If the volume of the vessel in which the reaction

2NO + O₂ → 2NO₂

is occurring is diminished to 1/3rd of its initial volume. The rate of the reaction will be increased by

• 3 times

• 9 times

• 27 times 

• 36 times

The half-life period of radioactive element is 140 days. After 560 days, 1 gram of element will reduce to

• 1/2 g

• 1/4g

• 1/8 g

• 1/16g

In a chemical reaction two reactants takes part. The rate of reaction is directly proportional to the concentration of one of them and inversely proportional to the concentration of the other. The order of reaction is :

• 0

• 1

• 2

• 4

If the rate constant for a first order reaction is k, the time (t) required for the completion of 99% of the reaction is given by:

• t = 6.909/k

• t = 4.606/k

• t = 2.303/k

• t = 0.693/k