Final answer:
To determine the entropy change for HCl freezing, the enthalpy of fusion and the temperature are needed. Entropy generally decreases when a liquid becomes a solid.
Step-by-step explanation:
The question asks us to determine the entropy change when 2.90 mol of HCl freezes at atmospheric pressure. To find this change in entropy, ΔS, we would use the formula: ΔS = qrev/T, where qrev is the reversible heat exchange and T is the temperature in Kelvin. For the phase transition of freezing, qrev corresponds to the enthalpy of fusion. Unfortunately, the specific enthalpy of fusion for HCl is not provided, so we cannot give a numeric answer. Generally, entropy decreases when a substance transitions from a liquid to a solid because the molecules in a solid are more ordered than in a liquid.