Stoichiometry Milwaukie High School. Notes One Unit 4 Making Cookies Making Chemicals Stoichiometry...

Stoichiometry

Milwaukie High School

Notes One Unit 4

Making CookiesMaking ChemicalsStoichiometryMoles-Moles CalculationA 401, A 402A

Read pgs 343-352

Making Cookies

Making CookiesWhat does the following recipe tell us?1 C butter +1 C sugar +2 egg yolks +1/4 C vegetable oil +1/2 C cocoa + 2 tsp vanilla + 2-1/4 C flour + 1/4 tsp salt +1 C Chocolate Powder + 4 Oz semisweet chocolate, 2 TBS cream 32 Mud Puddle CookiesHow many cookies can be made with…

64 cookies 160 cookies 4 cups of sugar and 1 Egg?128 cookies 16 cookies1-1/8 of C flour and 8 cups of oil?16 cookies 1024 cookies8 Cookies_____ cups butter?0.25

24 Cookies_____ tsp vanilla?1.564 Cookies_____ egg yolks?4

2 cups of butter and 10 eggs?

Making Chemicals

StoichiometryStoichiometry

Consider the chemical equation:4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

There are several numbers involved. What do they all mean?

““stoichio” = Greek for elementstoichio” = Greek for element““metry” = measurementmetry” = measurement

Stoichiometry is about measuring the amounts of Stoichiometry is about measuring the amounts of elements and compounds involved in a reaction. elements and compounds involved in a reaction.

Quantitative study of reactants and products in chemical reactions.


Recall that Chemical formulas represent numbers of atoms4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

NH3 1 nitrogen and 3 hydrogen atoms

O2 2 oxygen atoms

H2O 2 hydrogen atoms and 1 oxygen atom

NO 1 nitrogen atom and 1 oxygen atom


Recall that Chemical formulas have molar masses:

4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

NH3 17.0 g/mol

O2 32.0 g/mol

H2O 18.0 g/mol

NO 30.0 g/mol

***To find the molar mass of a chemical formula – add the atomic masses of theelements forming the compound. Use the periodic table to determine the atomicmass of individual elements.***

StoichiometryStoichiometryRecall that Chemical formulas are balanced with coefficients

4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

4 X NH3 = 4 nitrogen + 12 hydrogen

5 X O2 = 10 oxygen

6 X H2O = 12 hydrogen + 6 oxygen

4 X NO = 4 nitrogen + 4 oxygen


With Stoichiometry we find out that 4 : 5 : 6 : 4

do more than just multiply atoms.

4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

4 : 5 : 6 : 4Are what we call a mole ratio.

StoichiometryStoichiometry4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

4 : 5 : 6 : 4Can mean either:

4 molecules of NH3 react with 5 molecules of O2

to produce 6 molecules of H2O and 4 molecules of NO

OR4 moles of NH3 react with 5 moles of O2

to produce 6 moles of H2O and 4 moles of NO

StoichiometryStoichiometry Example (1) Example (1)moles of reactants moles of products

A reaction takes place between Lithium and water:Li(s) + H2O (l) LiOH(aq) + H2 (g)

Question: How many moles of H2 will be formed if 6.23 moles of Li combine with water?

StoichiometryStoichiometry Example (1) Continued Example (1) ContinuedQuestion: How many moles of H2 will be formed if 6.23 moles of Li combine with water?

1. Balance the equation using coefficients2Li(s) + 2 H2O (l) 2 LiOH(aq) + 1H2 (g)

2. Convert the required amount to moles *do not need this step for this question*

6.23 moles of Li (from question)

StoichiometryStoichiometry Example (1) Continued Example (1) ContinuedQuestion: How many moles of H2 will be formed if 6.23 moles of Li combine with water?

3. Find the mole ratio using the coefficients.2Li(s) + 2 H2O (l) 2 LiOH(aq) + 1 H2 (g)

2 moles of Li = 1 mole H2

4. Convert to desired unit The question asked for moles so 3.12 moles H2

doesn’t need to be converted and is the final answer.

22 H mol 3.12

Li mol 2H mol 1Li mol 6.23

4NH3 + 5O2 6H2O + 4NO

How many moles of H2O are produced if 2.00 moles of O2 are used?

Stoichiometry Question (1)Stoichiometry Question (1)

2.00 mol O2 2.40 mol H2O=

Notice that a correctly balanced equation is essential to get the right answer

6 mol H2O

5 mol O2

4 mol NO 6 mol H2O

4 NH3 + 5 O2 6 H2O + 4 NO

How many moles of NO are produced in the reaction if 15 mol of H2O are also produced?

Stoichiometry Question (2)Stoichiometry Question (2)

15 mol H2O 10. mol NO=

Notes Two Unit Four

Mass-Mass CalculationA 402BGroup Assignment GA 402

Read pgs 343-352Do A403 during break!


