A sample of NO2 occupies 16,500 mL at STP. How many NO2 molecules are in the sample?
1. 5.88 × 1022 NO2 molecules
2. 9.11 × 1023 NO2 molecules
3. 7.65 × 1025 NO2 molecules
4. 4.43 × 1023 NO2 molecules
5. 2.00 × 1024 NO2 molecules

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.