CHEM 5013 CHEM 5013 Applied Chemical Applied Chemical

PrinciplesPrinciples

Chapters Three and Four (Mole Chapters Three and Four (Mole Concepts)Concepts)

Professor BensleyProfessor BensleyAlfred State CollegeAlfred State College

Chapter ObjectivesChapter Objectives Explain the concept of a mole in your own Explain the concept of a mole in your own

words. words. Interpret chemical equations in terms of Interpret chemical equations in terms of

both moles and molecules.both moles and molecules. Interconvert between mass, number of Interconvert between mass, number of

molecules, and number of moles.molecules, and number of moles. Determine a chemical formula from Determine a chemical formula from

elemental analysis (i.e., from % elemental analysis (i.e., from % compositions).compositions).

Chapter ObjectivesChapter Objectives Define the concentration of a solution and Define the concentration of a solution and

calculate the molarity of solutions from calculate the molarity of solutions from appropriate data.appropriate data.

Calculate the molarity of solutions prepared by Calculate the molarity of solutions prepared by dilution or calculate the quantities needed to carry dilution or calculate the quantities needed to carry out a dilution to prepare a solution of a specified out a dilution to prepare a solution of a specified concentration.concentration.

Calculate the amount of product expected Calculate the amount of product expected from a chemical reaction, given the from a chemical reaction, given the amounts of reactants used.amounts of reactants used.

Chapter ObjectivesChapter Objectives

Calculate the amounts of reactants Calculate the amounts of reactants needed in a chemical reaction to needed in a chemical reaction to produce a specified amount of product.produce a specified amount of product.

Identify a limiting reagent and calculate Identify a limiting reagent and calculate the amount of product formed from a the amount of product formed from a nonstoichiometric mixture of reactants.nonstoichiometric mixture of reactants.

Calculate the percentage yield of a Calculate the percentage yield of a chemical reaction.chemical reaction.

Molecular WeightMolecular Weight

Remember atomic weight? Remember atomic weight? Molecular Weight –

Expressed in Expressed in amu

Example: HExample: H22O O

Formula WeightFormula Weight

Formula weight:Formula weight:

Formula weight (FW) covers both Formula weight (FW) covers both ionic and molecular compoundsionic and molecular compounds

NaCl: FW = NaCl: FW =

ExamplesExamplesCalculate the Calculate the formula weight formula weight of the of the

following compounds to 3 sig figs:following compounds to 3 sig figs:

1.1. Calcium hydroxide Calcium hydroxide

2.2. Methylamine CHMethylamine CH33NHNH22

The MoleThe Mole

A A mole is:is:

A.

B.

C.

D.

A chemical mass unit, defined

to be 6.022 x 1023 molecules,

atoms, or some other unit.

The Mole The Mole

You have one car.You have one car.How many engines do you have?How many engines do you have?How many wheels do you have?How many wheels do you have?

You have 1 dozen cars.You have 1 dozen cars.How many engines do you have? How many engines do you have? How many dozens of engines do you have? How many dozens of engines do you have? How many wheels do you have?How many wheels do you have?How many dozens of wheels do you have? How many dozens of wheels do you have?

You have 1 mole of cars. (1 Chemist’s Dozen)You have 1 mole of cars. (1 Chemist’s Dozen)How many engines do you have?How many engines do you have?How many moles of engines do you have?How many moles of engines do you have?How many wheels do you have?How many wheels do you have?

How many moles of wheels do you have?How many moles of wheels do you have?

12 x

6.02 x 1023 x

The MoleThe Mole

You have one molecule of CClYou have one molecule of CCl44..How many Carbon atoms do you have?How many Carbon atoms do you have?How many Chlorine atoms do you have?How many Chlorine atoms do you have?

You have 1 dozen molecules of CClYou have 1 dozen molecules of CCl44..How many Carbon atoms do you have?How many Carbon atoms do you have?How many dozen Carbon atoms do you have?How many dozen Carbon atoms do you have?How many Chlorine atoms do you have?How many Chlorine atoms do you have?How many dozen Chlorine atoms do you have?How many dozen Chlorine atoms do you have?

You have 1 mole of CClYou have 1 mole of CCl44. (Chemist’s Dozen). (Chemist’s Dozen)How many Carbon atoms do you have? How many Carbon atoms do you have? How many moles of Carbon atoms do you have? How many moles of Carbon atoms do you have? How many Chlorine atoms do you have?How many Chlorine atoms do you have?How many moles of Chlorine atoms do you have?How many moles of Chlorine atoms do you have?

12 x

6.02 x 1023 X

The MoleThe Mole

Example: One mole of NaExample: One mole of Na22COCO33 contains how many moles of Sodium contains how many moles of Sodium ions? How many actual sodium ions?ions? How many actual sodium ions?

