Irrelevant Information to Take Your Mind Off of Stoichiometry The first person to use the word “stoichiometry” was Nicephorus I, the ecumenical Patriarch of Constantinople in the early 9th century. However, the term as he used it refers to the number of lines of text in the New Testament. This suggests that the term “stoichiometry” has been annoying people for over a millennium. Image: Classical Numismatic

Chapter 11: Stoichiometry• Be able to complete molarity equations/problems• Know mole ratio’s• Use mole ratio’s to complete stoichiometry problems• Complete:• Mol/mol• mol/mass• Mass/mass

• Identify limiting and excess reactants• Calculate the % yield

Molarity, Mole Ratio’s, and Mol to Mol Stoichiometry

Molarity:

• describes how much solute there is per solution.

Molarity (M) = Moles of solute Liters of solution

*aqueous solutions are solutes dissolved in water.

Molarity:• We have a solution that is made of 45.6 grams of sodium

chloride dissolved in 378 mL of water. What is the solutions molarity? (Answer=2.08 M)

Step 1: Change grams to moles

Step 2: Change volume to liters

Step 3: Divide the number of moles by the volume of the solution

45.6g NaCl

58g NaCl

1 mol NaCl= 0.786 mol NaCl

378 mL1000 mL

1 L= 0.378 L

0.786 mols NaCl 0.378 L = 2.08 M

Molarity Practice: Write these down in your notes• A solution is made by dissolving 3.21 moles of sulfuric acid

into 506 mL of water. What is the molarity of the solution?

• If a solution is made by adding 3230 grams of lithium carbonate to 2.2 liters of water, what will the molarity of the solution be?

• 121.4 grams of potassium oxide are dissolved in 34.5 mL of water, what is the solutions molarity?

Molarity Practice Problem #1:• A solution is made by dissolving 3.21 moles of sulfuric acid

into 506 mL of water. What is the molarity of the solution?

Molarity Practice Problem #2:• If a solution is made by adding 3230 grams of lithium

carbonate to 2.2 liters of water, what will the molarity of the solution be?

Molarity Practice Problem #3:• 121.4 grams of potassium oxide are dissolved in 34.5 mL of

water, what is the solutions molarity?

Stoichiometry:• The quantitative relationships between the amounts of

reactants used and the amounts of products formed by a chemical reaction.

• Which is just a fancy way of saying:• “the method you use to figure out how much of a chemical you

can make, or how much you need, during a reaction.” • What is Stoichiometry?

Stoichiometry:• 1. How to balance chemical equations• 2. How to convert grams to moles/moles to grams• 3. How to use mole ratios

Can you do 1 and 2?

Mole Ratios:• Ratio- a relationship between two numbers of the same kind.

2H2 + O2 2H2O

*Use the coefficients of the balanced chemical reaction to

determine the mole ratios.

Ratios:2 hydrogen for 1 oxygen2 hydrogen for 2 water

1 oxygen for 2 water

Mole Ratio’s:Calculate the mole ratio for each substance in the following reactions.

__Fe + __O2 ⇒ __Fe2O3

__C3H8 + __O2 ⇒ __CO2 + __H2O

Stoichiometry and Mole Ratios:• Knowing the mole ratios allows you to begin doing

stoichiometry:

2H2 + O2 2H2O

If we have 5 moles of hydrogen reacting, how many moles of water are formed?

5 moles H2

2 moles H2

2 moles H2O= 5 moles H2O

Mole ratio between the two compounds in the problem

The Amount Given

Stoichiometry: mols to mols

If there are 3.5 moles of potassium reacting, how many moles of hydrogen will form?

Mols to Mols Practice: Complete in your notes

__Fe + __O2 ⇒ __Fe2O3

If you only had 0.45 moles of Fe how many moles of Fe2O3 would you produce?

How many moles of O2 were used?

Mols to Mols Practice: Complete in your notes

__C3H8 + __O2 ⇒ __CO2 + __H2O

If 7.8 moles of O2 are used how much C3H8 was also used?

How many moles of CO2 were produced?

Mols to Mols Practice: Complete in your notes

__AgNO3 + __Cu ⇒ __Cu(NO3)2 + __Ag

10.2 moles Cu are used to react with AgNO3, how many moles of AgNO3 were used to react?

How many moles of Silver are produced?