The air in a room with volume 180m^3 initially contains 0.20% carbon dioxide. Air with only 0.07% carbon dioxi

Question

The air in a room with volume 180m^3 initially contains 0.20% carbon dioxide. Air with only 0.07% carbon dioxide flows into the room at 2m^3 per minute, and the mixed air flows out at the same rate. Find the percentage of carbon dioxide in the room as a function of time. What is the percentage of the carbon dioxide in the room after half an hour?

Answer 1

Allow me to cheat a little. The "residance time" of air in the room is 90 minutes. For this type problem, this is the time for the conc to drop from 0.2 pct CO2 to 0.07+0.39*0.13 or about 0.12 pct; sometimes called the e-th life.