How many moles of carbonate ions? How many moles of carbonate ions? How many actual carbonate ions? How many actual carbonate ions? Think of it as (COThink of it as (CO33))11

The MoleThe Mole

1 Mole of Oxygen atoms (O) contains 1 Mole of Oxygen atoms (O) contains how many O atoms?how many O atoms?

But 1 mole of Oxygen molecules (OBut 1 mole of Oxygen molecules (O22) ) contains how many O atoms? contains how many O atoms?

Molar MassMolar Mass

Molar mass:

What is molar mass of carbon-12? How What is molar mass of carbon-12? How many grams in one mole? many grams in one mole?

Molar massMolar mass in in grams per molegrams per mole is is numerically equal to the formula weight in numerically equal to the formula weight in amu.amu.

ExamplesExamples

How many How many moleculesmolecules of HNO of HNO33 are present in 2.5 moles HNOare present in 2.5 moles HNO33??

What is the mass in grams of What is the mass in grams of one nitric acid molecule, HNOone nitric acid molecule, HNO33??

Mole CalculationsMole Calculations

Two VERY important mole calculations:Two VERY important mole calculations:

1.1. How much does a given number of How much does a given number of moles of a substance weigh? moles of a substance weigh? (convert (convert moles to gramsmoles to grams))

2.2. Also, how many moles are in a given Also, how many moles are in a given mass of a substance?mass of a substance? (convert (convert grams to molesgrams to moles))

Mole CalculationsMole CalculationsA sample of nitric acid contains A sample of nitric acid contains

0.253 mol HNO0.253 mol HNO33. How many . How many grams is this?grams is this?

A mixture for an acid used on a construction project calls for 25 grams of Sulfuric Acid (H2SO4) to be used. How many moles of sulfuric acid is this?

Mole CalculationsMole Calculations

The formulation for a test batch of The formulation for a test batch of structural steel contains 0.05% structural steel contains 0.05% Silicon by mass. This calculates out Silicon by mass. This calculates out to 1.0x10to 1.0x10-6-6 gram for your gram for your formulation. How many atoms of formulation. How many atoms of Silicon were added to the batch to Silicon were added to the batch to produce the correct steel produce the correct steel formulation?formulation?

Determining Chemical Determining Chemical FormulasFormulas

Percent composition of a compound = of a compound =

Mass percentage:

# grams of A in 100 g of the whole thing

mass of A in the

wholeMass %A = 100 x mass of the whole

ExampleExample

Lead(II) chromate, PbCrOLead(II) chromate, PbCrO44 is is used as a paint pigment used as a paint pigment (yellow). What is the (yellow). What is the percentage composition of percentage composition of lead(II) chromate?lead(II) chromate?

ExampleExample

The chemical name of table The chemical name of table sugar is sucrose, Csugar is sucrose, C1212HH2222OO1111. . How many grams of carbon How many grams of carbon (C) are there in 61.8 grams of (C) are there in 61.8 grams of sucrose?sucrose?

Determining Chemical Determining Chemical FormulasFormulas

Empirical formula:

Example: HExample: H22OO22

ExampleExample

Sodium pyrophosphate is used Sodium pyrophosphate is used in detergent preparations. The in detergent preparations. The mass percentages of the mass percentages of the elements in this compound are elements in this compound are 34.6% Na, 23.3% P, 42.1% O. 34.6% Na, 23.3% P, 42.1% O. What is the empirical formula What is the empirical formula of sodium pyrophosphate?of sodium pyrophosphate?

Molecular Formula from Molecular Formula from Empirical FormulaEmpirical Formula

Molecular formula:Molecular formula:

Need 2 things to determine MF:Need 2 things to determine MF:

Molecular weight = n x empirical formula Molecular weight = n x empirical formula weightweight

So, n = So, n = molecular weight molecular weight empirical formula weightempirical formula weight

ExampleExample

Hexamethylene is one of the Hexamethylene is one of the materials used to produce a materials used to produce a type of nylon. Elemental type of nylon. Elemental analysis of the substance gives analysis of the substance gives 62.1% C, 13.8% H and 24.1% 62.1% C, 13.8% H and 24.1% N. Its molecular weight is 116 N. Its molecular weight is 116 amu. What is its molecular amu. What is its molecular formula?formula?

StoichiometryStoichiometry

Definition:Definition:

Based on:Based on:

StoichiometryStoichiometry

NN22 (g) + 3H (g) + 3H22 (g) (g) 2NH 2NH33 (g) (g)

NN22 molecules react with molecules react with

HH22 molecules to produce molecules to produce

NHNH33 molecules molecules

of Nof N22 reacts with reacts with

of Hof H22 to produce to produce

of NHof NH33

Stoichiometry Stoichiometry

NN22 (g) + 3H (g) + 3H22 (g) (g) 2NH 2NH33 (g) (g)

Because moles can be converted to grams, Because moles can be converted to grams, can also say:can also say:

How many grams of nitrogen will react with How many grams of nitrogen will react with 6.0 grams of hydrogen? 6.0 grams of hydrogen?

