In: Chemistry
The specific rate constant for the first-order decomposition of N2O5(g) to NO2(g) and O2(g) is 7.48×10−3s−1 at a given temperature.
A. Find the length of time required for the total pressure in a system containing N2O5 at an initial pressure of 0.100 atm to rise to 0.150 atm .
B. Find the length of time required for the total pressure in a system containing N2O5 at an initial pressure of 0.100 atm to rise to 0.200 atm .
C. Find the total pressure after 110 s of reaction.
Answer – We are given, first order reaction –
N2O5(g) -----> NO2(g) + O2(g) , rate constant , k = 7.48*10-3 s-1
A) In this one there is given, Ao = 0.100 atm , At = 0.150 atm, t = ?
We know first order integrated law –
ln At / Ao = -k*t
ln 0.150 /0.100 = -7.48*10-3 s-1 * t
0.405 = -7.48*10-3 s-1 * t
So, t = 54.21 s
B) In this one there is given, Ao = 0.100 atm , At = 0.200 atm, t = ?
We know first order integrated law –
ln At / Ao = -k*t
ln 0.200 /0.100 = -7.48*10-3 s-1 * t
0.405 = -7.48*10-3 s-1 * t
So, t = 92.67 s
C) We know Ao = 0.100 atm , t = 110 s, so
ln At / Ao = -k*t
ln At /0.100 = -7.48*10-3 s-1 * 110 s
= -0.823
Taking antiln from both side
At /0.100 = 0.439
At = 0.100 atm * 0.439
= 0.0439 atm
So total pressure after 110 s of reaction = 0.100+0.0439
= 0.144 atm