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I think I understand the formulas to calculate this I have seen in my textbook and on this site (e.g peak area/conc.), my problem is that we aren't given the weight or concentration of substance injected.  I'm wondering if this means I should assume the concentrations were identical (they are all of different dichlorobutanes produced in an experiment we did) or if I should instead consult some outside table.

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I think I figured it out!!!   All the dichlorobutanes are going to have the same response factor because of their identical molecular weights.  I guess the subtler differences in shape and polarity will not effect the rf.