Read the chemical equation:4NH4NH33 + 5O + 5O22 6H 6H22O + 4NOO + 4NO

““stochio” = Greek for elementstochio” = Greek for element““metry” = measurementmetry” = measurement

Stoichiometry is about measuring the amounts of Stoichiometry is about measuring the amounts of elements and compounds involved in a reaction. elements and compounds involved in a reaction.

Quantitative study of reactants and products in chemical reactions.

Balanced Equations Have RatiosBalanced Equations Have Ratios

The coefficients in a chemical equation can be interpreted as the ratio of molecules of each substance.

2 CO(g) + O2 (g) 2 CO2 (g)

The image and the Balance equation mean:2 molecules of CO reacts with 1 molecule of oxygen gas to generate 2 molecules of CO2

What Does The Ratio Mean?What Does The Ratio Mean?2 CO(g) + O2 (g) 2 CO2 (g)

If I have 6 moles of CO and 6 moles of O2 can I

make 6 moles of CO2? (HINT… think how many CO must reach with each O2?

6 moles CO(g) + 6 moles O2 (g)

RatioRatio 2 CO(g) + O2 (g) 2 CO2 (g)

I can’t make 6 moles of CO2 because for every one O2 mole I need 2 CO moles

That means I will run out of CO moles after I react with 3 O2 moles.

1 2 3

ResultsResults

6 molecules of CO create 3 molecules CO2

2 to 1 ratio

ResultsResults ContinuedContinued

6 molecules of O2 create 6 molecules CO2

1 to 1 ratio

Moving Along The Stoichiometry PathMoving Along The Stoichiometry Path

We always use the same type of information to make the jumps between steps:

grams (x) moles (x) moles (y) grams (y)

Molar mass of x Molar mass of y

Mole ratio from balanced equation

We can start anywhere along this path depending on the question we want to answer

** Notice we can’t directly convert from grams of one compound to grams of another. We must go through moles using the mole ratio.**

2 mol NH3 1 mol N2

14.0 g N2

17.0g NH3=

17.0 g NH3 1 mol NH3

1 mol N2 28.0 g N2

Mass-Mass Calculation (1)Mass-Mass Calculation (1)

How many grams of ammonia will be made reacting with 14.0 grams of nitrogen reaction with hydrogen? 1N2(g) + 3H2(g) 2NH3(l)

How many grams of hydrogen will be formed by a reaction of 80.5g of lithium with water? 2 Li(s) + 2 H2O (l) 2 LiOH(aq) + 1 H2 (g)

1 mol H2 2 mol Li

80.5 g Li

11.7 g H2=

2.0 g H2 1 mol H2

1 mol Li 6.9 g Li


How many grams of NO2 are formed by reacting 1.44 grams of NO with oxygen gas?

2NO(g) + O 2(g) → 2NO2(g)

2 mol NO2 2 mol NO

1.44 g NO

2.21 g NO2=

46.0 g NO2 1 mol NO2

1 mol NO 30.0 g NO


Have We Learned It Yet?Have We Learned It Yet?Try these on your own - 4 NH3 + 5 O2 6 H2O + 4 NO

a) How many moles of H2O can be made using 1.6 mol NH3?

b) How many grams of NO can be made from 47 g of NH3?

4 NH3 + 5 O2 6 H2O + 4 NO

a)

b)

AnswersAnswers

6 mol H2O 4 mol NH3

1.6 mol NH3 2.4 mol H2O=

4 mol NO 4 mol NH3

47 g NH3

83 g NO=

30.0 g NO 1 mol NO

1 mol NH3 17.0 g NH3

Let’s Put All The Steps Together!Let’s Put All The Steps Together!

Factor label Method: it uses UNITS to cancel and work your way through the problem

Given Info (g) 1 Mole Given (mol) Moles Requested MM Requested (g) of Requested (g) MM Given (g) Moles Given 1 Mole Requested =

Given Requested Mole to Mole

The given converts grams of given to moles of given. The middle converts moles of given to moles of requested.The requested converts moles of requested to grams of requested.All in one multistep process !!! THIS IS A MASS MASS PROBLEM.

Notes Three Unit FourCA 401 Mass-Mass Calculations

ChemistryChemistryPurgatory

Purgatory

Remember Stoich??

