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THE MOLE

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What is the Mole? 6.02 x OR

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What is a dozen? 1 dozen = 12

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Why dont we just say 12? …and it doesnt matter what the objects are… a dozen means 12 whether it is a dozen eggs, a dozen roses, or a dozen ugly hats It is often easier to group objects when counting them 2 dozen = 24 3 dozen = 36

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A mole is a counting unit. It tells us how many objects there are. A pair and a dozen are also counting units. Pair means2 objects Dozenmeans12 objects Molemeans 6.02x10 23 objects So what is a mole?

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It is just a term used to represent a number 2 = pair 12 = 1 dozen 6.02 x = 1 mole 2 = pair 12 = 1 dozen 6.02 x = 1 mole …and we call 6.02 x Avagadros number

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Avogadros number = 6.02 x = Avogadro - He didnt actually identify the number – but it was named after him to honor his many contributions to chemistry – but it was named after him to honor his many contributions to chemistry

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What counting unit would you use for these objects? So why is it such a big number? PAIR

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What counting unit would you use for these objects? So why is it such a big number? DOZEN

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What counting unit would you use for these objects? So why is it such a big number? Since atoms and molecules are very small, the quantity used to measure them needs to be a very large number MOLE

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So why is it such a big number? Since a mole is such a large number, it is useful only for counting very small objects like atoms and molecules. A mole of donuts is too many to eat. Like a pair (2) or a dozen (12), the quantity of a mole (6.02 x ) never changes, but unlike a pair or a dozen, its value is very, very large

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6.02 x particles 6.02 x particles 1 mole 1 mole or or 1 mole 1 mole 6.02 x particles Note that a particle could be an atom OR a molecule! Avogadros Number as Conversion Factor

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1. Number of atoms in mole of Al Practice a) 500 Al atoms b) 6.02 x Al atoms c) 3.01 x Al atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x mole S atoms 2. Number of moles of S in 1.8 x S atoms mole Al | 6.02*10 23 atoms = |1 mole a) 500 Al atoms b) 6.02 x Al atoms c) 3.01 x Al atoms 1.8 *10 24 atoms S | 1 mole = | 6.02*10 23 atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x mole S atoms

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REPRESENTATIVE PARTICLES & MOLES ATOMIC NITROGEN ATOMN 6.02x10 23 NITROGEN GAS MOLEC. N2N2N2N2 6.02x10 23 WATERMOLEC. H20H20H20H20 CALCIUM ION ION Ca x10 23 CALCIUM FLUORIDE FORMULA UNIT CaF x10 23

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What if I asked you how many atoms are in a mole of a compound? –you must know how many atoms are in a representative particle or cluster of the compound. To do this you must know the chem formula –For example, each molecule of CO 2 is composed of 1 C + 2 Os = 3 atoms 1 mole of carbon dioxide molecules contains avogadros number of carbon dioxide molecules. –Thus a mole of CO 2 contains three times avogadros number of atoms What if I asked you how many atoms are in a mole of a compound? –you must know how many atoms are in a representative particle or cluster of the compound. To do this you must know the chem formula –For example, each molecule of CO 2 is composed of 1 C + 2 Os = 3 atoms 1 mole of carbon dioxide molecules contains avogadros number of carbon dioxide molecules. –Thus a mole of CO 2 contains three times avogadros number of atoms

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To find the # of atoms in a mol of a compound, –You 1 st determine the # of atoms in a representative particle of that compound –And then multiply that # of atoms by avogadros # To find the # of atoms in a mol of a compound, –You 1 st determine the # of atoms in a representative particle of that compound –And then multiply that # of atoms by avogadros # How many atoms of carbon are in 2.12 mols of propane molecules (C 3 H 8 )? Useful Info: 1 mol C 3 H 8 = 6.02x10 23 molecules C 3 H 8 1molecule C 3 H 8 = 3 atoms of C Useful Info: 1 mol C 3 H 8 = 6.02x10 23 molecules C 3 H 8 1molecule C 3 H 8 = 3 atoms of C

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1 st we need to see how many molecules of propane we have if we have 2.12 moles. 6.02x10 23 molec C 3 H 8 1 mole C 3 H moles C 3 H 8 X molec C 3 H 8 = = X = 1.276x10 24 molecules of C 3 H 8 (1molecC 3 H 8 )(X)=(1.276x10 24 molecmolsC 3 H 8 ) (1 molec C 3 H 8 )

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2 nd we need to see how many atoms of C if we have 1.276x10 24 molecs of C 3 H 8. 3 atoms of C 1 molecule C 3 H x10 24 molec C 3 H 8 X atoms C = = X = 3.83x10 24 atoms of Carbon (1 molec C 3 H 8 )(X)=(3.83x10 24 molec atoms C) (1 molec C 3 H 8 )

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So the mole can be used to measure any kind of particle – atoms, ions, molecules, formula units It is possible to have a mole of iron atoms, a mole of water molecules and a mole of sodium chloride – all contain 6.02 x particles But do 1 mol of iron, 1 mol of water and 1 mol of sodium chloride all have the same mass? NO!!

