_____  pts. out of 66 pts. = ______ % =                                                                            Name:

 

Advanced Chemistry: Quiz #3 (Thermodynamics)

 

1.     Given the following reactions and corresponding heats of reaction:

 

       2 NH3 + 3 N2O ® 4 N2 + 3 H2O                DH = -1010. kJ

 

       N2O + 3 H2 ®  N2H4 + H2O                      DH = -317. kJ

 

       2 NH3 + ½ O2 ® N2H4 + H2O                    DH = -143. kJ

 

       H2 + ½ O2 ®  H2O                                           DH = -286. kJ

 

 

       Calculate the heat of reaction for:  

 

       N2H4 + O2 ® N2 + 2 H2O            (14 pts.) 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.         A 40.0 g piece of metal having an initially temperature of 550.0 oC is dropped into an insulated container holding 100.0 ml of water having an initial temperature of 25.3 oC.  The final temperature of the water and the metal is 33.5 oC.  What is the specific heat of the metal?   (10 pts.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.         While on a camping trip in the Canadian Rockies, you happen to see a 258.6g nugget of gold on the ground near the campfire.  Without thinking the situation through completely, you pick up the nugget of gold, and only then realize how close the nugget was to the fire.  The nugget has a temperature 378.4 °C as you quickly drop it into the mug you are holding containing 191.0 ml of water that initially has a temperature of 15.0 °C.  For some reason you have now become more cautious and you wonder if it is now safe to put your hand in the water to retrieve the nugget.  So, remembering your chemistry, you sit down and calculate the final temperature of the water.  What is the final temperature of the water?     (10 pts.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.         Propane (C3H8) has a heat of combustion of -2220. kJ/mol.  How many liters (measured at STP) of propane are needed to melt 1.00 pound (453.6 g) of gold that is initially at room temperature? (12 pts.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.         How many liters of oxygen gas (measured at STP) are needed to support the combustion of the propane in the previous problem?  (2 pts.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.   How many grams of ethylene (C2H4) must be burned to completely vaporize 185.6 g of H2O that is initially at -75.6 oC?  (18 pts.)