2.C – Conserving Matter

When a car’s gas empties, where do the atoms in the gasoline go?

Do Now How many and what type of atoms are in the following examples: A. CH4 B. 4NH3 C. 6Ca(OH)2 D. Al2(NO3)3

C.5 The Mole Concept Definition: Mole – SI unit for counting 1 Mole of Particles: Contains 6.02 x 1023 particles Adopted from "Chemistry You Need to Know" by Kelly Deters

What is a counting unit? You’re already familiar with one counting unit…a “dozen” A dozen = 12 “Dozen” 12 A dozen doughnuts 12 doughnuts A dozen books 12 books A dozen cars 12 cars A dozen people 12 people Adopted from "Chemistry You Need to Know" by Kelly Deters

How big is a mole? Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole. Adopted from "Chemistry You Need to Know" by Kelly Deters

A Mole of Particles Contains 6.02 x 1023 particles 1 mole C = 6.02 x 1023 C atoms 1 mole H2O = 6.02 x 1023 H2O molecules 1 mole NaCl= 6.02 x 1023 NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions Adopted from "Chemistry You Need to Know" by Kelly Deters

What does a “mole” count in? A mole = 6.02  1023 (called Avogadro’s number) 6.02  1023 = 602,000,000,000,000,000,000,000 “mole” 6.02  1023 1 mole of doughnuts 6.02  1023 doughnuts 1 mole of atoms 6.02  1023 atoms 1 mole of molecules 6.02  1023 molecules This means a 12 ounce bottle of water would have 19.7 “moles” of water…a much easier-to-work-with number! Adopted from "Chemistry You Need to Know" by Kelly Deters

Molar Mass What is molar mass? Adopted from "Chemistry You Need to Know" by Kelly Deters

Definition Molar Mass – The mass for one mole of an atom or molecule. Other terms commonly used for the same meaning: Molecular Weight Molecular Mass Formula Weight Formula Mass Adopted from "Chemistry You Need to Know" by Kelly Deters

Mass for 1 mole of atoms The average atomic mass = grams for 1 mole Average atomic mass is found on the periodic table Element Mass 1 mole of carbon atoms 12.01 g 1 mole of oxygen atoms 16.00 g 1 mole of hydrogen atoms 1.01 g Unit for molar mass: g/mole or g/mol Adopted from "Chemistry You Need to Know" by Kelly Deters

Molar mass for molecules The molar mass for a molecule = the sum of the molar masses of all the atoms Adopted from "Chemistry You Need to Know" by Kelly Deters

Calculating a Molecule’s Mass To find the molar mass of a molecule: 1 Count the number of each type of atom 2 Find the molar mass of each atom on the periodic table 3 Multiple the # of atoms  molar mass for each atom 4 Find the sum of all the masses Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for CaBr2 Example: Molar Mass Example: Find the molar mass for CaBr2 Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for CaBr2 Example: Molar Mass 1 Count the number of each type of atom Example: Find the molar mass for CaBr2 Ca 1 Br 2 Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for CaBr2 Example: Molar Mass 2 Find the molar mass of each atom on the periodic table Example: Find the molar mass for CaBr2 Ca 1 40.08 g/mole Br 2 79.91 g/mole Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for CaBr2 Example: Molar Mass 3 Multiple the # of atoms  molar mass for each atom Example: Find the molar mass for CaBr2 Ca 1  40.08 g/mole = 40.08 g/mole Br 2  79.91 g/mole = 159.82 g/mole Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for CaBr2 Example: Molar Mass 4 Find the sum of all the masses Example: Find the molar mass for CaBr2 Ca 1  40.08 g/mole = 40.08 g/mole Br 2  79.91 g/mole = + 159.82 g/mole 199.90 g/mole 1 mole of CaBr2 molecules would have a mass of 199.90 g Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass & Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Sr(NO3)2 Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Molar Mass & Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Sr(NO3)2 Sr 1  87.62 g/mole = 87.62 g/mole N 2  14.01 g/mole = 28.02 g/mole O 6  16.00 g/mole = + 96.00 g/mole 211.64 g/mole 1 mole of Sr(NO3)2 molecules would have a mass of 211.64 g Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for Al(OH)3 Let’s Practice #2 Example: Find the molar mass for Al(OH)3 Adopted from "Chemistry You Need to Know" by Kelly Deters