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Do a dozen donuts, a dozen books and a dozen bricks weigh the same? NO, so neither do a mole of different atoms, ions or molecules

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Each sample contains 1 mol (6.02 x atoms) 12.0g carbon 32.0g sulfur65.38g zinc Which element do you think has the heaviest atoms?

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So now that we know what a mole of atoms looks like…where did the number come from?

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CARBON!! Scientists took 12g of pure carbon-12 (composed of 6 protons + 6 neutrons; mass number = 12) (composed of 6 protons + 6 neutrons; mass number = 12) and counted how many carbon atoms and counted how many carbon atoms were in the sample Guess how many there were? 6.02 x atoms Why use 12 grams? They wanted the mass of one mole to be the same as the mass number

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6.02 x10 23 atoms of Carbon This pile of carbon-12 weighs 12.0 grams and contains 6.02 x carbon atoms This is one mole of carbon

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This pile of sulfur contains 6.02x10 23 atoms of sulfur. This is one mole of sulfur. Review: A mole is a simple way of saying we have 6.02x10 23 objects. have 6.02x10 23 objects.

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Atomic molar mass of an element = is the average mass (g) of one mole of atoms of that element

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Back to carbon…. Here is one mole of carbon which weighs 12.0 g The atomic molar mass of carbon on the periodic table is…. Which means there are g for every mol of carbon g/mol atomic molar mass of an element = mass (g) of one mole of atoms of that element

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Here is grams of the element zinc. How many moles of zinc do we have? 1 mole. atomic molar mass of an element = mass (g) of one mole of atoms of that element

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This pile of sulfur contains 6.02x10 23 atoms of sulfur (or 1 mole of sulfur) What is the mass, in grams, of this sample of sulfur? atomic molar mass of an element = mass (g) of one mole of atoms of that element g

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0.50 moles x (63.55 g/mole) = 31.8g Here is 0.50 moles of copper. How many grams of copper do we have? 31.8g 0.50 moles | g= 31.8g | 1 mole)

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This pile of powdered iron contains 3.01x10 23 atoms. What is its mass? 27.9 g 3.01x10 23 atoms| 1 mole =.50 moles | 6.02 *10 23 atoms 0.50 moles | g Fe = 27.9 g Fe | 1 mole 3.01x10 23 atoms| 1 mole Fe | g = 27.9g Fe | 6.02 *10 23 atoms Fe | 3.01x10 23 atoms| 1 mole Fe | g = 27.9g Fe | 6.02 *10 23 atoms Fe | 1mole Fe

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Molar mass = the mass of one mole of a substance So now were not talking about individual elements but molecules and compounds I.e. What is the molar mass of water? The formula for water is: H 2 O, so one molecule contains 2 hydrogen atoms and 1 oxygen atom

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Atomic molar mass of H = 1.01g/mol x 2 = 2.02 g/mol Atomic molar mass of O = 16.00g/mol x 1 = 16.00g/mol Molar mass of water H 2 O is 18.02g/mol Molar mass = the mass of one mole of a substance

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Other Names Related to Molar Mass Molecular Mass/Molecular Weight: If you have a single molecule, mass is measured in amus instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different. (This is the beauty of Avogadros Number!) Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different. THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units

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Molar mass Now you try it… What is the molar mass of methane CH 4(g) ? C = g/mol x 1 = g/mol H = 1.01g/mol x 4 = 4.04 g/mol Molar mass of methane = g/mol

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Now you try it… What is the molar mass of methanol CH 3 OH? C = g/mol x 1 = g/mol H = 1.01g/mol x 4 = 4.04 g/mol O = 16.00g/mol x 1 = g/mol Molar mass of methanol = g/mol Molar mass

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Find the molar mass of SnBr Practice A.1 mole of Br atoms B.1 mole of Sn atoms C.1 mole of SnBr formula units =79.90 g/mole = g/mole = g/mole

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Converting between mass, molar mass and moles m = quantity of matter (mass) in grams n = quantity of matter in moles M = molar mass m = n x M So if you wanted to know the mass of 2 mol of carbon m = (2 mol) x (12.01g/mol) or m = (2 mol) x (12.01g/mol) or 2 mol C | g C | 1 mole C | 1 mole C = g C

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Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl 2 = g/mol 1 mole Ca x 40.1 g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = g/mol CaCl 2 1 mole of N 2 O 4 = 92.0 g/mol Molar Mass of Molecules and Compounds

