The thermal decomposition of a compound is of first order. If 50 % of a sample of the compound decomposes in 120 minutes, how long will it take for 90 % of the compound to decompose?

1. 399 min                                                        

2. 410 min

3. 250 min                                                        

4. 120 min

The half-life for radioactive decay of ${}^{14}C$ is 5730 y. An archaeological artifact containing wood had only 80 % of the ${}^{14}C$ found in a living tree. The age of the sample will be:

1. 1657.3 y                                                

2. 1845.4 y

3. 1512.4 y                                                

4. 1413.1 y

Two substances A and B are present such that $\left[A_0\right] = 4\left[B_0\right]$ and half life of A is 5 minute and that of B
is 15 minute. If they start decaying at the same time following first order kinetics how much time later will the concentration of both of them would be same.

(1) 15 minute                                        

(2) 10 minute

(3) 5 minute                                          

(4) 12 minute

The following data were obtained during the first-order thermal decomposition of $S{O}_{2}C{l}_2$ at a constant volume.

SO₂Cl₂(g) → SO₂(g) + Cl₂(g)

The rate of the reaction when total pressure is 0.65 atm will be:

1. $7.8$ $\times$ ${10}^{-4}$ $s^{-1}$ $atm.$                                  

2. $0.8$ $\times$ ${10}^{-4}$ $s^{-1}$ $atm.$

3. $2.4$ $\times$ ${10}^{-2}$ $s^{-1}$ $atm.$                                   

4. $6.1$ $\times$ ${10}^{-8}$ $s^{-1}$ $atm.$

Assertion : A lump of coal burns at a moderate rate in air while coal dust burns explosively.

Reason : Coal dust contains very fine particles of carbon.

Assertion : Liquid bromine reacts slowly as compared to bromine vapour.

Reason : In liquid bromine, the bromine molecules are held together by a force which is much weaker than the force existing between the two molecules of bromine in the vapour phase.

Assertion : The reaction,

$N_2 \left(10atm\right) 3H_2 \left(10atm\right)\to 2N{H}_3 \left(g\right) is faster.$

Reason : Catalyst lowers the activation energy of the reaction.

Assertion : Molecularity of a reaction cannot be determined experimentally.

Reason : Molecularity is assigned to the reactions on the basis of mechanism.

Assertion : For a first order reaction, the degree of dissocation is equal to $\left(1-e^{-kt}\right)$

Reason  : For a first order reaction, the pre-exponential factor in the Arrhenius equation has the dimension of $tim{e}^{-1}$

At 400 K, the energy of activation of a reaction is decreased by 0.8 kcal in the presence of a catalyst. As a result, the rate will be: