[physstudent1]

I don't understand how I can tell which side of the equilibrium the reaction will lie apparently it is different depending on if trace acid is used or if aqueous acid is used.  I am assuming trace acid is very small amounts of acid.  can someone please help me to determine if reactions like this will be on the side of the cyclic hemiacetal or the hydroxyalkanal, I dont understand how trace acid or aqueous acid will make a difference

[nj_bartel]

I believe conc aqueous acid favors products and dilute aqueous acid favors reactants.