It depends upon if you're an extremely competitive and well-rounded applicant or not. If you have a phenomenal & outstanding profolio, meaning have
(1) 2+ first authored or second authored original research publications in a high-impact journal
(2) have at least a prestigious national grant, or fellowship or scholarship
(3) summer internship at prestigious/well-known places
(4) oral presentations or poster sessions at national/international conferences
(5) teaching assistantship or research assistantship (for a minimum of 1 yr)
(6) volunteer experience within the chemistry community (i.e. outreaching)
(7) 90 percentile on GRE, GPA, or chemistry GRE
(8) number of high-advanced level chemistry courses taken.
If you do indeed have a very strong profolio and letters of recommendation, then you should be expecting to hear back as early as December . The deadline for schools to make a decision is April 15th, 2013.