Calcium chloride, CaCl2, is used in “hot packs”. When the solid is mixed with water, the products are favored. Based on this information, which of the following is true for the values of ΔH and ΔS for the dissolving process?

CaCl2 (s) → Ca2+ (aq) + 2 Cl− (aq)

A)ΔH is positive ΔS is equal to zero
B)ΔH is negative TΔS must be positive
C)ΔH is positive ΔS is positive
D)ΔH is positive ΔS is negative
E)ΔH is negative TΔS is small compared with ΔH

An exothermic reaction has dH - so it must be B or E

I agree with DrBob222's response it's an exothermic reaction because the temp rises so B or E

To determine the values of ΔH (enthalpy change) and ΔS (entropy change) for the dissolving process of calcium chloride (CaCl2), we can analyze the given information.

In the dissolving process, the solid CaCl2 is dissociated into its constituent ions in water:

CaCl2 (s) → Ca2+ (aq) + 2 Cl− (aq)

We know that the products (Ca2+ and Cl− ions in solution) are favored, which indicates that the dissolving process is spontaneous.

When a process is spontaneous, the Gibbs free energy change (ΔG) is negative. The relationship between ΔG, ΔH, and ΔS is given by the equation:

ΔG = ΔH - TΔS

Where T is the temperature in Kelvin.

Since the dissolving process of CaCl2 is spontaneous, ΔG must be negative. When ΔG is negative, two possibilities arise:

1. If ΔH is negative and TΔS is positive, then the negative term of -TΔS will dominate, making ΔG negative. This corresponds to an exothermic (negative ΔH) process where the increase in entropy (ΔS) is significant enough to overcome the positive contribution of enthalpy.

2. If ΔH is positive and TΔS is relatively small compared to ΔH, then the positive enthalpy change (ΔH) dominates, making ΔG negative. In this case, the entropy change (ΔS) does not contribute significantly to the negativity of ΔG.

Based on this analysis, we can conclude that the correct option is:

E) ΔH is negative, and TΔS is small compared with ΔH.

It is important to note that ΔH alone cannot be determined from the given information. We can only infer the relation between ΔH and ΔS relative to each other and their impact on the spontaneity of the dissolving process.