Possibly Useful Physical Constants






Possibly Useful Equations
   and         and    
For an aqueous solution at 25 oC ,   m   (in this equation is not the electrical conductivity)
    and    

and       where
  and

 



1.
The limiting ionic conductivities of the hydrogen ion and of the butyrate anion, at 25 °C, are and respectively. The specific conductivity of a 0.001 M butyric acid solution is . The pH of this butyric acid solution is:
A.
3.94
B.
2.51
C.
4.11
D.
3.30
E.
1.15


2.
Calculate the ionic strength of a solution that is 0.003 M in Mg(NO3)2 , 0.007 M in K2SO4 and 0.005 M in MgSO4 .
A.
0.05 mol dm-3
B.
0.31 mol dm-3
C.
0.03 mol dm-3
D.
0.11 mol dm-3
E.
0.07 mol dm-3


3.
The effective ionic radii of lithium (Li+) and strontium (Sr2+) are 0.59 pm and 1.18 pm respectively. Based on the use of these effective radii in the Born model the ratio of the Gibbs energy of solvation of the lithium ion relative to the strontium ion is:
A.
0.5
B.
1.0
C.
1.5
D.
2.0
E.
2.5


4.
A 0.001 M solution of hydrochloric acid (HC1, strong acid) obeys the Debye Huckel limiting law. The most correct value for its pH is:
A.
3.016
B.
3.000
C.
2.100
D.
5.016
E.
4.000


5.
At 25 °C the solubility product of silver chloride (AgCl) in water is. Calculate the solubility of AgCl in an aqueous 0.01 M MgSO4 solution, using the mean activity coefficient calculated from the Debye-Huckel limiting law.
A.
B.
C.
D.
E.


6.
The Debye-Hückel screening length in a 0.00100 molal solution of NaCl in water at 298 K is:
A.
9.61 nm
B.
6.60 nm
C.
10.4 nm
D.
5.72 nm
E.
18.2 nm


7.
The aqueous solutions of the salts listed in the following choices are all molal and dissociate completely. The solution with the highest is:
A.
Ca (NO3)2
B.
K Cl
C.
Zn SO4
D.
Al PO4
E.
K [Fe (NH3)2(CN) 4]


8.
The solubility of AgCl in water at 298 K is 1.274×10–5 mol L–1. On the assumption that the Debye-Hückel limiting law applies, calculate the ΔG° for the process,
AgCl(s) →Ag+(aq) + Cl–(aq).
taking .
A.
55.9 kJ mol–1
B.
30.2 kJ mol–1
C.
62.5 kJ mol–1
D.
75.3 kJ mol–1
E.
123 kJ mol–1


9.
Consider the following dissociation equilibrium,
Zn(s) ƒ Zn2+ (aq) + 2e–.

When a Zn electrode is partially immersed in a 1 molal ZnSO4 solution the electrical potential developed between the Zn electrode and a point in the solution is +0.762 V. Calculate the electrochemical potential difference (also the Gibb's energy difference) between the two phases assuming a unit activity coefficient for the solute.
A.
B.
C.
D.
E.


10.
The standard potential for the cell in which the overall reaction
Mn(s) + Cl2(g) → MnCl2(aq),

occurs at 25°C is 2.54 V. Given that,
Cl2   +   2 e– →    2Cl–                     Eo = 1.36 V
obtain the standard reduction potential for the manganese(II) ion.
A.
–1.18 V
B.
+1.18 V
C.
+1.36 V
D.
+ 3.24V
E.
–3.24 V


11.
The standard cell potentials for an electrochemical reaction involving a single electron transfer are 0.540 V at 25 0C and 0.610 V at 50 0C. The entropy change for the reaction is estimated to be:
A.
B.
C.
D.
E.


12.
Determine the potential of the cell,
Sn(s) | Sn2+(aq, a = 0.011 ) || Ag+(aq, a = 1.35 M) | Ag(s)
     
         at 25 0C given,
   and  
A.
B.
C.
D.
E.


13.
A piece of metal is placed in each of three beakers containing 1.0 molal
   .
Beaker
Solution
Metal
1
2
3

Given
Reaction

Copper precipitates spontaneously in
A.
beaker 1 only.
B.
beaker 2 only.
C.
beaker 3 only.
D.
beakers 2 and 3.
E.
beakers 1, 2 and 3.


14.
You may need the following figure for some parts of this question.

Which of the following choices is correct
A.
In region B the solubility of an electrolyte decreases as increases.
B.
In region B the solubility of an electrolyte increases as increases.
C.
In region A the solubility of an electrolyte decreases as increases.
D.
The Debye Huckel limiting law is only valid for weak electrolytes.
E.
The relaxation effect increases the conductivity of an electrolyte.


15.
An electrochemical cell is made by placing the two half-cells made of   copper/copper nitrate and silver/silver nitrate in electrical contact using a salt bridge. Given that,
       and        
which of the following occurs spontaneously?
A.
The mass of the copper electrode increases.
B.
The mass of the silver electrode increases.
C.
The mass of the copper electrode decreases.
D.
Copper is deposited on the silver electrode.
E.
The concentration of increases.


16.
OLE2:END::BE580057.OLE2      
The potential of the half-cell when and is:
A.
– 1.365 V
B.
– 1.404 V
C.
1.352 V
D.
1.311 V
E.
1.404 V


17.
Given the following reduction reactions and values:

         

   Calculate for,
         
A.
– 0.744 V
B.
– 0.506 V
C.
0.506 V
D.
– 2.233 V
E.
2.233 V


18.
Given,

         
   
  and



  calculate , the standard Gibbs energy of formation .
A.
B.
C.
D.
E.


19.
At 298.15 K the standard potential for a cell is 1.442 V and
. Given that for the cell reaction calculate .
A.
B.
C.
D.
E.


20.
Given the following standard reduction half-cell potentials at 25 oC ,
 

calculate the solubility product for .
A.
B.
C.
D.
E.


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