The Mole Q: how long would it take to spend a mole of $1 coins if they were being spent at a rate of 1 billion per second?

Measuring the Amount of “Stuff” Suppose you needed to measure the amount of sand in a child’s sandbox… –You could count each grain of sand (the number of particles) –You could weigh the sand (mass) –You could measure how many bucket-fulls of sand there are (volume) –You could use moles to convert the number of particles to mass or to volume and vice versa

1 Mole = 6.02 x particles Defining particles… Elements have particles called Atoms Compounds have particles called Molecules Moles are like measuring cups

Mollionaire Q: how long would it take to spend a mole of $1 coins if they were being spent at a rate of 1 billion per second? A: $ 6.02 x / $ = 6.02 x payments = 6.02 x seconds 6.02 x seconds / 60 = x minutes x minutes / 60 = x hours x hours / 24 = x 10 9 days x 10 9 days / = x 10 7 years A: It would take 19 million years

Comparing sugar (C 12 H 22 O 11 ) & H 2 O No, sugar has more (45:3 ratio) Yes (6.02 x in each) Yes. No, molecules have dif. masses No, molecules have dif. sizes. 1 mol each Yes, that’s what grams are. mass? No, they have dif. molar masses # of moles? No, they have dif. molar masses # of molecules? No # of atoms? No, they have dif. densities. volume? 1 gram eachSame

Example: How many moles of magnesium is 1.25 x atoms of magnesium? 1 mole Mg = 6.02 x atoms Mg Use as a conversion factor in a t-table = 2.08 x mol Mg

Round Table Practice 1.What is Avogadro’s Number? 2.How many moles of sodium is x atoms of sodium? 3.If there are 1.03 x 10 5 mol cesium, then how many atoms are there? 4.If there are x mol of sulfur, then how many atoms are there? 5.How many atoms are in 2.12 mol of propane (C 3 H 8 )? 6.You have 1.14 mol SO 3. a)What is the name of this compound. b) How many atoms are there? 7.a) How many moles are there in 4.65 x molecules of NO 2 b)What is the name of this compound?

Answers to Round Table Practice x particles of a substance x mol Na x atoms Cs x atoms S x atoms in this sample of propane 6.a) sulfur trioxide, b) 2.75 x atoms 7.a) 7.72 mol NO 2 b) nitrogen dioxide

Homework Assignment Section 10.1 wksht, 9-14 pg pg pg. 292 Finish Naming Compounds Review

Molar Mass – Use the Periodic Table The mass of one mole is called “molar mass” Example: 1 mol Li = 6.94 g Li This is expressed as 6.94 g/mol What are the following molar masses? SSO 2 Cu 3 (BO 3 ) g/mol g/mol g/mol Calculate molar masses (to 2 decimal places) CaCl 2 (NH 4 ) 2 CO 3 O 2 Pb 3 (PO 4 ) 2 C 6 H 12 O 6 Cux 3 = x 3= Bx 2 = x 2= Ox 6 = x 6=

Molar mass The mass of one mole is called “molar mass” E.g. 1 mol Li = 6.94 g Li This is expressed as 6.94 g/mol What are the following molar masses? SSO 2 Cu 3 (BO 3 ) g/mol64.06 g/mol g/mol Calculate molar masses (to 2 decimal places) CaCl 2 (NH 4 ) 2 CO 3 O 2 Pb 3 (PO 4 ) 2 C 6 H 12 O g/mol (Ca x 1, Cl x 2) g/mol (N x 2, H x 8, C x 1, O x 3) g/mol (O x 2) g/mol (Pb x 3, P x 2, O x 8) g/mol (C x 6, H x 12, O x 6)

Molar Mass – Don’t be fooled by other names! Gram Atomic Mass (GAM) – molar mass of an element (all atoms are identical) Gram Molecular Mass (GMM) – molar mass of a compound (atoms that are covalently bonded) Gram Formula Mass (GFM) molar mass of an ionic compound (ions bound in specific simple mole ratios)

Converting between grams and moles If we are given the # of grams of a compound we can determine the # of moles, & vise-versa In order to convert from one to the other you must first calculate molar mass Use a t-table to decide which conversion factor to use. 0.25HCl 53.15H 2 SO NaCl 1.27Cu mol (n)gg/molFormula

Homework Assignment 10.2 wksht (mole mass problems – we’ll finish the rest tomorrow) 7,8,15 pg pg , 26, 27 pg. 303

Mole Mass Practice Problems 1.How many moles are represented by 16.0 g of ethanol, C 2 H 5 OH? 2.How many grams of glucose are in 6.63 x molecules of glucose, C 6 H 12 O 6 ? 3.How many moles of methanol, CH 3 OH, are in 6.53 x molecules of methanol? 4.How many moles of sodium chloride are in 16.0 g of sodium chloride? 5.How many molecules, of potassium hydroxide are in 40.6 g? 6.How many grams of chromic chloride are in 7.14 moles of chromic chloride?

