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QJEEM19Ch3dcd: JEE Main 2019 Chemistry - Class 12 JEEM19Ch3dcd Solution: The reaction 2X B is a zeroth order reaction. If the initial…

The reaction 2X →\to B is a zeroth order reaction. If the initial concentration of X is 0.2 M, the half-life is 6 h. When the initial concentration of X is 0.5 M, the time required to reach its final concentration of 0.2 M will be:

Multiple Choice Options

  • A 18.0 h
  • B 9.0 h
  • C 7.2 h
  • D 12.0 h

Step-by-Step Verified Solution

For zero order reaction,

t1/2 = a02k{{{a_0}} \over {2k}}

⇒\Rightarrow k = a02t1/2{{{a_0}} \over {2{t_{1/2}}}} = 0.22×6{{0.2} \over {2 \times 6}} = 1.67 ×\times 10-2 mol L–1h–1

For zero order reaction,

A0 - At = kt

⇒\Rightarrow 0.5 - 0.2 = 1.67 ×\times 10-2 t

⇒\Rightarrow t = 0.31.67×10−2{{0.3} \over {1.67 \times {{10}^{ - 2}}}} = 18 h

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