3.10 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 c½. Find the value of .
Given,
k=1.237×10-2S m-1, c=0.001 M
Then, k=1.237×10-4 S cm-1, c1/2=0.0316 M1/2
∴ Λm=kc
=1.237×10-1 S cm-10.001 mol L-1×1000 cm3L
=123.7 S cm2 mol-1 Given,
k=11.85×10-2 S m-1, c=0.010 M
Then, k=11.85×10-4 S m-1, c1/2=0.1 M1/2
∴ Λm=kc
=11.85×10-4 S cm-10.010 mol L-1×1000 cm3L
=118.5 S cm2 mol-1 Given,
k=23.15×10-2 S m-1, c=0.020 M
Then, k=23.15×10-4 S cm-1, c1/2=0.1414 M1/2
∴ Λm=kc
=23.15×10-4 S cm-10.020 mol L-1×1000 cm3L
=115.8 S cm2 mol-1Given,
k=55.53×10-2 S m-1, c=0.050 M
Then, k=55.53×10-4 S cm-1, c1/2=0.2236 M1/2
∴ k=kc
=55.53×10-4S cm-10.050 mol L-1×1000 cm3L
=111.1 1 S cm2 mol-1 Given,
k=106.74×10-2 S m-1, c=0.100 M
Then, k=1.06.74×10-4 S cm-1, c1/2=0.3162 M1/2
∴ Λm=kc
=106.74×10-4 S cm-10.100 mol L-1×1000 cm3L
=106.74 S cm2 mol-1 Now, we have the following data:
C1/2M1/2 | 0.0316 | 0.1 | 0.1414 | 0.2236 | 0.3162 |
Λm (S cm2 mol-1) | 123.7 | 118.5 | 115.8 | 111.1 | 106.74 |
Since the line interrupts Λm at 124.0 S cm2 mol-1, Λ0m=124.0 S cm2 mol-1
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