Find the molar mass for Al(OH)3 Let’s Practice #2 Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Al(OH)3 Al 1  26.98 g/mole = 26.98 g/mole O 2  16.00 g/mole = 32.00 g/mole H 2  1.01 g/mole = + 2.02 g/mole 61.00 g/mole 1 mole of Al(OH)3 molecules would have a mass of 61.00 g Adopted from "Chemistry You Need to Know" by Kelly Deters

Using Molar Mass in Conversions What is molar mass? Adopted from "Chemistry You Need to Know" by Kelly Deters

Do Now: Take out your homework. Find the molar mass of H2O

Example: Moles to Grams How many grams are in 1.25 moles of water? Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Moles to Grams When converting between grams and moles, the molar mass is needed Example: How many grams are in 1.25 moles of water? H O 2 1 1.01 g/mole 16.00 g/mole  = 2.02 g/mole + 18.02 g/mole 1 mole H2O molecules = 18.02 g 1.25 mol H2O 18.02 g H2O = _______ g H2O 22.53 1 mol H2O Adopted from "Chemistry You Need to Know" by Kelly Deters

How many moles are in 25.5 g NaCl? Let’s Practice #3 Example: How many moles are in 25.5 g NaCl? Adopted from "Chemistry You Need to Know" by Kelly Deters

How many moles are in 25.5 g NaCl? Let’s Practice #3 Example: How many moles are in 25.5 g NaCl? Na Cl 1 22.99 g/mole 35.45 g/mole  = + 58.44 g/mole 1 mole NaCl molecules = 58.44 g 25.5 g NaCl 1 mole NaCl = _______ mole NaCl 0.44 58.44 g NaCl Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Grams to Molecules How many molecules are in 25.5 g NaCl? Adopted from "Chemistry You Need to Know" by Kelly Deters

Example: Grams to Molecules How many molecules are in 25.5 g NaCl? Na Cl 1 22.99 g/mole 35.45 g/mole  = + 58.44 g/mole 1 moles NaCl molecules = 58.44 g 1 mol = 6.021023 molecules 25.5 g NaCl 1 mol NaCl 6.021023 molecules NaCl 58.44 g NaCl 1 mol NaCl = _________ molecules NaCl 2.63  1023 Adopted from "Chemistry You Need to Know" by Kelly Deters

Practice: Solve the following problem: How many moles are in 6.7 g of NaCl? Given: Attain:

Objectives SWBAT practice conversions between moles and grams SWBAT practice conversions between moles and molecules

How many moles are in a sample of 2.75 × 1024 molecules of SrCl2? Let’s Practice #4 Example: How many moles are in a sample of 2.75 × 1024 molecules of SrCl2? Adopted from "Chemistry You Need to Know" by Kelly Deters

How many moles are in a sample of 2.75 × 1024 molecules of SrCl2? Let’s Practice #4 Example: How many moles are in a sample of 2.75 × 1024 molecules of SrCl2? 1 mol = 6.021023 molecules 2.75 × 1024 molecules SrCl2 1 mol SrCl2 6.02 × 1023 molecules SrCl2 = __4.56__ mol SrCl2 Adopted from "Chemistry You Need to Know" by Kelly Deters

REMEMBER: If you are going between moles and mass use MOLAR MASS. 1 mole molar mass (g) molar mass (g) 1 mole If you are going between moles and molecules (atoms) use AVOGADROS NUMBER. 6.02 X 1023 molecules 1 mole . 1 mole 6.02 X 1023 molecules

Practice: Solve the following problem: How many molecules are in 0.8 moles of NaCl? A. Given: Unknown (attain): B. What is your conversion factor? C. Solve:

GRAMS to MOLECULES How many molecules are in 4.6 grams of HCl?

Objective 1. SWBAT review problems where molar mass converts between moles and grams. 2. SWBAT determine molar relationships amount reactants and products in a chemical equation.

