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Ch 7New.notebook October 31, 2012 THE MOLE!!! 1 Ch 7New.notebook October 31, 2012 23 representative particles of • a mole (mol) of a substance represents 6.02 X 10 that substance. chemical • The mole is a unit of measurement for the amount of substance or amount. It is one of the base units in the International System of Units, and has the unit symbol mol • What is means is that the mol is a word that stands for a number, like the word 23 dozen stands for the number 12. A mol of something has 6.02 X 10 representative particles of that substance. 2 Ch 7New.notebook October 31, 2012 1) One billion Pb atoms is how many mols of Pb? 1,000,000,000 Pb atoms 1 X 1 mol Pb = 1.66 X 10 15 mol Pb 23 6.02 X 1023 atoms Pb 3 Ch 7New.notebook October 31, 2012 2) How many Hydrogen atoms are in 0.5 moles of sucrose (C12 H22 O11) 0.5 mol C12H22O11 1 x 6.02 X 1023 molecules C12H22O11 1 mol C12H22O11 22 atoms of H x 1 molecule C H O 12 22 11 4 Ch 7New.notebook October 31, 2012 5 Ch 7New.notebook October 31, 2012 EX: What is the molar mass of the following: 1)Pb 2)NaCl 3)Water 4)Calcium chloride 5)C12 H22 O11 6) Tin (IV) phosphate 6 Ch 7New.notebook October 31, 2012 EX: What is the molar mass of the following: 1)Pb=207.2 2)NaCl23+35.45=58.45 3)WaterH2O 1+1+16=18 4)Calcium chloride CaCl2 40+2(35.45) =110.9 5)C12 H22 O11 12(12)+22(1)+11(16)=342 6) Tin (IV) phosphate Sn3(PO4)4 3(118.7)+4(30.97)+16(16)=735.98 7 Ch 7New.notebook October 31, 2012 8 Ch 7New.notebook October 31, 2012 The molar mass of something is the mass of 1.0 mol of that stuff in grams; just like adding up the atomic masses gives us the mass of just one of them in amu’s. That makes the unit of molar mass = g/mol (molar mass) 9 Ch 7New.notebook October 31, 2012 Name each of the following chemical compounds and list their molar masses to the nearest g/mol: 1) PbSO4 2) N2O3 3) CoCl2 . 4 H2O 4) B2F6 5) Sn(CO3)2 Write the formulas of each of the following chemical compounds and list their molar masses to the nearest g/mol: 6) copper (I) oxide 7) ammonium phosphate 8) vanadium (V) cyanide 9) nitrogen tribromide 10) iron (II) fluoride tetrahydrate 10 Ch 7New.notebook October 31, 2012 Name each of the following chemical compounds and list their molar masses to the nearest g/mol: 1) PbSO4 lead (II) sulfate303 g/mol 2) N2O3 dinitrogen trioxide76 g/mol 3) CoCl2 . 4 H2O cobalt (II) chloride tetrahydrate 202 g/mol 4) B2F6 diboron hexafluoride136 g/mol 5) Sn(CO3)2 tin (IV) carbonate239 g/mol Write the formulas of each of the following chemical compounds and list their molar masses to the nearest g/mol: 6) copper (I) oxide Cu2O143 g/mol 7) ammonium phosphate (NH4)3PO4 149 g/mol 8) vanadium (V) cyanide V(CN)5 181 g/mol 9) nitrogen tribromide NBr3 254 g/mol 10) iron (II) fluoride tetrahydrate FeF2 . 4 H2O166 g/mol 11 Ch 7New.notebook October 31, 2012 Review of Day 1 We now know two things: 1) There are 6.02 X 1023 particles in a mol 2) The molar mass gives us how many grams are in a mol 12 Ch 7New.notebook October 31, 2012 Review of Day 1 We now know two things: 1) There are 6.02 X 1023 particles in a mol 2) The molar mass gives us how many grams are in a mol So for water (for example): 6.02 X 1023 H2O molecules = 1 mol and 1 mol H2O = 18 g H2O 13 Ch 7New.notebook October 31, 2012 So... the molar mass of tin (IV) phosphate is 735.98 g/mol. That means 1 mol of tin (IV) phosphate has a mass of 735.98 