Unit: StoichiometryMass-mass calculations using the mole ratio

Day 2 - Notes

Day 2 - Notes

After today you will be able to…

• Calculate the number of grams produced or reacted of a substance given a chemical equation

There are three steps needed for these calculations:1.Convert gramsmoles (Using the MM of the known.)2.Convert moles of knownmoles of unknown using the mole ratio (We learned this yesterday!)•Convert moles of unknown grams (Using MM of the unknown.)

Mass-Mass CalculationsExample: What mass of silver chloride will react with 15.0g of aluminum?

__Al + __ AgCl __ Ag + __ AlCl31 3 3 1

K: 15.0 gAlU: ? gAgCl

15.0 gAl1

x3 mol AgCl1 mol Al

=239g AgCl

1 mol Al26.98 gAl

x x 143.32 gAgCl

1 mol AgCl

1Ag =107.871)1Cl =35.45(1)

143.32g

AlAgCl

111

1133

3 3Review!

Mass-Mass CalculationsExample: What mass of oxygen gas would be produced from the decomposition of 37.2g of lithium chlorate?

__Li(ClO3) __ LiCl + __ O22 2 3

K: 37.2 gLi(ClO3)U: ? gO2

37.2 gLi(ClO3)1

x 3 mol O2

2 mol Li(ClO3)

=19.8 gO2

1 mol Li(ClO3) 90.39 gLi(ClO3)

x x 32.00 gO2

1 mol O2

1Li =6.94(1)1Cl =35.45(1)3O =16.00(3)

90.39g

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!

Questions?

Complete WS 2 for HOMEWORK!