Practice: Solve the following problem: How many moles are in 2.8 g of HCl? A. Given: Unknown (attain): B. What is your conversion factor? C. Solve:

DO NOW 1. How many moles are in 2.3 X 1024 molecules of NaCl? 2. How many moles are in 6.8 X 1026 molecules of CO2? 3. How many molecules are in 2.3 moles of HCl? Adopted from "Chemistry You Need to Know" by Kelly Deters

Objectives 1. SWBAT define the law of conservation of mass. 2. SWBAT review reactants, products, coeiffients, and determining the number of atoms in a given formula. 3. SWBAT balance chemical equations with a partner.

Keeping Track of Atoms Law of Conservation of Matter: Matter is neither created nor destroyed. Since chemical reactions cannot create or destroy atoms, chemical equations representing the reactions must always be BALANCED.

Atomic Perspective: C O2  CO2 1 Carbon atom 1 oxygen molecule  1 carbon dioxide molecule What are the reactants in this chemical equation? What are the products in this chemical equation? Are there the same number of atoms on both sides of the equation? Where any atoms destroyed or created? Was the Law of Conservation of Matter maintained?

2 Cu (s) + O2 (g)  2 CuO (s) COEFFICIENTS - indicates the number of units of each substance involved. Does the oxygen molecule have a coefficient? What do the subscripts represent? Can subscripts be removed from chemical equations?

DO NOW 2 Cu (s) + O2 (g)  2 CuO (s) What are the reactant(s) in this chemical equation? What are the product(s) in this chemical equation? Are there the same number of atoms on both sides of the equation? Where any atoms destroyed or created? Was the Law of Conservation of Matter maintained?

How do we Balance Equations? Number of compounds in the reaction Coefficients 2 H2 + O2  2 H2O Subscripts # of atoms in a compound Subscripts balance charges within a compound. Coefficients balance atoms in an equation

What do Coefficients Really Mean? CH4 + 2 O2  CO2 + 2 H2O Total: 1 C 4 H 4 O Total: 1 C 4 H 4 O The equation is balanced.

Make an atom inventory for the following equation Al2O3 + HCl -> AlCl3 + H2O Is it Balanced?

SWBAT Practice balancing equations in groups.

How to Balance By Inspection: 1 Make a table of elements _____ C H4 + _____ O2  _____ H2 O + _____ C O2 Reactants Products C H O Taken from Kelly Deters

How to Balance By Inspection: 2 Count the number of each element or ion on the reactants and products side. Don’t forget to add all the atoms of the same element together—even if it appears in more than one compound! _____ C H4 + _____ O2  _____ H2 O + _____ C O2 Reactants Products C 1 1 H 4 2 O 2 3 Taken from Kelly Deters

How to Balance By Inspection: 3 Add coefficients to balance the numbers Each time you add a coefficient, update your table with the new quantities of each atom. _____ C H4 + _____ 2 O2  _____ 2 H2 O + _____ C O2 Reactants Products C 1 1 H 4 2 4 O 2 4 3 4 Taken from Kelly Deters

How to Balance By Inspection: 4 Place a “1” in any empty coefficient location Filling each coefficient location lets you and the grader know that you finished the problem rather than you left some blank because you weren’t done! _____ 1 C H4 + _____ 2 O2  _____ 2 H2 O + _____ 1 C O2 Reactants Products C 1 1 H 4 2 4 O 2 4 3 4 Taken from Kelly Deters

Choosing the Order of Balancing How do you know what order to balance in? Start Elements that appear only 1 time per side Save for later Elements that are uncombined Pb + PbO2 + H+  Pb2+ + H2O Start Elements in most complicated molecules Save for later Elements that appear more than 1 time per side To balance this equation, use the order: O, H, Pb Taken from Kelly Deters

How is Balancing Affected by Order? What happens if we balance in the order determined in the last slide? O, H, Pb _____ 1 Pb + _____ 1 Pb O2 + _____ 4 H+  _____ 2 H2 O + _____ 2 Pb2+ Reactants Products O 2 1 2 H 1 4 2 4 Pb 2 1 2 Taken from Kelly Deters

