Stoichiometry ICS III Week 6

Baking Recipe Ingredients Ingredients –1 cup unsalted butter (B) –1 cup sugar (S) –1 cup brown sugar (Bs) –2 large eggs (E) –1 teaspoon pure vanilla extract (V) –3 cups flour (F) –1 teaspoon salt (Na) –2 cups chocolate chips (Cc) –Bake for degrees O F Makes up to 50 cookies (Co) Makes up to 50 cookies (Co)

Chemical Reactions Chemical reaction Chemical reaction –When bonds are broken and rearranged to form a new substance –Reactant(s) A substance present at the start of a reaction A substance present at the start of a reaction You can have 1 reactant or 1,000 reactants You can have 1 reactant or 1,000 reactants –Product(s) Substance produced in a chemical reaction Substance produced in a chemical reaction You can have 1 product or 1,000 products You can have 1 product or 1,000 products

Chemical Equation Chemical Equation –A representation of a chemical reaction The formulas of the reactants (on the left) are connected by an arrow with the formulas of the product (on the right). The formulas of the reactants (on the left) are connected by an arrow with the formulas of the product (on the right). REACTANT 1 + REACTANT 2 PRODUCT 1 + PRODUCT 2 Yields

Baking Recipe Ingredients Ingredients –1 cup unsalted butter (B) –1 cup sugar (S) –1 cup brown sugar (Bs) –2 large eggs (E) –1 teaspoon pure vanilla extract (V) –3 cups flour (F) –1 teaspoon salt (Na) –2 cups chocolate chips (Cc) –Bake for degrees O F Makes up to 50 cookies (Co) Makes up to 50 cookies (Co) Letters are symbols that indicate a specific compound. B = butter Reactants Product

Chemical Reaction for Baking Chocolate Chip Cookies –1 cup unsalted butter (B) –1 cup sugar (S) –1 cup brown sugar (Bs) –2 large eggs (E) –1 teaspoon pure vanilla extract (V) –3 cups flour (F) –1 teaspoon salt (Na) –2 cups chocolate chips (Cc) –Bake for degrees O F Makes up to 50 cookies (Co) Makes up to 50 cookies (Co) B + S + Bs + E + V + F + Na + Cc  Co B + S + Bs + E + V + F + Na + Cc  Co B + S + Bs + 2E + V + 3F + Na + 2Cc  50Co B + S + Bs + 2E + V + 3F + Na + 2Cc  50Co When ever you don’t put a number, it automatically indicates only 1 compound Coefficient Coefficient –A number that represents how many compounds are present in a reaction

Making a Bicycle +++ Frame + 2 wheels + handlebar + 2 pedals bicycle F + 2W + H + 2P ---  FW 2 HP 2 Reactants Product

Conservation of Mass In a chemical reaction mass and atoms are conserved in every chemical reaction. In a chemical reaction mass and atoms are conserved in every chemical reaction. –What ever is on the left must equal what is on the right. – __ grams + 40 g = 77 g – 37 grams

Stoichiometry Stoichiometry Stoichiometry –Calculation of quantities in chemical reactions –Allows chemists to tally the amounts of reactants and products using ratios of moles or representative particles. Mole Ratio Mole Ratio –Conversion factor derived from the coefficients of balanced chemical equations interpreted in terms of moles

How Stoichiometry Works If you react 20 grams of sodium hydroxide with an excess of hydrochloric acid, how much water would result? If you react 20 grams of sodium hydroxide with an excess of hydrochloric acid, how much water would result? –You always want to work with moles! –Go through the steps What is given What is given What are you looking for? What are you looking for? How do we get there? How do we get there?

How Stoichiometry Works What is given? –2–2–2–20 grams NaOH What are we looking for? –G–G–G–Grams water (H2O) How do we get there?? –C–C–C–Convert to moles –M–M–M–Mole ratio –C–C–C–Convert to grams

Mole Ratio Moles of wanted compound Moles of given compound The coefficient goes in front The coefficient goes in front

How 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 Fe 2 O 3 are required to completely react with 84 grams of CO?In this reaction, how many grams of Fe 2 O 3 are required to completely react with 84 grams of CO? How Stoichiometry Works What is given Convert from grams to moles MOLE RATIO Convert from moles to grams What is wanted

aG bW (given quantity) (wanted quantity)

aG bW (given quantity) (wanted quantity)

aG bW (given quantity) (wanted quantity)

CH 4 + 2O 2 CO 2 + 2H 2 O The Equation above shows the reaction of methane (CH 4 ) burning in the presence of oxygen. If 32 grams of methane react completely with oxygen, how many grams of carbon dioxide (CO 2 ) will be formed? a) 32 g b) 44 g c) 56 g d) 88g