WELCOME BACK FROM SPRING BREAK

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Angelina Jennings
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1 7 MOLES & CHEMICAL COMPOSITION WELCOME BACK FROM SPRING BREAK BELL RINGER (1) WHAT WAS THE MOST IMPORTANT CHEMICAL STORY THAT YOU HEARD ABOUT OVER BREAK? Short paragraph name, date, period Part 2 Brainstorm a list of what you know about percentages. (same page) WHAT WE NEED TO KNOW RECAP WATCH AND LISTEN LET YOU KNOW WHEN TO WRITE --!!!LISTEN!!! Molar Conversions Section 3 Formulas and Percentage Composition Avogadro s Number and the Mole The SI unit for amount is called the mole (mol). A mole is the number of atoms in exactly 12 grams of carbon-12. The number of particles in a mole is called Avogadro s Number. Avogadro s number is units/mole. Avogadro s Number and the Mole, continued The Mole Is a Counting Unit The mole is used to count out a given number of particles, whether they are atoms, molecules, formula units, ions, or electrons. 1 mole = particles

The Mole Avogadro s Number and the Mole, CONVERSION FACTOR Counting units are used to make conversion factors. one mole is 6.

Conversion Factors Cancel the Given Units Converting Between Amount in Moles and Number of Particles All conversion factors are equal to 1, so you

2 The Mole Avogadro s Number and the Mole, CONVERSION FACTOR Counting units are used to make conversion factors. one mole is particles = 1 mol The conversion factor is particles 1mol = 1 Avogadro s Number and the Mole, cont. Conversion Factors Cancel the Given Units Converting Between Amount in Moles and Number of Particles All conversion factors are equal to 1, so you can use them to convert among different units. You know which conversion factor to use: the needed conversion factor should cancel the units of the given quantity to give you the units of the answer.

3 Converting Amount in Moles to Number of Particles Sample Problem A Solution, continued 2.5 mol SO 2? =? molecules SO molecules SO 2 2.5mol SO 1mol SO =? moleculesso mol SO 2 = molecules SO 2 Avogadro s Number and the Mole, continued CONVERT Number of Particles to Amount in Moles Here is the The reverse calculation where the conversion factor is inverted to get the correct units in the answer. example: How many moles are iron(iii) ions? 3+ 1molFe ions Fe = mol Fe ions Fe Converting Number of Particles to Amount in Moles Sample Problem B Solution, molecules SO 2? =? mol SO 2 1molSO molecules SO =? mol SO molecules SO molecules SO 2 = mol SO 2 Molar Mass Relates Moles to Grams Amount in Moles Can Be Converted to Mass The molar mass is the mass in grams of one mole of an element or compound. Molar mass = the atomic mass of monatomic elements & the formula mass of compounds or diatomic elements. The units for molar mass are g/mol. Use Molar mass as a conversion factor to convert between mass and amount.

Molar Mass Molar Mass as a Conversion Factor Molar Mass Relates

particles to mass, use a twopart process: 1) convert # of

2) convert amount in moles to mass in grams.

4 Molar Mass Molar Mass as a Conversion Factor Molar Mass Relates Moles to Grams, in Chemical Conversions To convert number of particles to mass, use a twopart process: 1) convert # of particles to amount in moles. 2) convert amount in moles to mass in grams. Converting Between Mass, Amount, and Number of Particles One step common to many problems in chemistry is converting to amount in moles.

Converting Number of Particles to Mass Sample Problem C Solution, continued 24 1 mol 12.01 g C 2.44 10 atoms 6.022 10 atoms 1 mol = 48.

5 Converting Number of Particles to Mass Sample Problem C Solution, continued 24 1 mol g C atoms atoms 1 mol = 48.7 g C Mass Can Be Converted to Amount in Moles Convert from mass to # of particles is the reverse operation from the previous problem. To convert from mass to number of particles, you must use a two-part process: 1) convert mass in grams to amount in moles. 2) convert amount in moles to # of particles. Converting Mass to Number of Particles Sample Problem D Solution, continued 1 mol molecules 47.5 g C3H8O g C 3 H 8 O 3 1 mol = molecules Molar Mass Relates Moles to Grams, continued Remember to Round Consistently answer must never be given to more significant figures than is appropriate. Round molar masses from the periodic table to two significant figures to the right of the decimal point.

Objectives Use a periodic table or isotopic composition data to determine the average atomic masses of elements. Infer information about a compound from its chemical formula.

6 Objectives Use a periodic table or isotopic composition data to determine the average atomic masses of elements. Infer information about a compound from its chemical formula. Determine the molar mass of a compound from its formula. Average Atomic Mass and the Periodic Table Most Elements are a Mixture of Isotopes Isotopes - atoms that have different numbers of neutrons than other atoms of the same element do. Average atomic mass is a weighted average of the atomic mass of an element s isotopes. If you know the abundance of each isotope, you can calculate the average atomic mass of an element. Average Atomic Mass Calculating Average Atomic Mass Sample Problem E The mass of a Cu-63 atom is amu, & that of a Cu-65 atom is amu. Use the data below to find the average atomic mass of copper. abundance of Cu-63 = 69.17% abundance of Cu-65 = 30.83%

$Calculating Average Atomic Mass The contribution of each isotope is equal to its atomic mass multiplied by the fraction of that isotope. contribution of Cu-63: 62.94 amu 0.$

7 Calculating Average Atomic Mass The contribution of each isotope is equal to its atomic mass multiplied by the fraction of that isotope. contribution of Cu-63: amu contribution of Cu-65: amu Average atomic mass is the sum of the individual contributions: (62.94 amu ) + (64.93 amu ) = amu Express Composition A compound s chemical formula tells you which elements, & how much of each, are present in a compound. Formulas for covalent compounds show the elements and the number of atoms of each element in a molecule. Formulas for ionic compounds show the simplest ratio of cations and anions in any pure sample. and Moles, continued Formulas Express Composition, continued Any sample of compound has many atoms and ions, and the formula gives a ratio of those atoms or ions. and Moles, continued Formulas Give Ratios of Polyatomic Ions Formulas for polyatomic ions show the simplest ratio of cations and anions. They also show the elements and the number of atoms of each element in each ion. For example, the formula KNO 3 indicates a ratio of one K + cation to one NO 3 anion.

6 atomic # C symbol Carbon name of element atomic mass. o Examples: # 1 mol C = g # 1 mol O = g # 1 mol H = 1.

6 atomic # C symbol Carbon name of element atomic mass. o Examples: # 1 mol C = g # 1 mol O = g # 1 mol H = 1. 7.1 AVOGADRO S NUMBER AND MOLAR CONVERSIONS CHEMISTRY NOTES Identify the mole as the unit used to count particles, whether atoms, ions, or molecules. Use Avogadro s number to convert between amount in