Ch. 6 Thermochemistry Review                                                Name _________________

                                                                                                Date _______________

                                                                                                Period ________________

 

Multiple Choice – circle the best answer for the following questions.

 

  1. An amount of heat equal to 3500 J is added to a system. In addition, 1500 J of work is done by the system on the surroundings. What is the change in internal energy of the system?
    1. 1500 J
    2. 2000 J
    3. 3500 J
    4. 5000J
    5. – 5000J

 

  1. The standard enthalpy change for the reaction below is – 482 kJ. Calculate the heat released when 12.0 g of CO (g) reacts completely, according to the following chemical equation:  2 CO (g) + O2 (g) à 2 CO2 (g)
    1. 2.89 x 103 kJ
    2. 206 kJ
    3. 103 kJ
    4. 65.7 kJ
    5. – 482 kJ

 

  1. For a specific process, ∆H = - 432 J. This process is
    1. Endothermic    
    2. Exothermic
    3. Positive
    4. negative
    5. zero

 

  1. ∆E is always positive
    1. when a system absorbs heat and does work
    2. when a system gives off heat and does work
    3. when a system absorbs heat and has work done on it
    4. when a system gives off heat and has work done on it
    5. in none of the circumstances listed above.

 

  1. Under what condition(s) is the enthalpy change of a process equal to the amount of heat transferred into or out of the system? Hint: P∆V = - w

                                                               i.      Temperature is constant

                                                             ii.      Pressure is constant

                                                            iii.      Volume is constant

a.       i only

b.      ii only

c.       iii only

d.      i and ii

e.       ii and iii

 

  1. What is the specific heat of iron if 13.5 J is required to raise the temperature of a 10-g sample 3 K?
    1. 0.45 J/gK
    2. 2.22 J/gK
    3. 4.05 J/gK
    4. 45 J/gK
    5. 405 J/gK

 

  1. The specific heat of methane, CH4, is 2.20 J/gK. What is the molar heat capacity of methane?
    1. 0.137 J/gK
    2. 2.20 J/gK
    3. 7.30 J/gK
    4. 16.05 J/gK
    5. 35.31 J/gK

 

  1. Given that:

2S(s) + 3 O2(g) à 2SO3(g)                 ∆H = -790kJ

S(s) + O2(g) àSO2(g)                         ∆H = - 297 kJ

           

            What is the enthalpy of the reaction in which sulfur dioxide is oxidized to sulfur

             trioxide?

                        2SO2(s) + O2(g) à 2SO3(g)

a.       196 kJ

b.      – 196 kJ

c.       1087 kJ

d.      – 1384 kJ

e.       – 543 kJ

 

  1. For what species in the following chemical reaction is ∆Hof zero?

2Co(s) + H2(g) + 8PF3(g) à 2HCo(PF3)4 (l)

    1. Co(s)
    2. H2(g)
    3. PF3
    4. HCo(PF3)4 (l)
    5. Both Co(s) and H2(g)

 

  1. For which of the following reactions is the value of ∆Horxn equal to ∆Hof  for the product?
    1. H2(g) + ½ O2(g) à H2O (l)
    2. H2(g) + O2(g) à H2O(l)
    3. 2C(s,graphite) + 2H2(g) à C2H4(g)
    4. ½ N2(g) + O2(g) à NO2(g)
    5. All of the above.
  2. Consider the following reaction:

2H2(g) + O2(g) à 2H2O(l)        ∆H = - 572 kJ

 

    1. How much heat is evolved for the production of 1.00 mol of H2O (l)?
    2. How much heat is evolved when 4.03 g of hydrogen is reacted with excess oxygen?
    3. How much heat is evolved when 186 g of oxygen is reacted with excess hydrogen?

 

 

 

 

 

 

 

 

 

 

  1. Given the following data

P4(s) + 6Cl2(g) à 4PCl3(g)                  ∆H = - 1225.6 kJ

P4(s) + 5 O2(g) à P4O10 (s)                 ∆H = - 2967.3 kJ

PCl3(g) + Cl2 (g) à PCl5(g)                 ∆H = - 84.2 kJ

PCl3(g) + ½ O2(g) à Cl3PO (g)           ∆H = - 285.7 kJ

            Calculate the ∆H for the reaction P4O10(s) + 6 PCl5(g) à 10 Cl3PO(g)

 

 

 

 

 

 

 

 

  1. The standard enthalpy of combustion of ethane gas, C2H4(g), is – 1411.1 kJ/mol at 298 K. Given the following enthalpies of formation, calculate ∆Hof for C2H4(g).

CO2(g) =  - 393.5 kJ/mol

H2O(l) = - 285.8 kJ/mol