COMEDK2025ChemistryChemical KineticsActual
Choose the correct statement.
Options
- AMolecularity of a chemical reaction is always greater than order of the reaction.
- BThe plot of [A] versus time "t" for a zero order reaction is a horizontal line parallel to the x -axis which r
- CFor a first order reaction the time taken for 3 / 4^ th completion is 2 times the half-life period.
- DFor a second order reaction the rate of reaction with respect to reactant becomes 27 times when its concentrat
Correct answer
C. For a first order reaction the time taken for 3 / 4^ th completion is 2 times the half-life period.
Step-by-step solution
Molecularity is the number of reacting species taking part in an elementary reaction and is always a positive integer, whereas order of reaction can be fractional or zero. Thus, molecularity is not always greater than the order of reaction. For a zero order reaction, the rate law is [A] = [A]₀ - kt . The plot of [A] versus t is a straight line with a negative slope -k and y-intercept [A]₀ , not a horizontal line. For a first order reaction, the half-life is t_ 1/2 = 2 k . The time for 3/4^ th completion is t_ 3/4 =