?

__** What you know... **__ __** Solving The Problem... **__
 * Mass of compound: 13.60g
 * Mass of Oxygen: 5.40 g O
 * Mass of Magnesium: 13.60g - 5.40g = 8.20g Mg
 * The percent by mass of an element in a compound is the mass of that element divided by the mass of the compound multiplied by 100%.
 * %Mg= (Mass of Mg / Mass of Compound) X 100% = (8.20g / 13.60g) X 100% = **__60.3%__**
 * %O= (Mass of O / Mass of Compound) X 100% = (5.40g / 13.60g) X 100% = **__39.7%__**
 * __ Answers... __**
 * ===**60.3% Magnesium**===
 * ===**39.7% Oxygen**===

Andrea Luongo (307)

 * You can calculate the percent composition of a compound if you know its chemical formula.
 * Subscripts in the formula of the compound are used to calculate the mass of each element in a mole of that compound.
 * The sum of these masses is the molar mass.
 * By using the individual masses of each element and the molar mass you can calculate the percent of each element by molar mass and multiply by 100%.

EX. __Mass of the element compound in 1 mol__ x 100% Molar Mass of Compound
 * Percent Mass: **


 * The percent composition of a compound is always the same.
 * The percents of the elements add up to 100%.
 * Use two significant figures.

**Calculate the Percent Composition** of Propane:
 * EX. **

Mass of C in 1 molC3H8 = 36.0g Mass of H in 1 molC3H8 = 8.0g Molar Mass of C3H8 = 44.0g/mol mass of C3H8 44.0g mass of C3H8 44.0g 81.8 % + 18.0% = about 100%
 * Perecnt C = __mass of C__ x 100%
 * Percent C = __36.0g__ x 100%
 * ** Percent C = 81.8% **
 * Percent H = __mass of H__ x 100%
 * Percent H = __8.0g__ x 100%
 * ** Percent H = 18.0% **


 * TO SEE ANOTHER EXAMPLE OF PERCENT COMPOSITION VISIT: **
 * [] **

Percent Composition as a Conversion Factor
>> **Example Percent Composition Problem**Calculate the percent composition of carbon in each of the following: >> **CO2** >> Molar mass of compound: >> Mass due to carbon: 12.01 g/mol >> Percent composition of carbon: = James Payne (309-310) = = ﻿Empirical Formulas = = ﻿-Gives the lowest whole-number ratio of the atoms of the elements in a coumpound = = -May or may not be the same as a molecular formula = = Example:HO is empirical and H202 is the molecular = = -The molecular formula tells the actual number of each kind of atom present = == =** Mitch Martin (311) **=
 * ==== Percent Composition is used to calculate the number of grams of any element in a specific mass of a compound. ====