Chemical Kinetics

Consider the following transformation involving first order elementary reaction in each step at constant temperature as shown below. [figure] Some details of the above reactions are listed below. [figure] If the overall rate constant of the above transformation (k) is given as k = k1k2k3 and the overall activation energy (Ea) is 400 kJ mol-1, then the value of Ea3 is kJ mol-1 (nearest integer)

Consider the following reaction, the rate expression of which is given below A + B C rate = k[A]1/2[B]1/2 The reaction is initiated by taking 1 M concentration of A and B each. If the rate constant (k) is 4.6 10-2 s-1, then the time taken for A to become 0.1 M is sec. (nearest integer)

The ratio of 14C12C in a piece of wood is 18 part that of atmosphere. If half life of 14C is 5730 years, the age of wood sample is years.

The following data were obtained during the first order thermal decomposition of a gas A at constant volume : A(g) 2B(g) + C(g) [figure] The rate constant of the reaction is 10-2 s-1 (nearest integer)

Integrated rate law equation for a first order gas phase reaction is given by (where Pi is initial pressure and Pt is total pressure at time t)

1. k = 2.303t Pi(2Pi - Pt)
2. k = 2.303t (2Pi - Pt)Pi
3. k = 2.303t Pi(2Pi - Pt)
4. k = 2.303t 2Pi(2Pi - Pt)

r = k[A] for a reaction, 50% of A is decomposed in 120 minutes. The time taken for 90% decomposition of A is minutes.

The rate of a first order reaction is 0.04 mol L-1 s-1 at 10 minutes and 0.03 mol L-1 s-1 at 20 minutes after initiation. Half life of the reaction is minutes. (Given 2 = 0.3010, 3 = 0.4771)

NO2 required for a reaction is produced by decomposition of N2O5 in CCl4 as by equation 2N2O5(g) 4NO2(g) + O2(g) The initial concentration of N2O5 is 3 mol L-1 and it is 2.75 mol L-1 after 30 minutes. The rate of formation of NO2 is x 10-3 mol L-1 min-1, value of x is . (nearest integer)

For a reaction taking place in three steps at same temperature, overall rate constant K = K1 K2K3. If Ea1, Ea2 and Ea3 are 40, 50 and 60 kJ/mol respectively, the overall Ea is kJ/mol.

The half-life of radioisotope bromine - 82 is 36 hours. The fraction which remains after one day is 10-2. (Given antilog 0.2006 = 1.587)