g ...and if you have 735.98 g of tin (IV) phosphate you have 1 mol In dimensional analysis terms: 735.98 g Sn3(PO4)4 1 mol Sn3(PO4)4 both are legit conversion factors! (PO4)4 735.98 g Sn3(PO4)4 1 mol Sn3 14 Ch 7New.notebook October 31, 2012 Review of Day 1 We now know two things: 1) There are 6.02 X 1023 particles in a mol 2) The molar mass gives us how many grams are in a mol So for water (for example): 6.02 X 1023 H2O molecules = 1 mol and 1 mol H2O = 18 g H2O To that lets add one more tidbit: 1 mol of any gas at STP has a volume of 22.4 L 15 Ch 7New.notebook October 31, 2012 How many mols of water are in 47.9 g of water? How many molecules of water is that? How many molecules of water are in 47.9 g of water? (the above in one step) 16 Ch 7New.notebook One mole of X is: • 6.02 X 10 23 of X (in number) • Has a mass in grams = the molar mass of X • If X is a gas at STP has a volume = 22.4 L (grams) October 31, 2012 (L) • atoms • molecules • ions • formula units 17 Ch 7New.notebook October 31, 2012 Convert the following to mols: 1) 12. 8 g of sodium acetate 2) 8.0 L of dinitogen pentoxide gas at STP 3) 1.7 X1019 water molecules How many molecules and what is the mass of 150.0 mL of carbon dioxide at STP? 18 Ch 7New.notebook October 31, 2012 1) Convert the following to moles: a) 1.6 L of dinitrogen pentoxide gas at STP b) 43.8 g of copper metal c) 2.87 X 10 23 atoms of lead d) 19.4 g of calcium carbonate e) 45,235 ml of neon gas at STP 19 Ch 7New.notebook October 31, 2012 2) How many carbon dioxide molecules are in 6.70 g of carbon dioxide? 3) How many L of volume would 5.6 g of nitrogen gas (N2) at STP occupy? 4) If every cat in the world (11.2 billion of the beasts) was reduced to 1 carbon atom per cat (thus 11.2 billion C atoms) how many grams of carbon would they make? 20 Ch 7New.notebook October 31, 2012 5) How many ammonium ions are in .0000536 g of ammonium phosphate? 6) What is the mass of air (roughly 79% N2 and 21% O2 ) in a 55 gallon drum at STP? (1 gal = 3.785 L)(even though there is no “air” molecule air can be given an average molecular mass based on it’s percent composition) 21 Ch 7New.notebook October 31, 2012 Percent Composition • Percent composition tells us the percent by mass of each element within an element We calculate this by: grams of the element X 100 % grams of the compound if we’re not given grams we use 1 mol of the stuff so we can use the molar mass EX: What is the % composition of nitric acid? 1) What is nitric acid? HNO3 2) What is its molar mass? 1 + 14 + 3(16) = 63 g/mol 3) Calculate: % H = 1/63 = .0159 = 1.59 % H % N = 14/63 = .222 = 22.2 % N % O = [3(16)] / 63 = .762 = 76.2 % O we could check by adding up and getting close to 100% What is the % composition of calcium acetate? 22 Ch 7New.notebook October 31, 2012 Percent Composition • Percent composition tells us the percent by mass of each element within an element We calculate this by: grams of the element X 100 % grams of the compound if we’re not given grams we use 1 mol of the stuff so we can use the molar mass EX: What is the % composition of nitric acid? 1) What is nitric acid? HNO3 2) What is its molar mass? 1 + 14 + 3(16) = 63 g/mol 3) Calculate: % H = 1/63 = .0159 = 1.59 % H % N = 14/63 = .222 = 22.2 % N % O = [3(16)] / 63 = .762 = 76.2 % O we could check by adding up and getting close to 100% What is the % composition of calcium acetate? % Ca = 40/158 = .253 = 25.3% % C = 48/158 = .304 = 30.4% % H = 6/158 = .038 = 3.8% % O = 64/158 = .405 = 40.5% 23 Ch 7New.notebook October 31, 2012 • Another way we find % composition is by experiment In an experiment 0.500 g of an acid was analyzed. It was found to be 0.010 g H, 0.163 g S, and 0.327 g O. What is the acid’s % composition? 