Steps To Follow StoichSteps To Follow Stoich

8 mol CO2 1 mol C8H8

6.00 g C8H8

20.3 g CO2=

44.0 g CO2 1 mol CO2

1 mol C8H8 104.0 g C8H8

Mass-Mass Calculation (4)Mass-Mass Calculation (4)How many grams of carbon dioxide will be made by burning 6.00 grams of Isovanillin? 1C8H8(l)+ 15O2(g) 8 CO2(g) + 4 H2O(g)

4 mol Ag 2 mol AgO

8.00 g AgO

7.45 g Ag=

107.9 g Ag 1 mol Ag

1 mol AgO 231.8 g AgO

Mass-Mass Calculation (5)Mass-Mass Calculation (5)How many grams of silver will be made by decomposing 8.00 grams of Silver oxide? 2Ag2O(s) 1O2(g)+ 4Ag(s)

Notes Four Unit FourLimiting Reactant Mass-Mass ProblemMolar Volume Mass-Volume Problem

Limiting Reactants

If the moles of the reactants exactly matches the molar ratio, then both reactants are completely consumed

Otherwise, one of the reactants is only partially consumed

The reactant that is used up is called the limiting reactant, since it is the one that stops the reaction

2 mol NH3 1 mol N2

14.0 g N2

17.0 g NH3

=


1 mol N2 28.0 g N2

Determining Limiting ReactantDetermining Limiting ReactantHow many grams of ammonia will be made reacting with 14.0 grams of nitrogen with 7.0 g of hydrogen? 1N2(g) + 3 H2(g) 2NH3(l)

3 mol H2 2 mol NH3

7.0 g H2

89.3 g NH3=


1 mol H2 2.0 g H2

Nitrogen Is the Limiting Reactant

1 mol C6H4Cl2 1 mol C6H6

24.0 g C6H6

126 g C6H4Cl2=

147.0 g C6H4Cl2 1 mol C6H4Cl2

1 mol C6H6 28.0 g C6H6

Limiting Reactant ProblemLimiting Reactant ProblemHow many grams of C6H4Cl2(s) will be made reacting 24.0 grams of benzene with 77.0 g of chlorine?

1 mol C6H4Cl2 2 mol Cl2

77.0 g Cl2

159 g C6H4Cl2=

147.0 g C6H4Cl2 1 mol C6H4Cl2

1 mol Cl2 71.0 g Cl2

Benzene C6H6 Is the Limiting Reactant

1C6H6(l) + 2Cl2(g) 1 C6H4Cl2(s) + 2HCl(g)

Molar Volume @STP

1molN2(g) = 28.0g/mol 22.4L/mol

1molO2(g) = 32.0g/mol 22.4L/mol1molAr(g)= 39.9g/mol 22.4L/mol

2 mol NH3 1 mol N2

56.0 g N2

89.6 l NH3=

22.4 l NH3 1 mol NH3

1 mol N2 28.0 g N2

Mass-Volume Calculation Mass-Volume Calculation How many liters of ammonia will be made reacting 56.0 grams of nitrogen with hydrogen @ STP? 1N2(g) + 3 H2(g) 2 NH3(l)

2 mol NH3 1 mol N2

33.6 l N2

67.2 l NH3=

22.4 l NH3 1 mol NH3

1 mol N2 22.4 l N2

Volume-Volume Calculation Volume-Volume Calculation How many liters of ammonia will be made reacting 33.6 liters of nitrogen with hydrogen @STP? 1N2(g) + 3 H2(g) 2NH3(l)

18.0 g H2O 1 mol H2O

6 mol H2O 4 mol NH3

4 NH3 + 5 O2 6 H2O + 4 NO

How many grams of H2O are produced if 2.2 mol of NH3 are combined with excess oxygen?

Stoichiometry Question (3)

2.2 mol NH3 59 g H2O

=

5 mol O2 6 mol H2O

32.0 g O2 1 mol O2

4 NH3 + 5 O2 6 H2O + 4 NO

How many grams of O2 are required to produce 0.3 mol of H2O?


0.3 mol H2O 8 g O2=

4 NH3 + 5 O2 6 H2O + 4 NO

How many grams of NO is produced if 12 g of O2 is combined with excess ammonia?

4 mol NO 5 mol O2


12 g O2

9.0 g NO=

30.0 g NO 1 mol NO

1 mol O2 32.0 g O2

Have we learned it yet?Try these on your own - 4 NH3 + 5 O2 6 H2O + 4 NO

a) How many moles of H2O can be made using 1.6 mol NH3?

b) What mass of NH3 is needed to make 0.75 mol NO?

c) How many grams of NO can be made from 47 g of NH3?

4 NH3 + 5 O2 6 H2O + 4 NO

a)

b)

c)

Answers

6 mol H2O 4 mol NH3

1.6 mol NH3 2.4 mol H2O

=

4 mol NH3

4 mol NO 0.75 mol NO 13 g

NH3=

17.0 g NH3

1 mol NH3

4 mol NO 4 mol NH3

47 g NH3

83 g NO=

30.0 g NO 1 mol NO

1 mol NH3 17.0 g NH3

Stoichiometry Milwaukie High School. Notes One Unit 4 Making Cookies Making Chemicals Stoichiometry...

Documents

Transcript of Stoichiometry Milwaukie High School. Notes One Unit 4 Making Cookies Making Chemicals Stoichiometry...