Question

If there is initially 1.334 m o2, how long will it take for the o2 concentration to reach 0.443 m?

Answer 1

To answer, we take it that the rate of the consumption of O2 in this item is directly proportional to its concentration in first degree such that, 
                       -dCa/dt  = kCa
Solving,
                    -dCa/Ca = kt
                   lnCa - lnCao = -kt
Substituting,
                   ln(0.443) - ln(1.334) = -k(t)
                            t = 1.1023/k