I have been putting some thought into understanding Gibbs energy but I can't quite figure one thing out. Here is my dilemma: Say that someone wants to react A with B to form C, and they mix pure A with pure B. At the moment the reaction starts, there is no C in the mixture (is this correct?). If the reaction quotient is [C]/[A], then shouldn't the reaction quotient equal zero at the beginning of the reaction? If that is the case, then wouldn't the change in Gibbs energy be undefined at the beginning of the reaction if deltaG = deltaG(standard) + RTln(Q)? Thanks for your help!