1. Unit: Stoichiometry Mass-mass calculations using the mole ratio
Day 2 - Notes
Unit: Stoichiometry
Mass-mass calculations using the mole ratio
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2. After today you will be able to…
Calculate the number of grams produced or reacted of a substance given a chemical equation

3. There are three steps needed for these calculations:
Convert gramsmoles (Using the MM of the known.)
Convert moles of knownmoles of unknown using the mole ratio (We learned this yesterday!)
Convert moles of unknown grams (Using MM of the unknown.)

4. Mass-Mole-Mole Calculations
Example: How many grams of H2O are produced if 2.2 mol of NH3 are combined with excess oxygen?
4 NH O2  6 H2O NO
59 g H2O

5. Mass-Mole-Mole Calculations
4 NH O2  6 H2O NO
Example: How many grams of O2 are required to produce 0.3 mol of H2O?

6. There are three steps needed for these calculations:

7. Mass-Mass Calculations
Example: What mass of silver chloride will react with 15.0g of aluminum?
__Al 1
__ AgCl 3
__ Ag 3 +
__ AlCl3 1  +
1Ag = )
K: 15.0 gAl
1Cl =35.45(1)
U: ? gAgCl
143.32g
15.0 gAl 1
1 mol Al
26.98 gAl
3 mol AgCl
1 mol Al
gAgCl
1 mol AgCl x x x
239g AgCl =

8. Mass-Mass Calculations
Example: What mass of oxygen gas would be produced from the decomposition of 37.2g of lithium chlorate? 2
__Li(ClO3)
__ LiCl 2 +
__ O2 3 
1Li =6.94(1)
K: 37.2 gLi(ClO3)
1Cl =35.45(1)
3O =16.00(3)
U: ? gO2
90.39g
37.2 gLi(ClO3) 1
1 mol Li(ClO3)
90.39 gLi(ClO3)
3 mol O2
2 mol Li(ClO3)
32.00 gO2
1 mol O2 x x x
19.8 gO2 =

9. SUMMARY OF IMPORTANT POINTS:
You are calculating the mass for TWO different substances!
Molar mass (MM) is ALWAYS equal to ONE mole!
The ONLY time the number of moles is different than ONE (1) is when you are doing the MOLE RATIO STEP!

10. Complete WS 2 for HOMEWORK!
Questions?
Complete WS 2 for HOMEWORK!
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