DO NOW
Take out your DEAR book and read
silently for 15 minutes.
Explore Problem
How many moles of sucrose are in a tablespoon
of sugar that contains 2.85g? (The molar mass of
sucrose is 342.0g/mol).
Solution
Given: mass of sucrose
Unknown: moles of sucrose
Equation: stoichiometry conversion
Substitute: so that units cancel
Solution
2.85g sucrose X 1 mol sucrose
___________ = 8.33E-3 mol
342.0g sucrose
Example problem
How many grams are in 0.0626mol of NaHCO3,
the main component of baking soda?
Solution
Step 1: Determine formula mass of NaHCO3
Step 2: Determine molecular mass of NaHCO3
Step 3: Stoichiometry conversion
Solution
Formula mass = Na + H + C + 3 O
= 23amu + 1amu + 12amu + (3X16amu)
=84amu
Molar mass = 84.0 g/mol
Stoich conversion:
0.0626 mol NaHCO3 X 84 g
___________ = 5.26 g
1mol NaHCO3
Example problem
How many molecules of aspirin are in a tablet
weighing 500mg? (formula: C9H8O4)
Solution
Molar mass: 180.2g
0.500g X 1mol aspirin
_________ = 2.77E-3 mol aspirin
180.2g
2.77E-3 mol X 6.022E23 molecules
________________
1 mol
= 1.67E21 molecules
Your Turn!
• (See Worksheet)
DO NOW
Household bleach is prepared by mixing sodium
hydroxide with chlorine in the following
reaction:
2 NaOH + Cl2  NaOCl + NaCl + H2O
How many grams of NaOH are needed to react
with 25.0g of Cl2?
Solution
Stoich flow chart:
-given grams, want grams
Grams Cl2 -> Moles Cl2 -> Moles NaOH -> Grams NaOH
Solution
25g Cl2 X 1 mol Cl2
________
70.9g Cl2
= 0.353 mol Cl2
0.353 mol Cl2 X 2 mol NaOH X 40g NaOH
__________ _________ = 28.2g NaOH
1 mol Cl2
1mol NaOH
**shortcut: set up all steps in one conversion
Example Problem
How many grams of acetic anhydride are
needed to react with 4.50g of salicylic acid? How
many grams of aspirin will be produced?
C7H6O3 + C4H6O3 -> C9H8O4 + CH3COOH
Salicylic
acetic
aspirin
acetic
Acid
anhydride
acid
Solution
4.5g SA X 1 mol SA X 1 mol SAX 102.1g AA
_______
______
________ = 3.33g AA
138.1 g SA 1 mol AA
1 mol AA
(Same process for A)
Big Paper Practice
Do Now
• Questions before quiz?
Quiz
Percent Yield
https://www.youtube.com/watch?v=pFmCncwOW8
Percent Yield
Formula:
Percent yield = Actual Yield
__________
Theoretical Yield
X 100
Your turn!
• Jigsaw Worksheet
DO NOW
• Read pages 99 – 103 silently at your desks.
Write down one question you have on the
sticky note at your desk.
LR/IE
• Limiting reactant- reactant you NEED but
DON’T have in order to proceed
• In excess- reactant that there is MORE of than
needed for the reaction to proceed
• Calculate in terms of MOLES first
Sample Problem
• Worked Example 3.10 (written on board)
Your turn!
• Boardwork Relay Race worksheet