Wk.5 Thermodynamics #10

[Jaclyn Padilla]

The small bags of silica gel you often see in a new shoe box are placed there to control humidity. Despite its name, silica gel is a solid. It is a chemically inert, highly porous, amorphous form of SiO2. Water vapor readily adsorbs onto the surface of silica gel, so it acts as a desiccant.

Despite not knowing mechanistic details of the adsorption of water onto silica gel, from the information provided, you should be able to make an educated guess about the thermodynamic characteristics of the process. Predict the signs of ΔG, ΔH, and ΔS.
Predict sign of delta G, delta S, and delta H.

[Jaclyn Padilla]

So deltaG would be less than 0 since the absorption of water occurs spontaneously. Delta S is decreases in entropy since molecules move from a gaseous state to a sold phase. Lastly, delta H is less than 0 because in order to make TdeltaS favorable H would need to be negative.

[Damin Rawlins 3B]

Since silica gel adsorbs water vapor, we can assume that the process is spontaneous, meaning that ΔG is negative. When water vapor adsorbs onto the surface of silica gel, it is releasing energy, indicating an exothermic process. This means we can predict that ΔH is negative. When water molecules adsorb onto the surface of silica gel, the total entropy of the system is expected to decrease as the water molecules are confined to the surface of the solid. This leads us to assume that ΔS is negative.