Assertion :Surfactant molecules form micelles above the critical micelle concentration (CMC). Reason: The conductance of solution of surfactant molecules decreases sharply at the (CMC).
Assertion :Surfactant molecules form micelles above the critical micelle concentration (CMC). Reason: The conductance of solution of surfactant molecules decreases sharply at the (CMC).
The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
The critical micelle
concentration CMC is the surfactant concentration at and above which micelles
are formed. It can be determined for surfactant solutions by measuring the
surface tension at different concentrations. Below the CMC the surface tension
decreases with increasing surfactant concentration as the number of surfactants
at the interface increases. Above the CMC, in contrast, the surface
tension of the solution is constant because the interfacial surfactant
concentration does not change any more. In a logarithmic representation of the
surface tension versus the surfactant concentration there are two linear regimes
below and above the CMC. An extrapolation of respective regression lines yields
the CMC at the intersection.
Hence B is answer.
The critical micelle concentration CMC is the surfactant concentration at and above which micelles are formed. It can be determined for surfactant solutions by measuring the surface tension at different concentrations. Below the CMC the surface tension decreases with increasing surfactant concentration as the number of surfactants at the interface increases. Above the CMC, in contrast, the surface tension of the solution is constant because the interfacial surfactant concentration does not change any more. In a logarithmic representation of the surface tension versus the surfactant concentration there are two linear regimes below and above the CMC. An extrapolation of respective regression lines yields the CMC at the intersection.
Hence B is answer.
