[curiouscat]

Suppose I've a reactant R that forms several products A / B / C / D.

R A , R B are all parallel reactions.

The Molecular Weights of R, A, B, C etc. are all known.

R / A / B / C etc. are all in the same phase and the weight fractions at end of reaction are known. Is there an analytical expression I can derive to get the fraction of R that reacts via each reaction?

I wrote out the equations but I can't seem to get an analytical equation but a set of parallel, linear equations that I must solve numerically.

[mjc123]

If you know the weight fractions and molecular weights, the mole fraction is proportional to WF/MW.
Assuming no side or cross reactions, the fraction of R that reacts to give A is
F_A = (W_A/M_A)/(W_R/M_R + W_A/M_A + W_B/M_B ...)

[curiouscat]

If you know the weight fractions and molecular weights, the mole fraction is proportional to WF/MW.
Assuming no side or cross reactions, the fraction of R that reacts to give A is
F_A = (W_A/M_A)/(W_R/M_R + W_A/M_A + W_B/M_B ...)

Indeed! I think that works.

I must have messed the math up. Thanks. I will double check why I got twisted up.