Upon freezing aqueous solutions, dissolved solutes are forced into small liquid regions within the frozen ice. This phenomenon affects solute concentrations, solution pH and can accelerate reaction kinetics. The ability to predict this behavior quantitatively has significant implications in environmental and biological studies. For a system with rapid reversible reactions like acids and buffers, a liquid volume decrease thermodynamically necessitates multiple equilibrium shifts which heretofore have been largely unaccounted for in freeze chemistry studies. Herein it is shown that multiple equilibrium shifts explain observed concentration changes of ions and pH shifts both qualitatively and quantitatively within the liquid region of ice upon freezing. Apparent charge imbalances upon freezing are often interpreted as being due to ions becoming trapped within the ice matrix. However, the results herein show that multiple equilibrium shifts allow charge balance to be maintained within the liquid regions of ice while solute concentrations and pH vary upon freezing. It is also shown that for species involved in reversible reactions, concentrations can dramatically increase and/or decrease upon freezing, questioning the common "freeze concentration" assertion that freezing only gives rise to increases in solute concentrations in the absence of solute trapping in the solid ice matrix. The combination of in situ spectroscopy and the multiple equilibrium shift model developed herein can be extended to other systems to help elucidate the effects of freezing on solution pH, solute concentrations and reaction kinetics important in environmental chemistry and cryopreservation. (C) 2018 Elsevier B.V. All rights reserved.