What Is a Mole?

One mole = 6.022 x 1023 items

A mole of atomsOr molecules

How Big is a Mole?

• N=6.022x1023

• 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 (C6H12O6) (molar mass 180 g/mol)?

Balancing Chemical Equations2H2 + O2 2H2O

2 atoms hydrogen forms 2 molecules+ water

1 atom oxygen

Law of Conservation of Matter

Matter can not be created nor destroyed.2H2 + O2 2H2O

So 2 grams of hydrogen + 1 gram of oxygen does not form 2 grams of water

Balancing chemical equationsthe OHO method

O - OtherH- HydrogenO- Oxygen

Combustion reactions

• Balance the following reactions

• Methane + oxygen carbon dioxide and water

• Methanol (CH3OH) 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 A Moles B

Grams A Moles A Moles B

Grams A Moles A Moles B 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 KClO3 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

CH4(g) + 2 O2(g) ® CO2(g) + 2 H2O(g)• Our balanced equation for the combustion of

methane implies that every 1 molecule of CH4 reacts with 2 molecules of O2

H

HC

H

H+

O

O

C +OO

OO

+

OH H

OH H

+

Limiting and Excess Reactants in the Combustion of Methane

• CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)

• If we have 5 molecules of CH4 and 8 molecules of O2, which is the limiting reactant?

H

HC

H

H

+

OO

OO

OO

OO

OO

OO

OO

OO

?H

HC

H

H

H

HC

H

H

H

HC

H

H H

HC

H

H

ICE Chart

MOLES CH4 O2 CO2 H2O

Initial

Change

End

CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)

Stoichiometry (sample problems)• 3 CS2 + 6 NaOH 2 Na2CS3 + Na2CO3 + 3 H2O

• If 1.00 mol of CS2 reacts with 1.00 mol NaOH how many moles of each product are formed?

• How many grams of Na2CS3 are produced in the reaction of 88.0 mL of liquid CS2 (d=1.26g/mL) and 3.12 mol NaOH

Stoichiometry(sample problems)

• What mass of H2 is produced by the reaction of 2.14 g Al with 75.0 mL of 2.90 M HCl?

• 2 Al + 6HCl 3H2 + 2 AlCl3

Percent yield

Percent yield

• Chlorobenzene, a starting material in the production of aspirin and other compounds is prepared from benzene by the following reaction

• C6H6(l) + Cl2(g) C6H5Cl(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 C4H9Br, 21.6 g

NaBr, and 33.8 g H2SO4 as reactants in this reaction

• C4H9Br + NaBr + H2SO4 C4H9Br + NaHSO4 + H2O

• A student following these directions obtains 16.8 g C4H9Br. What are (a) the theoretical yield (b) the actual yield and (c) the percent yield in the reaction?