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NCERT Class XII Chemistry
Chapter - Electrochemistry
Questions with Solutions

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Question : 10
Total: 32
The conductivity of sodium chloride at 298 K has been determined at different concentrations and the results are given below :
 Concentration/M  0.001  0.010  0.020  0.050  0.100
 102×κ∕S m−1  1.237  11.85  23.15  55.53  106.74
Calculate Λm for all concentrations and draw a plot between Λm and c1∕2.Find the value of Λ0m.
Solution:  
1S cm−1=100 Sm−1 ,
1S cm−1
100 S m−1
=1 (unit conversion factor)
 Conc. (M)   κ(S m−1)   κ(S cm−1)   Λm=
1000×κ
‌Molarity
 (S cm2 mol−1 ) 		  c1∕2(M1∕2 )
  10−3   1.237× 10−2  1.237× 10−4  
1000×1.237×10−4
10−3
=123.7 		  0.0316
 10−2   11.85× 10−2  11.85× 10−4  
1000×11.85×10−4
10−2
=118.5 		  0.100
  2×10−2   23.15× 10−2  23.15× 10−4  
1000×23.15×10−4
2×10−2
=115.8 		  0.141
  5×10−2   55.53× 10−2  55.53× 10−4  
1000×55.53×10−4
5×10−2
=111.1 		  0.224
  10−1   106.74× 10−2  106.74× 10−4  
1000×106.74×10−4
10−1
=106.7 		  0.316
Λ0= Intercept on the Λm axis =124.0Scm2mol–1 (on extrapolation to zeroconcentration).
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