Volume of a Mole of Gas Volume varies with a change in temperature of pressure The volume of a gas is usually measured at Standard Temperature and Pressure, STP Standard Temperature: 0 C Standard Pressure: kPa or 1 atm At STP, 1 mole of any gas fills 22.4 L (molar volume of a gas) 22.4 L of a gas at STP has 6.02 x particles

Molar Density Density = Mass. = grams. Volume milliliters Molar Density will always have the same t-table except for the first square

Example Problems Humans take in oxygen to burn glucose and gain energy. The water and carbon dioxide produced in this reaction, called cellular respiration, are exhaled. –If 28 g of water is produced in this reaction, what volume of water vapor could be exhaled? –How many atoms are exhaled if 44.8 L of CO 2 is released? –How many grams of oxygen is consumed in the reaction if the volume of oxygen inhaled was mL?

Homework Assignment Finish 10.2 wksht pg pg , pg. 303

Percent Composition: The relative amounts of each element in a compound expressed as a percent Also called “percent by mass” % means “part over whole” Example: 8.2 g of Magnesium reacts completely with 5.40 g of Oxygen to form a compound. What is the percent composition of each element in the compound?

Solution Mass of MgO = 8.2 g g = g (because the law of conservation of mass is ALWAYS true)

If all you are given is the formula or name of a compound, then you must use Molar Mass from the Periodic Table Example: Calculate the % composition of propane, C 3 H 8. Molar mass of C 3 H 8 = 44.0 g/mol Mass of carbon = 3 x 12 = 36 g/mol Mass of hydrogen = 8 x 1 = 8 g/mol

Percent Composition can also be used as a conversion to solve for mass. Calculate the mass of carbon in 82.0 g of propane C 3 H 8 Molar mass of C 3 H 8 = 44 g/mol Mass of carbon = 3 x 12 = 36 g/mol %C in propane = 81.8%... So if there were 100 g of propane, 81.8g would be C = 67.1 g of C

Empirical and Molecular Formulas Consider NaCl (ionic) vs. H 2 O 2 (covalent) Cl Na Cl Na Chemical formulas are either “simplest” (a.k.a. “empirical”) or “molecular”. Ionic compounds are always expressed as simplest whole number ratios, or formula units. Covalent compounds can either be molecular formulas (H 2 O 2 ) or empirical formulas (HO) H O O H H O O H H O O H

Steps to Calculate the Empirical Formula What is the empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen? 1.Assume that the % given is equal to the number of grams. N = 25.9 gO = 74.1 g 2.Convert the number of grams to moles using GAM.

3.Divide by the lowest number of moles to obtain the simplest whole number ratio 4.If necessary, multiply by a whole number to obtain a whole-number ratio 1 mol N x 2 = 2 mol N 2.5 mol O x = 5 mol O 5. Write the chemical formula using these whole number ratios N2O5N2O5

Q - Write empirical formulas for propene (C 3 H 6 ), ethene (C 2 H 2 ), glucose (C 6 H 12 O 6 ), octane (C 8 H 14 ) Q - Identify these as empirical formula, molecular formula, or both H 2 O, C 4 H 10, CH, NaCl

Answers Q - Write simplest formulas for propene (C 3 H 6 ), C 2 H 2, glucose (C 6 H 12 O 6 ), octane (C 8 H 14 ) Q - Identify these as simplest formula, molecular formula, or both H 2 O, C 4 H 10, CH, NaCl A - CH 2 A - H 2 O is both simplest and molecular C 4 H 10 is molecular (C 2 H 5 would be simplest) CH is simplest (not molecular since CH can’t form a molecule - recall Lewis diagrams) NaCl is simplest (it’s ionic, thus it doesn’t form molecules; it has no molecular formula) CHCH 2 OC4H7C4H7

Determine the Molecular Formula You must know the empirical formula. You must also know the molar mass of the compound. Divide the molar mass of the compound by the empirical formula mass Example: Calculate the molecular formula of a compound whose molar mass is 60.0 g and empirical formula is CH 4 N. CH 4 N = 30 g/mol (using periodic table) ? = 60 g/mol Need twice as much… multiply subscripts in chemical formula by two C 2 H 8 N 2

Homework Assignment 10.3 wksht pg pg pg pg. 312 Pre-Lab Digenite Lab

Digenite Lab – Choose Your Role Alchemist – measures out materials, combines them, and heats them up Mathematician – guides team through the calculations and provides calculator- support Troubadour – tells the story of the lab through careful and detailed observations Scribe – records team data on the class data table and ensures accurate information is recorded by each team member