CHM 2045C Module Seven Sample Exam 

 

Module Seven Part G: Hess Law of Constant Heat Summation    10 points

 

Using the following equations:

 

          S (s)        +  3/2 O2 (g)               SO3 (g)      Ho =   -395.2 kJ

 

      2 SO2 (g)     +       O2 (g)             2 SO3 (g)   ∆ Ho =    -198.2 kJ

 

calculate the   Ho for the reaction:

 

          S (s)          +       O2 (g)                     SO2 (g)

 

 

 

 

 

 

 

 

 

 

 

 

 

Given the following equations:

 

  B2O3 (s)   +  3H2O (g)         B2 H6 (g)   +  3 O2 (g)          ∆ Ho =  +2035 kJ

 

                        H2O (l)           H2O (g)                               ∆ Ho =    +44 kJ

 

  2 B (s)     +    3 H2 (g)         B2 H6 (g)                             ∆ Ho =    +36 kJ

 

     H2 (g)         + 1/2  O2 (g)        H2O (l)                                ∆ Ho =   -286 kJ

                                 

Calculate the ∆ Ho for the reaction:

 

         2 B (s)     +    3/2  O2 (g)     B2 O3 (s)      

 

 

 

 

 

 

 

Answer:  -1273 kJ