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Teacher’s notes for class Concepts: Mole and its similarity to other things such as dozen, pounds in a ton. Dissimilarity to someone’s weight. Which has the most moles: 1 ton of steel or 1 feather? Which has the most mass? What is the difference between empirical formula and molecular formula? (Empirical smallest whole number mole ratio – molecular formula actually tells you how many number of atoms of each element in one molecule or formula unit of the substance – With certain numbers - the molar mass of acetylene for instance is 26.04 g/mol and the mass of the empirical formula of CH is 13.02 g/mol – if you divide the experimentally determined molar mass of acetylene by the empirical formula – 26.04 g/mol div. by 13.02 g/mol, you get 2 – that means that the actual molar mass of acetylene is two times the mass represented by the empirical formula. That means that the molecular formula of acetylene must contain two times the number of carbon atoms and twice the number of hydrogen atoms represented by the empirical formula. ***************** Mole-mass Conversions – 0 Determine the number of representative particles in each of the following – 35.3 mol carbon dioxide 0.425 mol nitrogen (N2) How many moles in 1.25 X 1025 copper (II) ions? How many molecules in 1.25 mol water? A bracelet contains 0.200 mol of metal atoms in 75 percent gold. How many particles of gold atoms are in the bracelet? *****************************8 Particle-mass conversions Convert the following to mass in grams – 1.22 X 1023 mol Ag (Silver) Calculate the number of atoms in 150 g Ar (Argon) ******************* Chemical formulas How many moles of oxygen atoms are in 2.50 mols Al2O3 – aluminum oxide? (A3+)l Number of moles is 2.50 Al2O3 Need number of moles of A3+) ions One mole of Al2O3 has 2 mols of aluminum ions One mole has how many mols of Oxyen? 2.50 mols Al2O3 x mols O/mols Al2O3 = mol O3 Molar Mass Determine the molar mass of nitric acid (HNO3) Get molar mass of each item and add them together to get the total H 1.0008 (1) N 14.007 (1) O 15.999 (3) Total all three is the answer Mass to mole conversions How many moles are in 100 g of dinitrogen oxide (N2O)? First get molar mass of dinitrogen oxide 2 mols of Nitrogen 1 mol of Oxygen Number of grams of dinitrogen oxide times 1 mol/your no of grams (100) = number of moles Fill in this table \ Compound Silver acetate Ag(C2H3O2) Glucose C6H12O6 Benzene C6H6 Lead (II) sulfide PbS Number of Moles Mass (g) Representative particles 2.50 324.0 5.65 x 1021 100.0 Percent composition Determine the empirical formula for each of the following: Ethylene (C2H4) Ascorbic Acid (C6H8O6) Naphthalene (C10H8) Vitamin E, found in many plants, is thought to retard the aging process in humans. The formula for vitamin E is C29H50O2. What is the percent composition of vitamin E? Take the mass of the element and divide it by the mass of the compound times 100 to get percent by mass So if you have 55 g of element X and divide it by 100 grams of the compound X 100 you have 55 percent of X. Etc. So first you get the total grams of the vitamin E and then you take each individual element and its mass and divide by the total grams times 100 – Misc. Which of the following has the greatest number of oxygen atoms? 17.63 g CO2 (Carbon dioxide) 2. 3.21 x 10 22 moles CH3OH (methanol) 3. 0.250 mol C6H12O6 (glucose) 1.