CH221 - 11:00                   EXAM #2-A                                   Practice


CONSTANTS   

        Avogadro:      6.022  1023 /mole 

         Energy:          1 cal = 4.184 J 

  


Select the best single answer for each question:

1.  Use the thermochemical equation

                                        2HF(g)    H2(g) + F2(g)   ,    DH = 542.2 kJ

to determine the enthalpy of formation of HF(g).                       

A) -542.2 kJ
B) -271.2 kJ   
C) -135.6 kJ
D)  135.6 kJ
E)  271.2 kJ

2. The number of ions released when 0.618 mol of copper(II) nitrate trihydrate dissolves completely in water is

  
A) 1.12 1024  
B) 1.49  1024 
C) 7.44  1023
D) 1.20  1024
E) 2.23  1024
    

3.  Which is the weakest electrolyte in water?

A) HNO3
B) H2SO4
C) NaOH
D) HCl
E) CH3COOH    
  

4.  List the spectator ions for the reaction  KI(aq) + AgNO3(aq)    KNO3(aq) + AgI(s)
         
A) K+,  I-,  Ag+,  NO3-  
B) Ag+,  I-  
C) NO3- 
D) K+,  NO3-   
E) K+
 


5.   What is the concentration of an HCl solution if 45.6mL of it neutralizes 26.3mL of 0.165M NaOH ? 

         
A) 9.52 10-2
B) 1.23 10-1 M  
C) 2.92 10-1
D) 7.16 10-2
E) 1.90 10-1
       

6.  Which mixture of solutions does not produce a solid precipitate?

      
A) silver(I) nitrate and sodium chloride 
B) copper(II) sulfate and potassium carbonate
C) calcium nitrate and sodium sulfide  
D) potassium iodide and lead(II) nitrate
E) sodium hydroxide and cobalt(II) chloride  
     

 7. What is DE for a thermodynamic system that absorbs 200 cal of heat from the surroundings while delivering 100 cal of work?

A) 300 cal 
B) 100 cal  
C) 0
D) -300 cal
E) -100 cal
  

 8. How much heat (J) increases the temperature of 1430 kg of iron from 250C to 800C? 
     The specific heat capacity of iron is 0.450 J/g-
C.

A) 9.94 107 J
B) 5.15 108 J
C) 7.87 108 J
D) 3.54 108 J  
E) 5.20 107 J
   

9.  The oxidation number of sulfur in SO2 is

     A)  7                B)  4           C)  6               D)              E)  5

 


10.  The oxidation number of tellurium in H2TeO42H2O is

     A)  7                B)  4             C)  6             D)  3             E)  5

 


11.  The oxidation number of chlorine in ClO4is    

    A)  7              B)  4             C)  6               D)  3             E)  5

 


12.  The oxidation number of vanadium in H2V4O11 is

     A)  7                B)  4             C)  6               D)  3             E)  5   
  


13.   The zinc ion in the reaction Cu(s) + Zn2+(aq) Cu2+(aq) + Zn(s)  

A) is a spectator ion
B) undergoes oxidation
C) undergoes reduction   
D) none of the above
   

14.  Identify the oxidizing agent in the reaction

                            Pb(s) + PbO2(s) + 2 H+(aq) + 2 HSO4- (aq)   2 PbSO4(s)  + 2 H2O(l)

A)  Pb  
B) H+
C) PbSO4
D) PbO2    
E) HSO4-  

15.   A chemical reaction at constant pressure transfers 200 kJ of heat to the surroundings.
      The enthalpy change of the reaction is best described as:

   
A) DH =   200 kJ (endothermic)
B) DH = -200 kJ (exothermic)   
C) DH = -200 kJ (endothermic)
D) DH =   200 kJ (exothermic)  
E) none of the above
   

16.  Use the reaction  3 C(s) + 4 H2(g)    C3H8(g),   DH = -104 kJ  to determine DH for

                                                 0.5 C3H8(g)    1.5 C(s)  +  2 H2(g),    DH = ?

A) 52 kJ   
B) -208 kJ 
C) 104 kJ
D) -52 kJ
E) 208 kJ   
  

 17.  Classify the reaction:   H2SO4(aq) + Ba(OH)2(aq) 2H2O(l) + BaSO4(s) 

A) oxidation-reduction
B) acid-base neutralization
C) precipitate formation
D) acid-base neutralization and precipitate formation 
E) acid-base neutralization and oxidation-reduction
  

18. Use the heats of formation to find DH for the reaction

                                        8 NH3(g) + 6 NO2(g)    7 N2(g)  + 12 H2O(g)

     

  DHf   

  
A)

  -2734 kJ

N2(g)    0 kJ
B) -3074 kJ NH3(g)    -46 kJ
C) -3470 kJ NO2(g)   33 kJ
D) -3470 kJ H2O(g) -242 kJ
E) -3129 kJ          
     

19.   Find the moles of electrons transferred in the oxidation-reduction reaction

8 NH3(g) + 6 NO2(g)    7 N2(g)  + 12 H2O(g)

                               This type of problem will NOT be covered on the exam.

A) 12
B) 36
C) 18
D) 30
E) 24   
   

20.  How many mL of 1.25 M H2SO4 solution react with 2.77g of aluminum hydroxide by

3 H2SO4  +  2 Al(OH)3     6 H2O  + Al2(SO4)3

A) 36.5 mL
B) 18.9 mL
C) 42.6 mL   
D) 28.4 mL
E) 53.3 mL