StoichiometryStoichiometry

ICS IIIICS III

Week 6Week 6

Baking RecipeBaking Recipe• IngredientsIngredients

– 1 cup unsalted butter (B)1 cup unsalted butter (B)– 1 cup sugar (S)1 cup sugar (S)– 1 cup brown sugar (Bs)1 cup brown sugar (Bs)– 2 large eggs (E)2 large eggs (E)– 1 teaspoon pure vanilla extract (V)1 teaspoon pure vanilla extract (V)– 3 cups flour (F)3 cups flour (F)– 1 teaspoon salt (Na)1 teaspoon salt (Na)– 2 cups chocolate chips (Cc)2 cups chocolate chips (Cc)– Bake for 30 minutes @ 375 degrees Bake for 30 minutes @ 375 degrees OOFF

• Makes up to 50 cookies (Co)Makes up to 50 cookies (Co)

Chemical ReactionsChemical Reactions

• Chemical reactionChemical reaction– When bonds are broken and rearranged When bonds are broken and rearranged

to form a new substanceto form a new substance– Reactant(s)Reactant(s)

•A substance present at the start of a A substance present at the start of a reactionreaction

•You can have 1 reactant or 1,000 reactantsYou can have 1 reactant or 1,000 reactants

– Product(s)Product(s)•Substance produced in a chemical reactionSubstance produced in a chemical reaction

•You can have 1 product or 1,000 productsYou can have 1 product or 1,000 products

• Chemical EquationChemical Equation– A representation of a chemical reactionA representation of a chemical reaction

•The formulas of the reactants (on the left) The formulas of the reactants (on the left) are connected by an arrow with the formulas are connected by an arrow with the formulas of the product (on the right).of the product (on the right).

REACTANT 1 + REACTANT REACTANT 1 + REACTANT 22

PRODUCT 1 + PRODUCT PRODUCT 1 + PRODUCT 22

YieldsYields

Baking RecipeBaking Recipe• IngredientsIngredients

– 1 cup unsalted butter (B)1 cup unsalted butter (B)– 1 cup sugar (S)1 cup sugar (S)– 1 cup brown sugar (Bs)1 cup brown sugar (Bs)– 2 large eggs (E)2 large eggs (E)– 1 teaspoon pure vanilla extract (V)1 teaspoon pure vanilla extract (V)– 3 cups flour (F)3 cups flour (F)– 1 teaspoon salt (Na)1 teaspoon salt (Na)– 2 cups chocolate chips (Cc)2 cups chocolate chips (Cc)– Bake for 30 minutes @ 375 degrees Bake for 30 minutes @ 375 degrees OOFF

• Makes up to 50 cookies (Co)Makes up to 50 cookies (Co)

Letters are symbols that indicate a specific compound. B = butter

React

an

ts

Product

Chemical Reaction for Baking Chemical Reaction for Baking Chocolate Chip CookiesChocolate Chip Cookies

– 1 cup unsalted butter (B)1 cup unsalted butter (B)– 1 cup sugar (S)1 cup sugar (S)– 1 cup brown sugar (Bs)1 cup brown sugar (Bs)– 2 large eggs (E)2 large eggs (E)– 1 teaspoon pure vanilla extract (V)1 teaspoon pure vanilla extract (V)– 3 cups flour (F)3 cups flour (F)– 1 teaspoon salt (Na)1 teaspoon salt (Na)– 2 cups chocolate chips (Cc)2 cups chocolate chips (Cc)– Bake for 30 minutes @ 375 degrees Bake for 30 minutes @ 375 degrees OOFF

• Makes up to 50 cookies (Co)Makes up to 50 cookies (Co)

•B + S + Bs + E + V + F + Na + Cc B + S + Bs + E + V + F + Na + Cc CoCo•B + S + Bs + 2E + V + 3F + Na + 2Cc B + S + Bs + 2E + V + 3F + Na + 2Cc 50Co50Co

When ever you don’t put a number, it When ever you don’t put a number, it automatically indicates only 1 compoundautomatically indicates only 1 compound

• CoefficientCoefficient– A number that represents how many compounds are present A number that represents how many compounds are present

in a reactionin a reaction

Making a BicycleMaking a Bicycle

+ + +

Frame + 2 wheels + handlebar + 2 pedals bicycle

F + 2W + H + 2P --- FW2HP2

Reactants

Product

Conservation of MassConservation of Mass

• In a chemical reaction mass and atoms are In a chemical reaction mass and atoms are conserved in every chemical reaction.conserved in every chemical reaction.– What ever is on the left must equal what is on What ever is on the left must equal what is on

the right.the right.

– __ grams + 40 g = 77 g__ grams + 40 g = 77 g– 37 grams 37 grams

_?_ g 40 g 59 g 18 g

HCl + NaOH NaCl + H2OHydrochloric

acidsodium

hydroxidesodium chloride water

StoichiometryStoichiometry

• StoichiometryStoichiometry– Calculation of quantities in chemical Calculation of quantities in chemical

reactionsreactions– Allows chemists to tally the amounts of Allows chemists to tally the amounts of

reactants and products using ratios of reactants and products using ratios of moles or representative particles.moles or representative particles.

• Mole RatioMole Ratio– Conversion factor derived from the Conversion factor derived from the

coefficients of balanced chemical coefficients of balanced chemical equations interpreted in terms of molesequations interpreted in terms of moles

How Stoichiometry WorksHow Stoichiometry Works

• If you react 20 grams of sodium If you react 20 grams of sodium hydroxide with an excess of hydroxide with an excess of hydrochloric acid, how much water hydrochloric acid, how much water would result?would result?– You always want to work with moles!You always want to work with moles!– Go through the stepsGo through the steps

•What is givenWhat is given

•What are you looking for?What are you looking for?

•How do we get there?How do we get there?

How Stoichiometry WorksHow Stoichiometry Works

• What is given?What is given?– 20 grams NaOH20 grams NaOH

• What are we looking for?What are we looking for?– Grams water (H2O)Grams water (H2O)

• How do we get there??How do we get there??– Convert to molesConvert to moles– Mole ratioMole ratio– Convert to gramsConvert to grams

Mole RatioMole Ratio

Moles of wanted compoundMoles of wanted compound

Moles of given compoundMoles of given compound

• The coefficient goes in frontThe coefficient goes in front

How Stoichiometry WorksHow Stoichiometry Works

What is given

Convert from grams

to moles

MOLE RATIO

Convert from moles to grams

What is wanted

•In this reaction, how many grams of FeIn this reaction, how many grams of Fe22OO33 are are required to completely react with 84 grams of required to completely react with 84 grams of CO?CO?

How Stoichiometry WorksHow Stoichiometry Works

What is given

Convert from grams

to moles

MOLE RATIO

Convert from moles to grams

What is wanted

aG bWaG bW(given quantity) (wanted quantity)

aG bWaG bW(given quantity) (wanted quantity)

aG bWaG bW(given quantity) (wanted quantity)

CHCH44 + 2O + 2O22 CO CO22 + 2H + 2H22OO

1. The Equation above shows the reaction of methane (CH4) burning in the presence of oxygen. If 32 grams of methane react completely with oxygen, how many grams of carbon dioxide (CO2) will be formed?

a)a) 32 g32 gb)b) 44 g44 gc)c) 56 g56 gd)d) 88g88g