Question

1.) 2A → B + C

The above reaction is run and found to follow second order kinetics with a rate constant of 1.30 x 10^-3 M^-1sec^-1. If the initial concentration of A is 1.33 M, what is the concentration after 164 seconds?

2.) 2A → B + C

Two trials of the above reaction are run with the same initial concentration of A. The first trial is performed at 25^oC and the second at 35^oC. If the rate constant at 25^oC is 0.434 M/min, what is the rate constant in the second trial if the reaction has an activation energy of 31.3 kJ/mol?

Answer 1

1)

rate constant k = 1.30 x 10^-3 M^-1sec^-1.

initial concentration of A = 1.33 M

time = 164 sec

k = (1/t) { 1/[ A] - 1/ [A₀] } for second order

1.30 x 10^-3 = (1/164) { 1/[ A] - 1/ 1.33 }

[ A] = 1.0361M

concentration after 164 seconds = 1.0361 M

2) rate constant at 25^oC = 0.434 M/min,

reaction has an activation energy = 31.3 kJ/mol

rate constant in the second trial = ?

log(k2/k1) =( Ea/2.303R)[1/T1-1/T2]

log(k2/0.434) =( 31.3 / 2.303 x 8.314 x 10^-3)[1/298-1/308)

k₂= 0.654 M / min

rate constant in the second k₂= 0.654 M / min