24 Ch 7New.notebook October 31, 2012 • Another way we find % composition is by experiment In an experiment 0.500 g of an acid was analyzed. It was found to be 0.010 g H, 0.163 g S, and 0.327 g O. What is the acid’s % composition? % H = .01/.5 = .02 = 2% % S = .163/.5 = .326 = 32.6% % O = .327/.5 = .654 = 65.4% 25 Ch 7New.notebook October 31, 2012 Determining Empirical and Molecular formulas • Before we go into the math of this we have to define these two things: • Empirical formula: the lowest whole number ratio of the atoms in a compound • Molecular formula: the actual number of atoms in the compound 26 Ch 7New.notebook October 31, 2012 We can use % composition data to find empirical formulas EX: What is the empirical formula of a compound that is 79.8 % C, and 20.2 % H 1) assume you have 100 g of the compound that means you would have 79.8 g of C and 20.2 g of H 2) convert these to moles 79.8 g of C 1 mole of C = 6.65 mol 1 X 12 g of C of C 20.2 g of H 1 mole of H = 20.2 mol 1 X 1 g of H of H 3) divide by the smallest of the mole numbers 6.65 mol of C = 1 mol of C 6.65 20.2 mol of H = 3 mol of H 6.65 therefore the EF is: CH3 27 Ch 7New.notebook October 31, 2012 what if we don’t get whole numbers when we divide? • if it’s close to a whole number it probably is that number (4.06 = 4) • all the numbers may need multiplied by a whole number to become whole. EX : C = 2.3, H = 3, N = 1 X 3 to get C 7H9N3 Try finding the empirical formula for the acid in the previous part 28 Ch 7New.notebook October 31, 2012 what if we don’t get whole numbers when we divide? • if it’s close to a whole number it probably is that number (4.06 = 4) • all the numbers may need multiplied by a whole number to become whole. EX : C = 2.3, H = 3, N = 1 X 3 to get C 7H9N3 Try finding the empirical formula for the acid in the previous part H = 2%, S = 32.6%, O = 65.4% 2 g H 1 mol H 1 1 g H 2 mol H / 1.017 = 1.96 2 32.6 g S 1 mol S 1.017 mol S / 1.017 = 1 1 32.06 g S 65.4 g O 1 mol O 4.088 mol O / 1.017 = 4.02 1 16 g O 4 29 Ch 7New.notebook October 31, 2012 Finding molecular formulas: • To find molecular formulas(MF) from empirical formulas(EF) we need another piece of information. The compounds molecular mass(MM) • If we found a compounds EF to be CH 3 and we also know its MM to be 30 Add up the weight of the EF CH 3 = 15 Find how many times that goes into the compounds MM 30/15 = 2 Multiply the EF through by that number to get the MF CH3 X 2 = C2H6 30 Ch 7New.notebook October 31, 2012 Summary Problem: 1,6 diaminohexane is used to make nylon. Analysis of this compound finds its percent composition to be 62.1% C, 13.8% H, and 24.1% N. Its molecular mass is also found to be 116 g/mol. What are the empirical and molecular formulas of this compound? 31 Ch 7New.notebook October 31, 2012 Summary Problem: 1,6 diaminohexane is used to make nylon. Analysis of this compound finds its percent composition to be 62.1% C, 13.8% H, and 24.1% N. Its molecular mass is also found to be 116 g/mol. What are the empirical and molecular formulas of this compound? 32 Ch 7New.notebook October 31, 2012 33 Attachments solid_atoms.swf