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A. Molar Mass of K 2 O = ? Grams/mole B. Molar Mass of antacid Al(OH) 3 = ? Grams/mole Al= 1*26.98 =26.98 O =3 *16. = 48.0 H= 3*1.008 = g/mol Practice

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Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. Practice

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Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al Converting Moles and Grams

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1. Molar mass of Al1 mole Al = 27.0 g Al 2. Conversion factors for Al 27.0g Al or 1 mol Al 27.0g Al or 1 mol Al 1 mol Al 27.0 g Al 1 mol Al 27.0 g Al 3. Setup3.00 moles Al | 27.0 g Al 1 mole Al Answer = 3.00* 27 g Al = 81.0 g Al

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The artificial sweetener aspartame (Nutra-Sweet) formula C 14 H 18 N 2 O 5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame? The artificial sweetener aspartame (Nutra-Sweet) formula C 14 H 18 N 2 O 5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame? Practice

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Atoms/Molecules and Grams Since 6.02 X particles = 1 mole AND 1 mole = molar mass (grams) You can convert atoms/molecules to moles and then moles to grams! (Two step process) You cant go directly from atoms to grams!!!! You MUST go thru MOLES. Thats like asking 2 dozen cookies weigh how many ounces if 1 cookie weighs 4 oz? You have to convert to dozen first!

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molar mass Avogadros number Grams Moles particles molar mass Avogadros number Grams Moles particles Everything must go through Moles!!! Calculations

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Atoms/Molecules and Grams How many atoms of Cu are present in 35.4 g of Cu? 35.4 g Cu 1 mol Cu 6.02 X atoms Cu 63.5 g Cu 1 mol Cu = 3.4 X atoms Cu

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Practice How many atoms of K are present in 78.4 g of K?

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Practice What is the mass (in grams) of 1.20 X molecules of glucose (C 6 H 12 O 6 )?

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Practice How many atoms of O are present in 78.1 g of oxygen? 78.1 g O 2 1 mol O X molecules O 2 2 atoms O 32.0 g O 2 1 mol O 2 1 molecule O 2

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22.4 L CO 1 mole CO.500 mol CO X L CO = = *Remember* 1 mol CO = 22.4 L CO *Remember* 1 mol CO = 22.4 L CO (1 mol CO )(X L CO )= (.500 mol CO )(22.4 L CO (1 mol CO ) X = 12.2 L of CO

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If you have a 35.67g piece of Chromium metal on your car, how many atoms of Chromium are in this piece of metal? If you have a 35.67g piece of Chromium metal on your car, how many atoms of Chromium are in this piece of metal? You are given mass and asked for number of particles Set it up as a factor label problem You are given mass and asked for number of particles Set it up as a factor label problemPracticePractice

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We are given a mass

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We are asked for atoms Its going to take us 2 conversions, we just need to follow the arrows

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1 st we must convert our given mass of Chromium to moles of Chromium1 st we must convert our given mass of Chromium to moles of Chromium –So we need to use the periodic table to calculate the mass of 1 mole of Chromium 1 st we must convert our given mass of Chromium to moles of Chromium1 st we must convert our given mass of Chromium to moles of Chromium –So we need to use the periodic table to calculate the mass of 1 mole of Chromium g Cr 1 mole Cr X mol Cr 35.67g Cr = = (51.996gCr)(X mol Cr) = (35.67gCr)(1 mol Cr) X =.6860 mol Cr

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2 nd we must convert our newly found moles of Cr to atoms of Cr2 nd we must convert our newly found moles of Cr to atoms of Cr –So we need to remember that 1 mole of anything there are 6.02x10 23 particles 2 nd we must convert our newly found moles of Cr to atoms of Cr2 nd we must convert our newly found moles of Cr to atoms of Cr –So we need to remember that 1 mole of anything there are 6.02x10 23 particles 6.02x10 23 atoms Cr 1 mole Cr X atoms Cr.6860 mol Cr = = (1 mol Cr)(X atoms Cr) = (6.02x10 23 atoms Cr) (.6860 mol Cr) (6.02x10 23 atoms Cr) (.6860 mol Cr) X = 4.13x10 23 atoms Cr

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Factor label one step method Given: 35.67g Cr Want: atoms Cr Conversions: 1 mole Cr = 6.02*10 atoms 1 mole Cr = 6.02*10 23 atoms 1 mole Cr = 1 mole Cr = g Cr Set up 35.67g Cr 1 mole Cr 6.02*10 atoms 1 mole Cr 35.67g Cr | 1 mole Cr |6.02*10 23 atoms | g Cr | 1 mole Cr = *1* 6.02*10 atoms= 2.148*10 25 atoms = 4.131*10 23 = *1* 6.02*10 23 atoms= 2.148*10 25 atoms = 4.131*10 23 atoms

