Dilute sulfuric acid (19% acid and the rest water) is required for activating car batteries. A tank of weak acid (12.5% acid and the rest water) is available.
If 450 lbs of 78% concentrate acid is added to the tank to get the required 19% acid, how much of the 19% acid is now available?

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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.