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For a first order reaction, the time required for x % completion is exactly 2 times the time required for 90 % completion of the same reaction. The value of x is

Correct answer

99

Step-by-step solution

For a first order reaction, the integrated rate law is given by: t = 2.303 k ( 100 100 - percentage completion ) The time required for 90 % completion is: t_ 90 % = 2.303 k ( 100 100 - 90 ) = 2.303 k (10) = 2.303 k 1 The time required for x % completion is: t_ x % = 2.303 k ( 100 100 - x ) Given that t_ x % = 2 t_ 90 % : 2.303 k ( 100 100 - x ) = 2 2.303 k Cancelling the common terms: ( 100 100 - x ) = 2 100 100 - x = 10^2 = 100 100 - x = 1 x = 99 Answer: 99

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