How Big is a Mole? N=6.022x10 23 One mole of Marshmallows would cover the entire earth 12 miles high One mole of marshmallows would fill the Grand Canyon and still be enough left over to displace all the water from Lake Michigan and more
Moles as Conversion factors Grams to moles Use Molar Mass Ex: How many moles are in 9.01 g of water? Moles to molecules or atoms Use Avogadro’s number Ex: How many molecules of water are in 9.01 g of water?
Using Avogadro’s number Nicotine, a poisonous compound found in tobacco leaves, is 74.0% C, 8.65% H, and 17.35% N. It has a molar mass of 162 g/mol. What is the molecular formula of nicotine? The “average” cigarette in the US contains 9.0 mg of nicotine but during smoking about 90% of the nicotine is burned off. How many molecules of nicotine are inhaled during smoking of one “average” cigarette?
Molarity How would you prepare 1 liter of a 0.25 M (molar) solution of glucose (C 6 H 12 O 6 ) (molar mass 180 g/mol)?
Balancing Chemical Equations 2H 2 + O 2 2H 2 O 2 atoms hydrogen forms 2 molecules +water 1 atom oxygen
Law of Conservation of Matter Matter can not be created nor destroyed. 2H 2 + O 2 2H 2 O So 2 grams of hydrogen + 1 gram of oxygen does not form 2 grams of water
Balancing chemical equations the OHO method O - Other H- Hydrogen O- Oxygen
Combustion reactions Balance the following reactions Methane + oxygen carbon dioxide and water Methanol (CH 3 OH) burns in oxygen to form carbon dioxide and water
Balance the following chemical reactions Sodium sulfate and calcium nitrate react to form sodium nitrate and calcium sulfate Write a balanced equation for the reaction between aqueous solutions of potassium chromate and silver nitrate. The products of the reaction are solid silver chromate and a solution of potassium nitrate
Stoichiometry Moles AMoles B Grams AMoles AMoles B Grams AMoles A Moles BGrams B
Stoichiometry Mole to Mole Chlorine reacts with sodium to form sodium chloride. How many moles of sodium chloride are produced from 2.25 moles of chlorine? A 0.50 mol sample of solid KClO 3 decomposes to give solid KCl and gaseous oxygen. How many moles of KCl will be produced?
Stoichiometry mass to mass Phosphorus reacts with oxygen to produce diphosphorus pentoxide. What is the mass of product formed from 20.0 g phosphorus? Aluminum reacts with sulfur to produce aluminum sulfide. How many grams of sulfur are required to react with 4.80 grams of aluminum?
Limiting Reactant for reactions with multiple reactants, it is likely that one of the reactants will be completely used before the others when this reactant is used up, the reaction stops and no more product is made the reactant that limits the amount of product is called the limiting reactant – sometimes called the limiting reagent – the limiting reactant gets completely consumed reactants not completely consumed are called excess reactants the amount of product that can be made from the limiting reactant is called the theoretical yield
Put more simply: What is the theoretical yield of hamburgers in the above reaction?
Limiting and Excess Reactants in the Combustion of Methane CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O(g) Our balanced equation for the combustion of methane implies that every 1 molecule of CH 4 reacts with 2 molecules of O 2 H H C H H + O O C + OO OO + O HH O HH +
Limiting and Excess Reactants in the Combustion of Methane CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O(g) If we have 5 molecules of CH 4 and 8 molecules of O 2, which is the limiting reactant? H H C H H + OO OO OO OO OO OO OO OO ? H H C H H H H C H H H H C H H H H C H H
ICE Chart MOLESCH 4 O2O2 CO 2 H2OH2O Initial Change End CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O(g )
Stoichiometry (sample problems) 3 CS 2 + 6 NaOH 2 Na 2 CS 3 + Na 2 CO 3 + 3 H 2 O If 1.00 mol of CS 2 reacts with 1.00 mol NaOH how many moles of each product are formed? How many grams of Na 2 CS 3 are produced in the reaction of 88.0 mL of liquid CS 2 (d=1.26g/mL) and 3.12 mol NaOH
Stoichiometry(sample problems) What mass of H 2 is produced by the reaction of 2.14 g Al with 75.0 mL of 2.90 M HCl? 2 Al + 6HCl 3H 2 + 2 AlCl 3
Chlorobenzene, a starting material in the production of aspirin and other compounds is prepared from benzene by the following reaction C 6 H 6 (l) + Cl 2 (g) C 6 H 5 Cl(l) + HCl(g) benzene chlorobenzene A 10.0 kg sample of benzene treated with excess chlorine gas yields 10.4 kg of chlorobenzene. Calculate the % yield.
Actual and theoretical yields A laboratory manual calls for 13.0 g C 4 H 9 Br, 21.6 g NaBr, and 33.8 g H 2 SO 4 as reactants in this reaction C 4 H 9 Br + NaBr + H 2 SO 4 C 4 H 9 Br + NaHSO 4 + H 2 O A student following these directions obtains 16.8 g C 4 H 9 Br. What are (a) the theoretical yield (b) the actual yield and (c) the percent yield in the reaction?