STOICHIOMETRY - ANSWERS
for each problem be sure to mark what type of problem it is (grams to grams, moles to moles, liters to moles, etc.)

Reaction for # 7, 8 and 9:   4Al  +  3O2  --->  2Al2O3  

These 3 are all mole to mole stoich problems

7.  How many moles of aluminum are required to form 3.7 moles of aluminum oxide?   7.4 moles

8.  How many moles of oxygen are required to react with 14.8 moles of aluminum?   11.1 moles

9.  How many moles of aluminum oxide form with the reaction of 0.78 moles of oxygen?  0.52 moles

 

Reaction for # 10 and 11:   2KClO3  --->  2KCl  + 3O2

10.  How many molecules of oxygen are produced by the decomposition of 6.54 grams of  KClO3 ? 
        This is a grams to number of particles problem,   4.82 x 1023 molecules of oxygen

11.  You have 24.8 moles of KClO3.  How many liters of oxygen are released upon total decomposition?
           This is a moles to liters problem,  833.3 Liters of oxygen

 
Reaction for # 12 (assume all are gases, at STP):   2SO2  +  O2 --->  2SO3

12.  How many liters of oxygen are needed to produce 19.8 liters of sulfur trioxide?
      This is a liters to liters problem,  9.9 liters of oxygen

 
Reaction for # 14 (all are gases, at STP):   CS2  +  3O2 --->  CO2 + 2SO2

14.  152.0 grams of carbon sulfide will produce how many grams of carbon dioxide?
       This is a grams to grams problem,  88 grams of carbon dioxide

 
Reaction for # 15 (all are gases, at STP):  2C2H2  +  5O2 --->  4CO2 + 2H2O

15. How many moles of water are produced when 2240 Liters of acetylene are combusted?
     This is a liters to moles problem, 100 moles of water

 
Reaction for # 16:  Sn(S)  + 2HF (G)  +  5O2 --->  SnF2 (S) + H2(G)

16. How many Liters of HF are needed to produce 9.4 liters of hydrogen gas at STP?
      This is a liters to liters problem,  18.8 liters of hydrogen

 
Reaction for # 17:  4P + 5O2 ---> 2P2O5

17. 3.76 moles of phosphorous can produce how many moles of diphosphorous pentoxide?
      This is a moles to moles problem,  1.88 moles of diphosphorous pentoxide

 
Reaction for # 18:  Li3N + 3H2O  ---> NH3 + 3LiOH

18. What is the mole ratio for this equation?
       This was super deluxe easy:  1:3:1:3

 
Reaction for # 19:  4K + O2  ---> 2K2O

19. If you have 9.03 x 1023  molecules of oxygen, 
      how many formula units of potassium oxide can form?
     This is a number of particles to number of particles problem, 1.81 x 1024  formula units of K2O

 
Reaction for # 20 (assume all are gases, at STP):  CO + 2H2  ---> CH3OH

20. Explain why the following set up is WRONG to figure out how many grams of methanol can be
     produced from 125.0 grams of hydrogen in this reaction.

CH3OH
H2		 1
2		 _X_
125.0

A.  the mole ratio is wrong
B.  hydrogen should be on top, methanol should be on the bottom
C.  there are no units next to the 125.0
D.  125.0 is in grams, and only moles can be used in the mole ratio

 
Reaction for # 21 (assume all are gases, at STP):  CH4 + O2  ---> CO2 + H2O

21. Explain why the following set up is WRONG to determine how many moles of oxygen are
     required to form into 1.5 moles of water.

O2
H2O		 1
1		 _X_
1.5

A.  must convert to grams or liters before you can use this format
B.  the reaction is not balanced, therefore the mole ratio is wrong
C.  the "X" goes with the water rather than the oxygen
D.  because oxygen contains 2 atoms and water molecules three, and this fact is
     not being addressed by the math in the setup