CHM 1033 Class Assignment #4                                       Name _________________________

 

Modules 4 and 5

 

1.  Calculate the formula weight (molecular weight) of

a.  C2H6                                                  b.  Mg(NO3)2

     30 g/mole                                                148.3 g/mole

 

 

2.  How many moles are in 4.25 g of C2H6?

 

          4.25 g C2H6 x (1 mole/30 g)  =  0.142 moles

 

3.  How many grams of Mg(NO3)2 in 0.0250 moles of Mg(NO3)2?

 

          0.0250 moles Mg(NO3)2 x (143.8 g/1mole)  =  3.60 g  Mg(NO3)2

 

4. Balance the following chemical equations.

 

a.      C4H10O    +   6  O2   ®  4 CO2    +  5 H2O

 

b.      3 Mg      +     N2     ®       Mg3N2

 

5.  Consider the following balanced equation:  C5H12  +  8 O2  ®  5 CO2  +  6 H2O

a.  How many moles of O2 are needed to react with 0.725 moles of C5H12?

 

          0.725 moles C5H12 x (8 moles O2 / 1 mole C5H12)  =  5.8 moles O2

 

b.  If excess C5H12 reacts with 50.0 g O2, how many moles of CO2 are formed?

 

          50.0 g O2 x (1 mole O2 / 32.0 g O2) x (5 moles CO2 / 8 moles O2)  =  0.977 moles CO2

 

c.  If 100 g of H2O are produced, how many grams of O2 reacted?

 

          100 g of H2O x (1 mole H2O / 18.0 g H2O) x (8 moles O2 / 6 mole H2O) x (32.0 g O2 / 1 mole O2)  = 237 g O2