In the extraction of salicylic acid from water using dichloroethane, a student begins with 2.4 grams of the salicylic acid dissolved in 100 ml of water. after extraction with 20 ml of dichloroethane, drying and evaporation of the organic layer yielded 1.344 grams of salicylic acid. assuming the student was efficient and did not lose any material, what is the distribution coefficient (kd) for the system ? let kd = (concentration in organic solvent) / (concentration in aqueous solvent)

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.