BirZeit University Chemistry Department Chemistry 132  

 

 

 

 

 


First Hour Exam                             

1)   Which equation correctly describes the relationship between Kp and Kc for the reaction below?

4 NH3(g) + 3 O2(g) Û   2 N2(g) + 6 H2O(g)

 

a)  Kp = Kc                                         b)  Kp = Kc (RT)                 c)  Kp = Kc (RT)-1
d)  Kp = Kc (RT)7/8                        e)  Kp = Kc (RT)8/7

 

2)  Which of the following reactions lead to an increase in the entropy of the system?

a)  3Cl2(g)  +  2 Al(s)    Û     Al2Cl6(s)

b)  Li2O(s)  +  CO2(g)   Û      Li2CO3(s)

c)  N2(g)   +  3H2(g)      Û     2NH3(g)

d)  2Mg(s)  + O2(g)       Û     2MgO(s)

e) none of the above.

 

3) What is the equilibrium constant (K) for the reaction below at 600 K ?

2 CH4(g) Û  C2H6(g) + H2          DG°rxn = + 72.3 kJ/mol

a)  2.0 x 10+6                  b)  0.99        c)  5.1 x 10-7
d)  2.1 x10-13                  e)  3.2 x 10-15

 

4) Which manipulation(s) will shift the equilibrium to the right?

The reaction is exothermic (DHrxn < 0)

CO2(g) + H2(g)   Û  CO(g) + H2O(g)

(1) increasing the concentration of H2

(2) decreasing the reaction temperature
(3) increasing the reaction volume
(4) removing H2O from the system
(5) increasing the concentrations of H2 and CO2

a) 1, 2, 3, 4, 5        b) 1, 4, 5      c) 1, 3, 4, 5  d) 1, 2, 4, 5            e) 3 only

 

5) For a particular process q= 20kJ and w = 15 kJ. Which statement is true?

a) Heat flows from the system to the surroundings.

b)The system does work on the surroundings.

c) DE = 35 kJ

d) All of the above are true

e)None of the above are true.

 

6) A reaction has a (-) DH°rxn and (-) DS°rxn. This reaction will ...

a)  be spontaneous at low T
b)  be spontaneous at high T
c)  be spontaneous at all temperatures.
d)  not be spontaneous at any temperature.
e)  need more information to predict spontaneity.

 

 

 

7) For the following process,

          Br2(l)   Û 2Br(g)

      a.   DH is + and  DS is + for the reaction.

      b.   DH is - and  DS is - for the reaction.

      c.   DH is + and  DS is - for the reaction.

      d.   DH is - and  DS is + for the reaction.

      e.   DG is + for all temperatures.

 

8) For the hypothetical reactions 1 and 2 below, K1 = 103 and K2 = 10-5.

        1. A + 2B   Û   AB2

        2. A + B Û   AB

        3. AB2   Û   AB + B

The value of K for reaction 3 would be:

a) K3  = 10-8             b) K3   = 10-2           c) K3   = 102

d) K3   = 108                    e) none of these

 

9) A solution consisting of 0.200 mol of methylbenzene (C6 H5 CH3 ) in 250.g of nitrobenzene (C6 H5 NO ) freezes at 0.40 oC.  Pure nitrobenzene freezes at 6.0oC .  The molal freezing-point constant of nitrobenzene is

a) 1.8 oC mo  .   b) 3.5 oC m      c) 5.6 oC m      d) 7.0 oC m      e) 14.0 oC m

 

10) Given the equilibrium reaction:

A + B     Û      C + D + heat.

 What change in the reaction system will change the value of the equilibrium constant?

a) an increase in the concentration of A and B;

b) an increase in the concentration of C and D;

c) an increase in temperature;

d)  an increase in pressure by adding inert gas.

 

11) An aqueous solution of hydrogen peroxide is 30.0% H2O2 by mass and has a density of 1.11 g/cm3  The MOLARITY of the solution is:

a) 7.94 M      b) 8.82 M      c) 9.79 M      d) 0.980 M              e) none of these

 

12) What is the mole fraction of ethanol, C2 H5 OH, in a methanol solution that is 40.% methanol, CH3 OH, by mass?

a) 0.40             b) 0.46             c) 0.51             d) 0.54             e) 0.60

 

13)                                 Vapor pressure

                                    (in torr) at 25o C

benzene (C6H6)                    94.4

chloroform (CHCl3)             172.0

 

Using the above data, calculate the total vapor pressure of a chloroform-benzene solution at 25oC which contains 50.0 g CHCl3 and 50.0 g C6H6.  Assume the solution behaves ideally.

a) 67.8 torr             b) 125 torr              c) 148 torr              d) 172 torr

 

 

14) Which of the following concentrations can change with a change in temperature?

         1.  molality

         2.  molarity

         3.  mole percentage

      a)  1 only    b)  2 only          c)  3 only          d)  1 and 2 only            e)  2 and 3 only

 

15). What is the equilibrium concentration of NO when the

initial concentration of N2 was 0.100M and O2 was 0.090 M?

Kc= 3.3 x 10-10 at this temperature.

N2(g) + O2(g) Û2 NO(g)

 

a) 1.48 x 10–12 M                b) 8.62 x 10–7 M       c) 1.72 x 10–6 M

d) 2.44 x 10–6 M                 e) 3.45 x 10–6 M

 

16) What is the vapor pressure of an aqueous solution at 75 oC containing 60.0 g of urea(molecular weight 60.0 g/mol) in 180. g of water.Given that the vapor pressure of water at 75o C is 290. MmHg.

 a).  29 mmHg.             b)  100 mmHg. c)  153 mmHg.

 d).  190 mmHg.                       e)  264 mmHg.

 

17) Calculate the molecular weight of a small protein if a 0.20-g sample dissolved in 100 mL of water has an osmotic pressure of 9.8 mmHg at 25.0 C.

a).  3.5 x 103  g/mol      b)  3.8 x 103  g/mol        c)  4.0 x 103  g/mol                

d)  4.5 x 103  g/mol       e)  none of these

 

 

MW

C2H5OH

46 g/mol

CH3OH

32g/mol

C6H6

78.0 g/mol

CHCl3

119.5 g/mol

H2O2

34.0 g/mol

 

R = 8.314 JK mol-1

R = 0.0821 Latm K mol-1