Practice with Molar Mass Practice with Molar Mass ProblemsProblems

::Question #1Question #1

How many moles of H2 are in 100 g of H2?

# mol H2 = 100 g H2x 1 mol H2

2.02 g H2

= 49.5 mol H2

Question #2Question #2

300 g of CuSO4 is needed in an experiment. How many moles does this represent?

# mol CuSO4 =

300 g CuSO4 x 1 mol CuSO4

159.61 g CuSO4

= 1.88 mol CuSO4

Question #3Question #3

A chemical reaction requires 23.78 moles of silver chloride. How many grams is this?

# g AgCl =

23.78 mol AgCl x 143.32 g AgCl

1 mol AgCl= 3408 g AgCl

73 g H2O

Question #4Question #4

How many molecules are in 73 grams H2O?

# H2O molecules =

x 1 mol H2O

18.02 g H2O

= 2.4 x 1024 molecules H2O

x 6.02x1023 molecules

1 mol H2O

Question #5Question #5

255 g of calcium phosphate are produced in a chemical reaction. How many moles of calcium phosphate does this represent?

# mol Ca3(PO4)2 =

255 g Ca3(PO4)2 x 1 mol Ca3(PO4)2

310.18 g Ca3(PO4)2

= 0.822 mol Ca3(PO4)2

Question #6Question #6

According to the equation 2H2 + O2 2H2O, how many grams of H2O would be produced if 7.35 mol of O2 is used up? (hint: you will need two conversion factors – 1 from the balanced equation and 1 from a molar mass)

2 mol H2O

1 mol O2

x

# g H2O=

7.35 mol O2 265 g H2O

= 18.01 g H2O

1 mol H2Ox

And you thought Chemistry was And you thought Chemistry was bad with factor-label problems!!??bad with factor-label problems!!??

Complete the following chart (#7 - #13):

Formula Molar mass

(g/mol)

Mass

(g)

Moles

(mol)

FeSO4 500

(NH4)2CO3 2

SnO2 50

Sb2O5 0.25

NaClO4 100

Mg(IO3)2 3.2

CoCl2.H2O 332

Complete the following chart (answers):

2.246332147.8CoCl2.H2O

3.21196.8374.1Mg(IO3)2

0.817100122.4NaClO4

0.2580.9323.6Sb2O5

0.33250150.7SnO2

2192.296.1(NH4)2CO3

3.29500151.9FeSO4

Moles

(mol)

Mass

(g)

Molar mass

(g/mol)

Formula

AssignmentAssignment

14. AgCl = 143.35 g/mol#g = 2 mol x 143.35 g/mol = 286.7 g (2)

15. H2 = 2.016 g/mol

#mol = 100 g x mol/2.016 g = 49.6 mol (2)

16. CuSO4 = 159.62 g/mol

#mol= 300 g x mol/159.62 g =1.879 mol (2)

17. KClO = 90.55 g/mol#mol = 250 g x mol/90.55 g = 2.76 mol (2)

Extra Review Mass-Mole-Molecules: Extra Review Mass-Mole-Molecules: Determine the number of molecules in Determine the number of molecules in 73 g of water73 g of water

73 g H2O

# H2O molecules =

x 1 mol H2O

18.02 g H2O

= 2.4 x 1024 molecules H2O

x 6.02x1023 molecules

1 mol H2O

Try this one:Try this one:

Calculate the mass in grams of iodine required to react completely with 0.50 moles of aluminum.

Al + I2 AlI32 Al + 3 I2 2 AlI3

= 190 g I2

0.50 mol Al x 3 mol I2 2 mol Al

x 253.80 g I2

1 mol I2

0.50 g Al

Try this one:Try this one:

Calculate the mass in grams of iodine required to react completely with 0.50 g of aluminum.

Al + I2 AlI32 Al + 3 I2 2 AlI3

= 7.1 g I2

x 3 mol I2 2 mol Al

x 253.80 g I2

1 mol I2

x 1 mol Al

26.98 g Al