4. Balancing Reactions How are coefficients different from subscripts? 2H 2 + O 2 2H 2 O subscripts...

4. Balancing Reactions

How are coefficients different from subscripts?

2H2 + O2 2H2O

subscripts = # of atoms

4. Balancing ReactionsHow are coefficients different from subscripts?

2H2 + O2 2H2O

coefficients = how many


2H2 + O2 2H2O

subscripts = # of atomscoefficients = how many


H2 + O2 H2O2

subscripts = # of atomscoefficients = how many

New Unit: Stoichiometry

OBJECTIVE: Balancing Reactions + Grams Moles + Moles Grams

Topics to be Covered

1.What is Stoichiometry?

2.1 Step Conversions



5.Limiting Reactants

6.Percentage Yield

What is Stoichiometry?

▪ It is:–The QUANTITATIVE relationships between reactants and products–Using MATH and NUMBERS to calculate reactants and products

1. What is Stoichiometry?

1. What is StoichiometryBalance

d Reactions are

like

recipes

1. What is Stoichiometry

What informati

on is missing??

butter brown sugar egg flour baking soda salt

+ chocolate chips cookies

1. What is StoichiometryWhat

information Is

missing??

3/4 butter 1/2 brown sugar 1 egg 1 1/2 flour 1 baking soda 1/4 salt

+ 1 chocolate chips

30 cookies

1. What is StoichiometryBalance

d Reactions are

like

recipes

3/4 cup butter 1/2 cup brown sugar 1 egg 1 1/2 cups flour 1 teaspoon baking

soda 1/4 teaspoon salt

+ 1 cup chocolate chips

30 cookies

Fundamental MeasurementsWhat we measure UNIT

▪ Distance

▪ Mass

▪ Time

▪ Electric current

▪ Temperature

▪ Amount

▪ Intensity of light

▪ Meter

▪ Gram

▪ Seconds

▪ Amps

▪ Kelvin

▪ Mole

▪ Candela

Fundamental MeasurementsWhat we measure UNIT

▪ Distance

▪ Mass

▪ Time

▪ Electric current

▪ Temperature

▪Amount▪ Intensity of

light

▪ Meter

▪ Gram

▪ Seconds

▪ Amps

▪ Kelvin

▪Mole▪ Candela


KI + Pb(NO3)2 PbI2 + KNO3


2KI + Pb(NO3)2 PbI2 + 2KNO3

COEFFICIENTS = amount of MOLESKI = 2 moles

Pb(NO3)2 = 1 mole

PbI2 = 1 mole

KNO3 = 2 moles


2KI + Pb(NO3)2 PbI2 + 2KNO3

Stoichiometry = using coefficients from balanced reactions to convert grams

moles

and much more.

2. 1 Step Conversions

OBJECTIVE: Use stoichiometry to solve calculation problems


2H2 + O2 2H2O

You have 3 moles of O2

How many moles of H2O can you produce?

How do you solve something like this?


2H2 + O2 2H2O


1. Balance Reaction first!!!

2. Sideways T and MOLE RATIO

1. 2Na + Cl2 2NaCl5 moles of Na = ? moles NaCl?

2. CH4 + 2O2 CO2 + 2H2O2 moles of CH4 = ? moles CO2?

3. Cu + 2AgNO3 2Ag + Cu(NO3)2

4 moles of AgNO3 = ? moles Ag?

4. 2KI + Pb(NO3)2 PbI2 + 2KNO3

43 moles of KI = ? moles KNO3?


3. 2-Step Conversions

OBJECTIVE: Grams Moles Mole

Ratio


2H2 + O2 2H2O

You have 64 grams of O2




2H2 + O2 2H2O

You have 64 grams of O2



1. Balance 2. Grams -> Moles 3. Mole Ratio

4. 3-Step Conversions & Alternate Routes

OBJECTIVE:

Add more routes to Stoichiometry Highway


Avogadro Avenue


Avogadro Avenue

2H2 + O2 2H2O

12.04 x 1023 particles of H2

How many moles of H2O?


Liter Lane


Liter Lane

2H2 + O2 2H2O

44.8 L of H2

How many moles of H2O?

4. 3 Step Conversions and Alternate Routes

1. C5H12 C5H8 + 2H2

1.89 x 1024 molecules of C5H12. How many molecules of C5H8?

2. Br2 + 5F2 2BrF5

2.89 x 1024 molecules of Br2. How many molecules of BrF5?1.11 x 1020 molecules of F2. How many molecules of BrF5?

