In: Math
A room has volume 100m3, and initially contains normal air. Every minute, 2m3 of gas is pumped in, which is 1.9m3 air, and 0.1m3 xenon. Every minute, 2m3 of well-mixed gas is pumped out. What volume of xenon will be in the room after 1 hour?
Let y(t) be the total volume(in ) of xenon in the room at t minutes.
Gas is pumped into the room at the rate 2 /min which is 1.9 air and 0.1 xenon. So, the rate at which xenon is pumped into the room is 0.1 /min.
The well-mixed gas is pumped out at the rate 2 /min.
The concentration of xenon in the air at time t minutes
So, the rate at which xenon is pumped out of the room is
Hence, the differential equation governing the system is
Since this is a separable differential equation, it can be solved as follows.
where C is the constant of integration.
At time t = 0, the room contains normal air. So, at t = 0, the total volume of xenon in the room is 0 i.e. y(0) = 0. Substituting this initial condition in our equation, we get
Now, the particular solution for the system is
The volume of the xenon in the room after 1 hour i.e. at t = 60 minutes is