The first order rate constant of the gas-phase decomposition of dimethyl ether, (CH3 )2O(g) --> CH4 (g)+ H2(g)+ CO(g) is 3.2 *10-4 s-1 at 450 C . The reaction is carried out in a constant volume container. Initially, only dimethyl ether is present, and the pressure is 0.350 atm. What is the pressure after 8.0 min? Assume ideal gas behavior.
Answer – Given, rate constat, k = 3.2*10-4 s-1 , Pi = 0.350 atm, time, t = 8.0 min
We need to convert the time min to s
We know,
1 min = 60 s
So, 8.0 min = ?
= 480 s
We know the formula for the first order
ln Pt / Pi = - k *t
ln Pt / 0.350 atm = - 3.2*10-4 s-1 * 480 s
= - 0.1536
So taking antiln form both side
Pt / 0.350 atm = 0.858
So, Pt = 0.350 atm * 0.858
= 0.300 atm
the pressure after 8.0 min is 0.300 atm
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