What about a different order? How is it different if we balance in a different order? H, O, Pb 4 _____ 1 Pb + _____ 1 Pb O2 + _____ 2 H+  _____ 2 H2 O + _____ 2 Pb2+ Reactants Products  H 1 2 4 2 4 O 2 1 2 Pb 2 1 2 You’ll still get to the correct answer, but it will take longer and be more complicated! Taken from Kelly Deters

Balance the following equation Let’s Practice #1 Example: Balance the following equation __ HCl + __ Ca(OH)2  __ CaCl2 + __ H2O Taken from Kelly Deters

Balance the following equation Let’s Practice #1 Example: Balance the following equation Did you see the “OH” polyatomic ion & change H2O to HOH? 2 1 1 2 __ HCl + __ Ca(OH)2  __ CaCl2 + __ H2O HOH Taken from Kelly Deters

Balance the following equation Let’s Practice #2 Example: Balance the following equation __ H2 + __ O2  __ H2O Taken from Kelly Deters

Balance the following equation Let’s Practice #2 Example: Balance the following equation 2 1 2 __ H2 + __ O2  __ H2O Taken from Kelly Deters

Balance the following equation Let’s Practice #3 Example: Balance the following equation __ Fe + __ O2  ___ Fe2O3 Taken from Kelly Deters

Balance the following equation Let’s Practice #3 Example: Balance the following equation 4 3 2 __ Fe + __ O2  ___ Fe2O3 Taken from Kelly Deters

Do Now Balance the following equations: __Cu +__AgNO3 -> __Cu(NO3)2 + __Ag ___NaClO3 --> ___NaCl + ___O2

Objectives 1. SWBAT define mole, representative particle, and molar mass. 2. SWBAT calculate the molar mass of substances.

Do Now Take out your homework. Take out a calculator. ___H2O2 _____H2O + _____O2

Objectives SWBAT determine the molar mass of different atoms or formulas. SWBAT convert between grams and moles.

Objectives SWBAT practice conversions between moles and grams SWBAT practice conversions between moles and molecules

Steps to Solving Equations and Molar Relationships 1. Balance the equation. 2. State the GIVEN and what you want to ATTAIN (UNKOWN) 3. Figure out conversions. 4. SOLVE!

WORKSHEET PROBLEM #1 MOLES TO MOLES ___Mg + ____O2 -> ____MgO How many moles of Mg are needed to produce 6 moles of MgO? How many moles of O2 are needed to produce 4 moles of MgO? How many moles of MgO will be produced when 7 moles O2 enter the reaction?

PROBLEM #1 MOLES TO MOLES to Grams 2H2O2 -> 2H2O + O2 How many grams of H2O2 are needed to produce 6 moles of O2?

DO NOw For the following equation: ____Cu + ____O2 -> ____CuO 1. How many moles of Cu are needed to react with 15 moles O2? 2. How many moles of CuO produced when 11 moles Cu react with sufficient O2?

Objectives SWBAT calculate moles of product and moles of reactants. SWAT answer questions on molar mass, g to molecules, and stoichometry.

DO NOW: ___C5H12 + ___O2 --> ___CO2 + ___H2O If 10 moles of C5H12 enter the reaction, how many moles of H2O are produced? If 13 moles CO2 are produced, how many moles O2 went in? If 10 moles of C5H12 enter the reaction, how many grams of H2O are produced?

Do Now 2Cu + O2 -> 2CuO How many moles of Cu are needed to react with 5.6 moles O2 ? How many grams of Cu will be needed to react with 5.6 moles O2 ?

Objectives 1. SWBAT calculate percent compositions. 2. SWBAT explain why knowledge of percent compositions is important to the mining process.

Percent Composition Percent by mass of each material found in a formula unit. Ex. In Cu2S, it is 80% copper.

Determining Percent Composition 1. Find the molar mass of the formula unit. 2. Find the percentage by dividing the part by the whole and multiplying by 100.

Example

Let’s Try this one Find the percent oxygen in the following formulas: CO2 C6H12O6

Think-Pair-Share

How is percent composition important when mining metals? How is it important when selecting your metal for your coin?

Do Now What percent of oxygen is found in Calcium Nitrate? Ca(NO3)2