Chemical Kinetics

Chemical Kinetics

Question

The time for half life period of a certain reaction A → Products is 1 hour. When the initial concentration of the reactant ‘A’ is 2.0 mol L–1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L–1 if it is a zero order reaction?

  • 1 h 

  • 4 h 

  • 0.25 h 

  • 0.5 h

Answer

C.

0.25 h 

Given that [A]o = 2 mol L-1
straight t subscript 1 divided by 2 end subscript space equals space fraction numerator left square bracket straight A subscript 0 right square bracket over denominator 2 straight k subscript 0 end fraction space or comma space straight k subscript 0 space equals fraction numerator space left square bracket straight A subscript 0 right square bracket over denominator 2 straight t subscript 1 divided by 2 end subscript end fraction
On space putting space the space value comma space we space get
straight k subscript 0 space equals space fraction numerator left square bracket 2 right square bracket over denominator 2 space straight x 1 end fraction space equals space 1
So comma space straight k subscript 0 space equals 1
and space straight k subscript 0 space equals space fraction numerator increment straight X over denominator straight t end fraction
or space straight t space equals space fraction numerator 0.50 minus 0.25 over denominator 1 end fraction space equals space 0.25 space straight h

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