$7.$In RTD analysis, the second moment represents:

A$)$ The mean residence time

B$)$ The variance of residence times

C$)$ The skewness of the distribution

D$)$ The kurtosis of the distribution

What does the C curve represent in RTD analysis?

A$)$ The distribution of residence times

B$)$ The cumulative distribution of residence times

C$)$ The frequency of residence times

D$)$ The mean residence time

Which moment of RTD is directly related to the variance of residence times?

A$)$ First moment

B$)$ Second moment

C$)$ Third moment

D$)$ Fourth moment

What is the shape of the C curve for an ideal plug flow reactor?

A$)$ Exponential

B$)$ Gaussian

C$)$ Uniform

D$)$ Parabolic