# Chapter 2: Matter and Change - Mrs. Williams Chemistry

Chapter 10 Chemical Quantities Yes, you will need a calculator for this chapter! Mole Activity #1 How do we measure items? You can measure mass, volume,

or you can count pieces. grams. We measure volume in liters. We count pieces in MOLES. We measure mass in The Mole Song http://www.youtube.com/watch?v=PvT51M

0ek5c Yes, you must sing along with the chorus! Moles (is abbreviated: mol) Avogadros number. 1 mole = 6.02 x 1023 of the representative particles.

Representative Particles The smallest pieces of a substance Most elements = atoms BrINClHOF = molecules because they always come in twos

Br2 I2 O2 etc Covalent compounds = molecules H2O, SO2 Ionic compounds = formula units or ions NaCl = 1 formula unit or NaCl = 2 ions Na+ and Cl Something with a charge= Ion Representative Particles

CO2 Fe CaO Li+1 Nitrogen gas Sulfur 8 Conversion Factors

2 possible conversion factors for the mole OR 1 mole 6.02 x 1023 representative particles 6.02 x 1023 representative particles 1 mole

Conversion Factors Using the conversion factors we can determine the number of atoms that are in a mole of a compound or how many moles are in a sample of a compound How many molecules are in 2.12 mole of carbon dioxide?

2.12 mole CO2 1 6.02 x 10 23 molecules of CO2 1 mole CO2 = _________ 1.28 x 1024 molecules of CO2

Practice Problem #1 Magnesium is a light metal that is used in the manufacture of aircrafts, automobile wheels, and tools. How many moles of magnesium is 1.25 x 1023 atoms of magnesium? 1.25 x 1023 atoms Mg 1 mole of Mg

1 6.02 x 1023 atoms Mg 0.208 moles =__________ of Mg Try This

How many moles are in 2.4 x 1023 formula units LiO How many formula units are in 1.2 mol LiO V. Chemical Measurements Atomic Mass measured in amu Atomic mass units Bottom number on the periodic table

Find the atomic mass of each atom Mass of O 15.999 amu Mass of Fe 55.847 amu Mass of C 12.011 amu

Mass of a Compound FORMULA MASS sum of the atomic masses in a compound What is the mass of one molecule of water? H2O 2 hydrogen atoms and 1 oxygen 2 (1.01 amu) + 1 (16.00 amu) = 18.02 amu Find the mass of C2H3O2 C: 2 atoms x 12 amu =

24.02 amu H: 3 atoms x 1 amu = 3.03 amu 0: 2 atoms x 16 amu = 32.00 amu Total = 59.05 amu Find the mass of Sr(NO3)2

Molar Mass Mass of 1 mole of something = its MOLAR MASS Molar mass = atomic/formula mass in grams Practice Problems 1 mol Fe = ______ g Fe 1 mol O = ______ g O

1 mol CaCO = ______ g CaCO Practice Problems 1 mol Fe = _55.8_ g Fe 1 mol O = _32.0_ g O 1 mol CaCO = _100.01_ g CaCO 10.2 18

Conversion Factors Involving Molar Mass There are two possible conversion factors relating molar mass and number of moles 1 mole molar mass

molar mass 1 mole OR What is the mass of 3.25 mole of potassium? Follow the steps for conversion problems 3.25 mole K 39.098 g of K 1

1 mole K 127.1 = ___________ g of K Practice Problem #1 How many moles is 5.69 g of NaOH? 5.69 g NaOH

1 1 mole NaOH 39.997 g NaOH 0.142 mole NaOH Practice Problem #2 When iron is exposed to air it corrodes to form red-brown rust. Rust is iron(III) oxide. How

many moles of iron(III) oxide are contained in 92.2 grams of iron(III) oxide? 92.2 g Fe2O3 1 mole Fe2O3 159.691 g Fe2O3 = 0.577moles of Fe2O3

VII. Standard Temperature and Pressure (STP) Practice Problem #1 How many moles is 5.67 L of O2 at STP? 5.67 L O2 1 1 mole O2

22.4 L O2 = 0. 253 moles of O2 Practice Problem #2 What is the volume of 8.8 g of CH4 gas at STP? 8.8 g CH4

1 mole CH4 1 16.063 g CH4 12.27 L CH 22.4 L CH4 = _______ 4 1 mole CH4

Summary of Conversion Factors These four items are all equal: a) 1 mole b) molar mass (in grams/mole) c) 6.022 x 1023 representative particles d) 22.4 L of gas at STP

The Mole Road Map for Conversion Factors Chapter 10 Section 3 Chemistry Essential Questions How do you calculate percent composition? What is an empirical formula? How can you tell the difference between an

empirical formula and molecular formulas? Percent Composition Percent composition is the percent by mass of an element within a compound. There are two ways of finding percent composition:

Percent Composition (cont) Propane (C3H8) is a fuel used commonly in gas grills, find the percent composition of propane. 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?

Percent Composition (cont) Find the percent comp for a 2.50 g sample containing 0.0625g Cu and 2.44 g Zn. Find the percent comp of CO2 Find percent comp (NH4)2CO3 Find percent comp of NH3 Find percent comp of Fe2(SO4)3

Formulas The empirical formula of a compound shows the smallest whole-number ratio of the atoms in the compound. The molecular formula of a compound is either the same as its empirical formula, or it is a simple whole-number multiple of its empirical formula.

Formulas (cont) Identify if the following formulas are empirical, molecular or both. N2O4

H2N CH C3H6 Essential Questions How do you calculate percent composition? What is an empirical formula? How can you tell the difference between an empirical formula and molecular formulas?

Chapter 10 Section 3 P 312 #41-44, 46 P 315-317 #63, 67

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