Given a 2nd order rate constant (r = kC2 from the units) the integrated rate law is 1/C0-1/C = kt
From the IGL we know that C = n/V = P/RT, so (for const T)
C = 1/(1/C0 - kt) and P/RT = 1/(RT/P0 -kt) and P = 1/(1/P0 - kt/(RT))
Use 35/760 atm for P0, .082 for R and .015 s for t
Please consider a tutor. Take care.