The enthalpy change for the adsorption process and micelle formation respectively are

Solution

Chemistry ma’am · 4 steps

Adsorption gives out heat while micelle formation soaks it up, and entropy tells you why.

1. Adsorption. Particles at a surface have unbalanced attractive forces. When gas molecules stick there, those forces are partly satisfied and energy is released, so Δ H_(ads) < 0.
2. Entropy check. Free gas molecules get held on a surface, so their freedom of movement drops and Δ S < 0. For Δ G = Δ H - TΔ S to be negative, Δ H has to be negative.
3. Micelle formation. Soap or detergent ions group together into micelles only above the Krafft temperature, and the process absorbs heat, so Δ H_(mic) > 0. It still happens because entropy rises: the water molecules held around the separate hydrocarbon tails are set free.

   Process	Δ S	Δ H	What makes Δ G < 0
   Adsorption	negative	negative	the heat released
   Micelle formation	positive	positive	the entropy gain, at high enough T

4. So. Δ H_(ads) < 0 and Δ H_(mic) > 0, which is option (d).

The idea to keep. Adsorption always lowers entropy, so it must be exothermic to happen at all. Micelle formation is endothermic and entropy-driven, which is why it needs the Krafft temperature.

Answer from the NTA final answer key. Solution by PrepWiser.