3. C5H12 C5H8 + 2H2

1. 366 L of C5H12. How many liters of C5H8?2. 0.0973 L of C5H12. How many liters of C5H8?3. 1.98 L of C5H12. How many liters of H2?

1. C5H12 C5H8 + 2H2


2. Br2 + 5F2 2BrF5

2.89 x 1024 molecules of Br2. How many molecules of BrF5?

1.11 x 1020 molecules of F2. How many molecules of BrF5?

3. C5H12 C5H8 + 2H2

1. 366 L of C5H12. How many liters of C5H8?2. 0.0973 L of C5H12. How many liters of C5H8?3. 1.98 L of C5H12. How many liters of H2?

4. 3 Step Conversions and Alternate Routes

1. C5H12 C5H8 + 2H2


2. Br2 + 5F 2BrF5

2.89 x 1024 molecules of Br2. How many molecules of BrF5?

1.11 x 1020 molecules of F2. How many molecules of BrF5?

5. Limiting Reactants

OBJECTIVE:

Running out of “ingredients”


8 buns + 12 pattiesWhich will run out

first?

Limiting Reactant

Excess Reactant

▪ The reactant that controls the quantity of product that can form in a chemical reaction

▪ Stuff that runs out first

▪ The reactant that is not completely used up in a chemical reaction

▪ Stuff left over


8 buns + 12 pattiesWhich is limiting?


4 franks + 12 bunsWhich is limiting?

2H2 + O2 2H2O–10 moles of H2–10 moles of O2. –How many moles of H2O?

How to Solve?Identify limiting reactant.

Limiting Reactant = Smaller Number


Fe + S Fe2S3

2Fe + 3S Fe2S3

–12 moles of Fe–12 moles of S –How many moles of Fe2S3? (Identify limiting

reactant)

WHAT IS FIRST STEP? BALANCE


NO +Cl2 NOCl–4 mol of NO–4 mol of Cl2 –How many mol of NOCl?

BALANCE FIRST!!


NO +Cl2 NOCl–100g of NO –100g of Cl2 –How many mol of NOCl?


Fe + S Fe2S3–10 moles of Fe–12 moles of S. –How many moles of Fe2S3? Identify limiting

reactant.

–150 g of Fe–120g of S. –How many grams of Fe2S3?

▪ Go to Word Document


H2 +N2 NH3

–12L of H2

–10L of N2

–How many grams of NH3?

–25g of H2, 35g of N2. How many liters of NH3?


6. Percentage Yield

OBJECTIVE:

Measuring Efficiency

6. Percentage Yield

Efficiency of a reaction =

Percentage Yield

Formula for Percentage Yield

6. Percentage Yield

Actual Yield Theoretical Yield

▪ What is actually produced.

▪ What you have been calculating so far

▪ If reaction occurs with 100% efficiency

2Al + 6HCl -> 2AlCl3 + 3H2

You calculated a theoretical yield of 8.77 grams for AlCl3. But only 5.66 grams of AlCl3 is actually produced.

What is the percentage yield?

You calculated a theoretical yield of 9.79 grams for H2. The actual yield for H2 is 4.04.

What is the percentage yield?

6. Percentage Yield

2Al + 6HCl -> 2AlCl3 + 3H2

The theoretical yield is 98.5 grams for AlCl3. This reaction has 77 percentage

yield.

What is the actual yield?

2H2O2 -> 2H2O +O2

1.How many L of O2 is produced from 250g of H2O2?

2.If reaction has 68% yield, how many L of O2 is actually produced?

2P +Cl2 -> 2PCL3

1. 500L (actual yield) of PCl3 needs to be produced.

2. The reaction as a 75% yield. How many grams of Cl2 is needed?

2P +Cl2 -> 2PCL3

1. 450g of P, 448L Cl2, ?g of PCl32. Actual Yield is 148g, what is % yield?

3. If % Yield is 48%, how much PCl3 would actually be produced

4. Suppose P is in excess, and 300g of PCl3 needed to be produced. The % Yield is 72%. How many L of Cl2 is needed?

3H2 + N2 -> 2NH3

1. 40L of H2, 15L of N2, ?g of NH3

2. Actual Yield is 17.9L of NH3, what is % Yield?

3. If reaction has % Yield of 82%, how many molecules of NH3 would be produced?

4. N2 is in excess, reaction has 62% Yield. 500L of NH3 need to produced. How many g of H2 is needed?

4. Balancing Reactions How are coefficients different from subscripts? 2H 2 + O 2 2H 2 O subscripts...

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