Tonight’s Homework

• skim ch 11.2 (373 – 377)• p 393, # 60 – 64, 67

Stoichiometry – ch 11

A cupcake analogy

5 eggs + 1 box cake mix 18 cupcakes

+

What do I need to make 36 cupcakes…

10 eggs + 2 boxes cake mix 36 cupcakes

+

How many cupcakes can I make if I have 1 dozen eggs

and 2 boxes mix?12 eggs + 2 boxes cake mix

+

+

36 cupcakes

How many cupcakes can I make if I have 1 dozen eggs

and 3 boxes mix?12 eggs + 3 boxes cake mix

+

36 cupcakes

+

+

What if I started with 300 g eggs and 90 g cake mix?

Convert to a unit that can be used to compare the two…

Chemists use MOLES!!!

Stoichiometry

• Big Idea: The amount of each reactant present determines how much product can form.

• stoichiometry: the study of quantitative relationships between the amounts of reactants used and amounts of products formed in a chemical reaction.

Stoichiometric Calculations

section 11.2

Mass Production (an analogy )

• 2-L bottles of soda• 100,000 bottles per

order• Best case scenario, how

many liters of soda should be “batched” at a time?

• 200,000 L

Thinking like a chemist…

• “Balanced Chemical Equation”

• Mole Ratio

• Conversion

The basics of stoichiometric conversions…

• Best Case Scenario = Balanced Chemical Eqn.• The mole ratio is the missing link between the best

case scenario (balanced chemical equation in moles) and reality (in grams).– DETERMINE mole ration FROM THE BALANCED EQUATION

• 3 types of conversions– mole to mole– mole to mass– mass to mass

• Use molar mass (MM) to convert between moles and mass.

For all of them, GO TO MOLES FIRST!

3 groups – 3 reactions

• http://commons.wikimedia.org/wiki/File:Potassium_water_20.theora.ogv or– https://www.youtube.com/watch?v=oqMN3y8k9So

• http://www.teachertube.com/viewVideo.php?video_id=67110 or– https://www.youtube.com/watch?v=Mx5JJWI2aaw

• http://teachertube.com/viewVideo.php?video_id=122767&title=WHOOSH______Bottle&vpkey=&album_id=– https://www.youtube.com/watch?v=x2BXuI52fOI

3 groups – 3 problems

• Determine what type of conversion– mole to mole– mole to mass– mass to mass

• Work through the problem to solve it.• Outline the steps to solve this type of

problem.• Be prepared to teach it to your classmates.

Summary – Determine given and unknown, then…

moles given to moles unknown

mole give to mass unknown

mass given to mass unknown

1. Balance chemical equation.

1. Balance chemical equation.

1. Balance chemical equation.

2. Determine and use the mole ratio to relate moles unknown to moles given.

2. Determine and use the mole ratio to relate moles unknown to moles given.

2. Convert mass given to moles given using molar mass.

3. Convert moles unknown to mass using molar mass.

3. Determine and use the mole ratio to relate moles unknown to moles given.

4. Convert moles unknown to mass unknown using molar mass.

= moles given x (moles unknown/moles known)

= moles given x (moles unknown/moles known) x (MM unknown/1mole)

= mass given x (1mole/MM) x (moles unknown/moles known) x (MM unknown/1 mole)

Groups 1 & 2

• Potassium metal reacts vigorously with water to produce potassium hydroxide and hydrogen gas. If 0.0400 moles of potassium is used, how many moles of hydrogen gas is created?

Groups 3 & 4

• Determine the mass of sodium chloride (NaCl) commonly called table salt, produced when 1.25 moles of chlorine gas (Cl2) reacts vigorously with excess sodium.

Groups 5 & 6

• Gasohol is a mixture of gasoline and ethanol. Determine the mass of CO2 produced from the combustion of 100.0 g ethanol (C2H5OH).