Hey there,
(a) Based on memory, Coca-Cola is like 89% water. The water molecules expand in freezing temperatures. On a molecular scale, the hydrogen atoms in water molecules are attracted to oxygen atoms in nearby water molecules, forming a rigid structure as the water forms ice crystals. The rigid structure takes up more space than those same molecules did as a liquid, causing the ice in the soda container to expand and force out the CO2 inside it in the process. Also, the pressure of CO2 increases as it gets cooler, which also contributes to a potential soft-drink can explosion.
(b) CO2 + H2O <-> H2CO3 <-> HCO3- + H+
(Alkali = basic) An example of an alkai is NaOH. OH- ions neutralize H+ ions and cause a shift towards the products side (right).
This increases H+ ions, decreases pH and increases solubility of CO2 in water.