 Objective:
 Today I will be able to:



Demonstrate that stoichiometric ratios apply to balanced equations by
completing the silver nitrate lab.
Calculate percent composition of an element in a compound
Determine the percent composition of water in epsom salt by
completing a lab
 Evaluation/Assessment:
 Informal Assessment – Monitoring group interactions as they
complete the lab and the practice worksheets
 Formal Assessment – Analyzing students responses to the lab
calculations and the exit ticket
 Common Core Connection
 Value Evidence
 Make sense of problem and persevere in solving them
 Reason abstractly and quantitatively
 Attend to precision
 Use appropriate tools strategically
 Model with mathematics
Lesson Sequence
 Evaluate: Warm – Up
 Elaborate: Silver Nitrate Lab Calculations
 Explain: Percent Composition
 Engage and Explore: Epsom Salt Lab
 Evaluate: Exit Ticket
Warm - Up
 What is the difference between an empirical formula
and a molecular formula?
 Give an example
Objective
 Today I will be able to:
 Demonstrate that stoichiometric ratios apply to
balanced equations by completing the silver nitrate lab.
 Calculate percent composition of an element in a
compound
 Determine the percent composition of water in epsom
salt by completing a lab
Homework
 Study for Stoichiometry Exam


Tuesday, March 5 – B-Day
Wednesday, March 6 – A-Day
 Mole Project Due


Thursday, March 7-B-Day
Friday, March 8 – A- Day
 Finish Lab
Agenda
 Warm-Up
 Exam Study Guide
 Review HW
 Finish Silver Nitrate Lab
 Percent Composition Notes
 Percent Composition Lab
 Exit Ticket
Problems will be reviewed as a class
Silver Nitrate Lab Day 3
 Get Mass of Silver and Copper Wire
 Record in Data Table
 Perform Calculations
Silver Nitrate Lab Data Table
Group 4B Group
Members
1
2
3
4
5
6
4A Group
Members
Mass of
Copper
Wire
Before
Reaction
Mass of
Silver
Nitrate
Mass
of
Silver
Mass of
Copper
Wire
After
Reaction
What is Percent Composition?
 Percent Composition – is the mass of each
element in a compound compared to the entire
mass of the compound x 100
Percent Composition
 Example
 What is the % composition of oxygen and hydrogen in
water?
 Water = H2O = 18 g/mol
2 g H2
18 g H2O
16 g O
18 g H2O
x 100 =
11.1 % Hydrogen
x 100 =
88.9 % Oxygen
Percent Composition
 Find the % composition of a compound that contains
2.30 g sodium, 1.60 g oxygen, and .100 g hydrogen in a
4.00 g sample of the compound?
2.30 g Na
4.00 g
.100 g H
4.00 g
x 100 = 57.5 %
x 100 =
2.50 %
1.60 g O
x 100 =
4.00 g
40.0 %
Percent Composition
 A sample of an unknown compound with a mass
of .562 g has the following % composition: 13.0%
carbon, 2.20% hydrogen, and 84.8% fluorine.
When this compound is decomposed into its
elements, what mass of each element would be
recovered?
Percent Composition
13.0% C
100
2.20 % H
100
84.8 % F
100
x .562 g =
.0731 g C
x .562 g =
.0124 g H
x .562 g =
.477 g F
Epsom Salt Lab Safety
 Goggles, aprons, closed toe shoes are required to
participate
 Long hair must be tied back
 Make sure gas is turned off completely when finished
using the Bunsen burner
 Crucibles will be HOT. Do not touch. Wait 5 minutes
before taking the final mass of the crucible
Epsom Salt Lab Directions
 Today you will be working in pairs
 Once you get the lab set up, the water must evaporate
from the Epsom salt for 15 minutes
 While you wait, work on the percent composition
practice problems
 When your reaction is complete let the crucible cool
down for 5 minutes before taking the mass. It will be
HOT!
 Leave the lab area as it was when you entered.
Complete the percent composition practice after you
finish your lab. Selected problems will be reviewed as a
class.
Exit Ticket
 Using your study guide for the stoichiometry exam,
write 5 questions (and the answers) that Ms. Ose could
use on the exam next week. Write questions from all
the topics listed.