Which of the following could be the rate equation for a first order reaction? please help this is timed

Rate = k[A] = first order reaction

Given

Rate law

Required

A first-order reaction

Solution

The rate law : equation for the rate of chemical reaction

For reaction

aA + bB ⇒ C

The rate : r = k[A]ᵃ[B]ᵇ

The sum of exponents(a+b) is the reaction order

From the choice :

a. a+b = 2, second order reaction

b. a+b = 3, third order reaction

c. a+b = 4, fourth order reaction

d a+0 = 1, first order reaction

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.