Stoichiometry: Mole Ratios
OCTOBER 14 & 15 2013
MS. BOON CHEMISTRY
Objective:
 Think Box
•I can create mole
 A cookie recipe requires 1 cup of
ratios from a
balanced chemical
equation and
perform mole to
mole conversions.
•Agenda:
•Catalyst
•One-Step
Stoichiometry Quiz
•Notes and Practice:
Mole Ratios
•Game: Reactants,
Products, and
Leftovers
sugar, 2 cups of flour, 1 stick of
butter and 3 eggs.
 How much of each ingredient do
you need in order to double the
recipe? Explain your answer.
Mini Review: What is stoichiometry?

Stoichiometry is
the study of the
relationships
between
quantities of
substances in
chemical
reactions.
Where are we going with this?

Next week you will do a lab where you will be asked to answer
questions like the one below:
 When aluminum foil is dipped in copper (II) chloride a
displacement reaction takes place:
2 Al + 3 CuCl2→ 3 Cu + 2 AlCl3
 If you dip a 10 g piece of aluminum foil into 20 mL of 0.1 M
cupper chloride, how many grams of copper metal will
form?
 To solve this problem, we need to learn how to use a mole
ratio.
Think, Pair, Share: Cookie Recipe Ratios.
 A "ratio" is just a comparison between two different





things. Look at the cookie recipe in the think box
above. List the following ratios as fractions in the
space below:
(a) sugar to flour
(b) flour to butter
(c) eggs to butter
(d) eggs to sugar
(e) butter to flour
What is a mole ratio?
• Mole ratios are used to compare the amounts of reactants and
products in a balanced chemical reaction equation.
• The coefficients represent the number of moles.
• Mole ratios are conversion factors in stoichiometry
problems.
2 Mg + O2 
2 MgO
1. What is the ratio of moles Mg atoms to moles O2
molecules?
Write this ratio as a fraction: 2 mol Mg
1 mol O2
White Board Practice #1
CH4 + 2 O2 → CO2 + 2 H2O
1 mol CH4
2 mol O2
1. What is the ratio of moles CH4 to moles O2?
2. What is the ratio of moles O2 to moles CO2?
2 mol O2
1 mol CO2
3. What is the ratio of moles H2O to moles CH4?
4. What is the ratio of moles CO2 to moles H2O?
2 mol H2O
1 mol CH4
1 mol CO2
2 mol H2O
White Board Practice #2
 Do the following problem on your white board.
2 NI3  N2 + 3 I2
 What is the mole ratio of NI3 to N2?
 Vote for your answer:
1) 1 mol NI3
2 mol N2
3) 2 mol NI3
1 mol N2
2) 2 mol NI3
2 mol N2
4) 3 mol NI3
2 mol N2
More White Board Practice
 Complete the following problems in your notes.
 Give the mole ratio between the two compounds that






are in bold red.
1) 2 FeO + 1 C  2 Fe + 1 CO2
2) 2 NO + 1 O2  1 NO2
3) 1 CH4 + 4 S  1 CS2 + 2 H2S
Balance the equations and then give the ratio
between the two compounds in bold red.
4)__PCl3 +__H2O __H3PO3 +__HCl
5)___Xe + ___F2  ___XeF4
6)__Al +__HCl __AlCl3 +__H2
Mole to Mole Conversion Problems:
 In most chemistry lab problems involving
stoichiometry, you will know or be able to find out
via measurement information about one reactant or
product. Based on this information, you will be
asked to make calculations to determine the amounts
of a different reactant or product. Mole to mole
conversions are at the heart of this idea.
Example: You react copper wire with silver nitrate. How much silver nitrate is
needed to form 5 g of silver metal as the product?
Mole to Mole Conversions: Example 1
2 Mg +
O2 
2 MgO
 How many moles of MgO can be made from 12 moles




of Mg?
Given: 12 mol Mg
Unknown: mol MgO
Conversion Factor: 2 mol MgO/ 2 mol Mg
Setup & solve:
12 mol Mg
X
2 mol MgO
2 mol Mg
=
12 mol MgO
Mole to Mole Conversions: Example 2
2 Mg +
O2 
2 MgO
 How many moles of Mg are required to produce 8




moles MgO?
Given: 8 mol MgO
Unknown: mol Mg
Conversion Factor: 2 mol Mg/ 2 mol MgO
Setup & solve:
8 mol MgO
X
2 mol Mg
2 mol MgO
=
8 mol Mg
White Board Practice #1
CH4 + 2 O2 → CO2 + 2 H2O
 How many moles of CH4 are needed to form 30 moles of




H2O?
Given:
Unknown:
Conversion Factor:
Setup & Solve:
30 mol H2O
X
1 mol CH4
2 mol H2O
=
15 mol CH4
White Board Practice #2
 Do the following problem in your notes.
2 NI3  N2 + 3 I2
 How many moles NI3 are required to produce 10 moles
N2?
 Vote for your answer:
1) 10 mol NI3
3) 5 mol NI3
2) 20 mol NI3
4) 40 mol NI3
Mole to Mole Conversion Practice
 Complete the worksheet problems on your notes.
 Work quietly with the people around you.
 Show all your work.
 Tonight’s HW: Read p. 302 – 305; Do practice
problems p. 304 #1 & 2, p. 311 #1, 4(a), 6.
Game: Reactants, Products, Left Overs
 Work with a partner.
 Show work on your white board.
 The purpose of the game is to determine the
amounts of reactants, products, or left overs based
on the given information.
 http://phet.colorado.edu/en/simulation/reactants-
products-and-leftovers
Exit Slip
2 KClO3 (s) → 2 KCl (s) + 3 O2 (g)
What is the mole ratio of KCl to O2?
2. What is the mole ratio of KCl to KClO3?
3. How many moles O2 will be produced from 4 moles
KClO3?
4. How many moles KClO3 are required to produce 32
moles KCl?
1.