What Is a Mole?

One mole = 6.022 x 10 23 items A mole of atoms Or molecules

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 • Moles to molecules or atoms • Use Molar Mass • Use Avogadro’s number • Ex: How many moles are in 9.01 g of water?

• 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 + 1 atom oxygen forms 2 molecules water

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  water carbon dioxide and • 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

Grams A Grams A Stoichiometry Moles A Moles B Moles A Moles B Moles B Moles A Grams 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 solid KCl and gaseous oxygen. How many moles of KCl will be produced?

3 decomposes to give

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 with 2 molecules of O 2 reacts H H H C H + O O + O O O C O + H + O O H H H

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 H H H C H H C H H H H C H H H H H C H H + O O O O O O O O O O O O O O O O ?

MOLES

Initial Change End ICE Chart CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g )

CH 4 O 2 CO 2 H 2 O

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

Percent yield

Percent yield • 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 NaHSO 4  C 4 H + H 2 O 9 Br + • 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?