StoichiometryStoichiometry

The number of moles The number of moles involved in a reaction is involved in a reaction is

proportional to the proportional to the coefficients in the coefficients in the

balanced chemical balanced chemical equation!!!equation!!!

ExampleExample

How many moles of NHHow many moles of NH33 could we obtain from could we obtain from 3 moles of H3 moles of H22??

How many moles of NHHow many moles of NH33 could we obtain from could we obtain from 4.8 mol H4.8 mol H22??

)g(NH 2 (g)3H (g)N 322

StoichiometryStoichiometryCan also calculate problems Can also calculate problems

involving masses of reactants or involving masses of reactants or productsproducts

NN22 (g) + 3H (g) + 3H22 (g) (g) 2NH 2NH33 (g) (g)

How much hydrogen (in kg) is needed How much hydrogen (in kg) is needed to yield 907 kg of ammonia?to yield 907 kg of ammonia?

Grams of A

Conversion Factor: grams A to mol A

Conversion Factor: mol A to mol B

Conversion Factor: mol B to grams B

Grams of B

X

X

X

Flow Chart for ANY

Stoichiometry Problem

ExampleExample

How many grams of HCl are required How many grams of HCl are required to react with 5.00 grams of to react with 5.00 grams of manganese dioxide according to the manganese dioxide according to the equation?equation?

)s(MnO HCl(aq) 4 2 )g(Cl (aq)MnCl O(l)H 2 222

Limiting ReagentLimiting Reagent What happens when we don’t exactly What happens when we don’t exactly

follow the recipe?follow the recipe? Limiting reagent ––

What happens when the L.R. is used up?What happens when the L.R. is used up?

So what determines the number of So what determines the number of moles (amount) of product that we can moles (amount) of product that we can obtain in a reaction?obtain in a reaction?

Limiting ReagentLimiting Reagent

100 seats and 300 tires. How many 100 seats and 300 tires. How many bicycles can you make?bicycles can you make?

1 seat + 2 tires 1 seat + 2 tires 1 bicycle 1 bicycle

The The are the limiting reagent are the limiting reagent

Limiting ReagentLimiting Reagent

)g(H (aq)ZnCl HCl(aq) 2 Zn(s) 22

If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H2 are produced?

Limiting ReagentLimiting Reagent

Urea, CHUrea, CH44NN22O, is used as a nitrogen O, is used as a nitrogen fertilizer. It is manufactured from fertilizer. It is manufactured from ammonia and carbon dioxide. ammonia and carbon dioxide.

2NH2NH3 3 + CO+ CO22 CH CH44NN22O + HO + H22OO

10.0g NH10.0g NH33 and 10.0g CO and 10.0g CO22 are reacted are reacted together. What is the maximum together. What is the maximum quantity (in grams) of urea than can quantity (in grams) of urea than can be obtained? be obtained?

Theoretical YieldTheoretical Yield

Theoretical yield:

Percentage yield:

%100yield ltheoretica

yield actual Yield%

Working with SolutionsWorking with Solutions

Molar concentration or or Molarity

Molarity (M) =

Moles of soluteLiters of solution

MolarityMolarity

0.200 M (0.200 molar) solution of HCl is 0.200 M (0.200 molar) solution of HCl is how many moles of HCl dissolved in 1 how many moles of HCl dissolved in 1 liter of water? How many grams of HCl liter of water? How many grams of HCl dissolved in 1 liter of water?dissolved in 1 liter of water?

Example:Example:You place a 1.53 gram sample of potassium You place a 1.53 gram sample of potassium

dichromate, Kdichromate, K22CrCr22OO77, into a 50.0 mL , into a 50.0 mL volumetric flask and add water to bring the volumetric flask and add water to bring the solution up to the mark on the neck of the solution up to the mark on the neck of the flask. What is the molarity of the solution?flask. What is the molarity of the solution?

ExampleExample

A solution of sulfuric acid (HA solution of sulfuric acid (H22SOSO44) has a ) has a concentration of 0.154 M. concentration of 0.154 M.

How many moles of sulfuric acid are How many moles of sulfuric acid are

contained in a 500 mL bottle of the contained in a 500 mL bottle of the solution? solution?

How many grams of sulfuric acid are in How many grams of sulfuric acid are in the 500 mL solution?the 500 mL solution?

Diluting SolutionsDiluting Solutions

You have a 10 M solution You have a 10 M solution of HCl.of HCl.

Suppose however, you Suppose however, you want a 1 M solution. want a 1 M solution.

How do we make this 1 M How do we make this 1 M solution of HCl?solution of HCl?

Dilution formula Dilution formula derivationderivation

Diluting SolutionsDiluting Solutions

A stock solution of concentrated A stock solution of concentrated hydrochloric acid is 12.1M. How much hydrochloric acid is 12.1M. How much of this stock solution is needed to of this stock solution is needed to prepare 1.00 L of an aqueous solution, prepare 1.00 L of an aqueous solution, which is 0.25M HCl?which is 0.25M HCl?