A) While recrystallizing, what should you do if you have solid particles that don’t dissolve even after adding a lot more hot solvent than called for in the procedure? b) What should you do if your crystals don’t come out of solution even after cooling on ice, adding a seed crystal, and scratching for quite a while?

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. because water vapor readily adsorbs onto the surface of silica gel, 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 for δg, δh, and δs for the adsorption of water.