Unit 6: Stoichiometry How do manufacturers know how to make enough of their desired product? - PowerPoint Presentation

Slide1

Unit 6: Stoichiometry

How do manufacturers know how to make enough of their desired product?Slide2

Chocolate Chip Cookies

Cookie Recipe

1.5 c sugar

1 c. butter

3 eggs

2.25 c. flour 2 c. chocolate chips makes 25 cookies

Using the following recipe, complete the questions.

If you have 6 c. of sugar, how many eggs will you need to use all of it?

If you have 8 c. flour, how many cookies (rounded to the nearest cookie) can you make?Slide3

Proportional Relationships

Stoichiometryis the measurement and calculation of the amounts of reactants and products in a chemical reaction

(tells a chemist how much of an element or reactant to use, how much product you can expect and specific amounts of substances)

Balanced chemical equations represent the relationship between the number of moles of reactants and the number of moles of products.

2

H

2

+ O

2

 2

H

2

OSlide4

Balanced Equation: 2 H2

+ O2  2 H

2

O

moles

2 H2 1 O2 2 H2O grams 4 g 32 g 36 gHow many moles of O2 would you need to react if you had 4 moles of H2? ______How many grams of H

2 would you need if you had 64 g of O2? _________

How many grams of water would you be able to make with 8 g of H

2

? _______

How many grams of O

2

would be used if you had only 2 g of H

2

? _______Slide5

Based on Mole RatiosA conversion factor derived from the coefficients of a balanced equation

2 H

2

+ O

2

 2 H

2 O

What is the molar ratio between

H

2

and

O

2

?

What is the molar ratio between

H

2 and H2 O?

What is the molar ratio between H2 O and O2?

2 to 2

2 to 1

2 to 1Slide6

Example: 2K (s) + Br2 → 2KBr (s)

2 mol

K

2

mol K 1 mol Br2 1 mol Br2

2 mol

KBr

2

mol

KBr

Balance the equation and write all possible mole ratios:

Al + CuSO

4

→ Al2(SO4

)3 + Cu In your notes, write down the molar relationships represented in the above equation.Slide7

What you derive from this chemical equation.

4Fe(s)

+

3O

2

(g) → 2Fe2O3 (s)Iron + oxygen → iron (III) oxide4 atoms Fe + 3 molecules O2 → 2 formula units Fe2O

3

4

mol

Fe +

3

mol

O

2

→ 2 mol Fe2O3223.4 g Fe + 96.00 g O2

→ 319.4 g Fe2O3 319.4 g reactants → 319.4 g products4Fe(s) + 3O2(g) → 2Fe2O3 (s)Slide8

When doing stoichiometry problems…

Write the balanced equation.

Determine what starting value you are given and what

unit

your final answer should be in.

Set up the correct calculation.Slide9

Stoichiometry Road MapSlide10

How many moles of copper sulfate will react with 5.00 moles of aluminum?Write balanced equation

:2. CalculationSlide11

1. Iron reacts with carbon dioxide to form iron (III) oxide and carbon monoxide. How many moles of carbon dioxide are needed to produce 2.2 moles of iron (III) oxide?Balanced equation:

  Calculation:Slide12

How many moles of carbon monoxide will also be produced?

Balanced equation:  Calculation:Slide13

When chlorine gas reacts with potassium iodide a single replacement reaction occurs. How many moles of potassium iodide will be needed to react with 2.45 moles of chlorine?

Balanced equation:  Calculation:Slide14

How many moles of iodine gas will be produced?Balanced equation:

 Calculation:Slide15

Sodium carbonate reacts with hydrochloric acid to form sodium chloride, water, and carbon dioxide gas. How many moles of sodium chloride will form from 0.65 moles of sodium carbonate?

Balanced equation: Calculation:Slide16

Stoichiometry Road MapSlide17

How many grams of ferric oxide will be produced when 0.85 moles of iron reacts with oxygen in the air?

Balanced equation:

Calculation:Slide18

How many grams of aluminum will be needed to produce 2.94 moles of aluminum chloride if the aluminum reacts with an excess of hydrochloric acid?

Balanced equation:

Calculation:Slide19

How many moles of zinc sulfate are produces when 4.55 g of zinc reacts with an excess of sulfuric acid?

Balanced equation:Calculation:Slide20

How many moles of phosphorus must be burned to produce 6.05 g of diphosphorus pentoxide?

Balanced equation:

Calculation:Slide21

Lithium nitride reacts with water to form ammonia, NH3, and lithium hydroxide. What mass of water is needed to react with 98.7 g of lithium nitride?

Balanced equation:

Calculation:Slide22

How many grams of carbon dioxide are produced when 3.785 g of methane are burned?

Balanced equation:

Calculation:Slide23

How many grams of silver nitrate are needed to react with 2.00 g of barium bromide in the double replacement reaction?

Balanced equation:

Calculation:Slide24

Percent Yield Slide25

Percent YieldStoichiometric

calculations are based on ideal reactions.

Many

reactions do not go to completion and not as much product is produced as expected.

We

can express this amount as a percentage of what we expected to get out of a particular reaction.Slide26

Percent Yield

calculated on paper

measured in labSlide27

1. Calculate the percent yield for the reaction CO2 + H

2O  H2CO

3

when 534 g of carbon dioxide react with an excess of water to produce 645 g of carbonic acid.

Actual yield = 645 g H2CO3

Theoretical yield = ? – how much should be produced?g CO2  mol CO2

 mol H2CO3



g H

2

CO

3Slide28

2. What is the % yield for the reaction Cl2 + 2KBr

 2KCl + Br2in which 214 g of chlorine react with an excess of potassium bromide to produce 412 g of bromine?Slide29

Limiting reactantsSlide30

Limiting ReactantsAvailable Ingredients

4 slices of bread1 jar of peanut butter1 jar of jelly

Limiting Reactant

bread

Excess Reactants

peanut butter and jellySlide31

Limiting Reactant

Most of the time in chemistry we have more of one reactant than we need to completely use up the other reactant.That reactant is said to be in excess

(there is too much).

The other reactant limits how much product we get. Once it runs out, the reaction stops. This is called the

limiting reactant.Slide32

Limiting Reactants

Limiting Reactantfirst reactant used up in a reaction

determines the amount of product (limits reaction)

Excess Reactant

added to ensure that the other reactant is completely used up

cheaper & easier to recycleSlide33

1. If 4.7 moles of carbon reacts with 5.5 moles of oxygen to produce carbon monoxide, which is the limiting reactant?

2 C + O2



2 CO

Choose either reactant and calculate mol to mol for the other reactant: mol C  mol O2

4.7 mol C x

1_mol_O2

=

1

2

mol

C

The limiting reactant is _______________.Slide34

2. What is the limiting reactant when 6.75 g of sodium reacts with 4.8 g of chlorine to produce sodium chloride?

Limiting reactant is _________________.Slide35

Photosynthesis equation: 6CO

2 + 6H2

O → C

6

H

12O6 + 6O23. If a plant has 2.00g of CO2 and 2.00g of water at hand which is the limiting reactant?Slide36

4. What is the plants theoretical yield of glucose under these conditions? How much of each product can you produce if the reaction is 100% efficient? How much product can you produce if the reaction is only 87.6% efficient?Slide37

5. If the plant actually makes 1.11g of glucose what is its % yield of glucose?Slide38

6. How much of the excess reactant will be left unreacted?