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Percent Composition Atomic weights can be found by using the Periodic Table of the Elements. Find the atomic weight of each element. Multiply the number of atoms by the atomic weight, and add all of these weights per compound together. Divide each atom (or ion's) individual atomic mass by the total chemical mass *100

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Percent Composition FeO = Fe = g/mol O = g/mol FeO= ( )=

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Percent Composition FeO = Fe = g/mol / = g/mol / = = 0.223

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Percent Composition Fe = 0.777*100= % 0 = *100 = %

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Percent Composition Li 3 P - Lithium Phosphide Li = P = 1* = * = / = 0.598

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What is the percent carbon in C 5 H 8 NO 4 (the glutamic acid used to make MSG monosodium glutamate), a compound used to flavor foods and tenderize meats? a) 8.22 %C b) 24.3 %C c) 41.1 %C Percent Composition C=5*12.01 = H= 8*1.01 = N = 1*14.01 = O= 4* 16. =64.0 C 5 H 8 NO 4 = C= / = *100 = 41.1%

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Chemical Formulas of Compounds Formulas give the relative numbers of atoms or moles of each element in a formula unit - always a whole number ratio (the law of definite proportions). NO 2 2 atoms of O for every 1 atom of N NO 2 2 atoms of O for every 1 atom of N 1 mole of NO 2 : 2 moles of O atoms to every 1 mole of N atoms If we know or can determine the relative number of moles of each element in a compound, we can determine a formula for the compound.

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Types of Formulas Empirical Formula The formula of a compound that expresses the smallest whole number ratio of the atoms present. Ionic formula are always empirical formula Molecular Formula The formula that states the actual number of each kind of atom found in one molecule of the compound.

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Simplest and molecular formulae 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 formulas. Covalent compounds can either be molecular formulas (I.e. H 2 O 2 ) or simplest (e.g. HO) H O O H H O O H H O O H

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Simplest and molecular formulae Consider NaCl (ionic) vs. H 2 O 2 (covalent) Cl Na Cl Na 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 H O O H H O O H H O O H

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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 cant form a molecule - recall Lewis diagrams) NaCl is simplest (its ionic, thus it doesnt form molecules; it has no molecular formula) CHCH 2 OC4H7C4H7

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To obtain an Empirical Formula 1.Determine the mass in grams of each element present, if necessary. 2.Calculate the number of moles of each element. 3.Divide each by the smallest number of moles to obtain the simplest whole number ratio. 4. If whole numbers are not obtained * (in step 3), multiply through by the smallest number that will give all whole numbers * Be careful! Do not round off numbers prematurely

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A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine a formula for this substance. require mole ratios so convert grams to moles moles of N = 2.34g of N = moles of N g/mole g/mole moles of O = 5.34 g = moles of O g/mole g/mole Formula: Formula:

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A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine a formula for this substance. moles of N moles of O /0.167=1 /0.167 =2 N1O2N1O2 NO 2

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Empirical Formula from % Composition A substance has the following composition by mass: % Na ; % B ; % H What is the empirical formula of the substance? Na = g B = g H = g / = / = / = / 2.645= 1 / 2.645= 1 / 2.645= =4 NaBH 4

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Calculation of the Molecular Formula Molecular formula is actual formula of the compound. To determine the molecular formula from the empirical formula you must have the mass of the molecular formula. (Always Given to you) Divide the mass of molecular formula by the mass of the empirical formula. This will give you a whole number that you must multiply the subscripts in the empirical formula by.

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Calculation of the Molecular Formula CHO is the empirical formula for a compound with a molecular mass of g. CH 2 O is the empirical formula for a compound with a molecular mass of g. CHO = = 30.02g/mol CH 2 O = = 30.02g/mol Divide by /30.03 = 6 6 (CHO) = C 6 H 12 O 6 6 (CH 2 O) = C 6 H 12 O 6

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Calculation of the Molecular Formula A compound has an empirical formula of NO 2. The colourless liquid, used in rocket engines has a molar mass of 92.0 g/mole. What is the molecular formula of this substance? N2O4N2O4

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A compound contains 0.80 mol C, 4.0 moles H and 1.60 mol O, and 0.80 mol of N, and has a molecular mass of g/mol. What is the molecular formula for the compound? A compound contains 0.80 mol C, 4.0 moles H and 1.60 mol O, and 0.80 mol of N, and has a molecular mass of g/mol. What is the molecular formula for the compound? CO 2 H 5 N = Empirical CO 2 H 5 N = g/mol / = 4 4(CO 2 H 5 N) = C 4 O 8 H 20 N 4

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