Question 24

Consider a certain reaction A → Products with k = 2.0 x 10^-2 s^-1. Calculate the concentration of A remaining after 100 s if the initial concentration of A is 1.0 mol L^-1.

Answer

k= 2.0 × 110^-2 s^-1

T= 100 s

[A]_o= 1.0 moL ^{- 1}

Since the unit of kis s^{- 1}, the given reaction is a first order reaction.

Therefore, k = 2.303/t Log [A]_º/ [A]

⇒2.0 × 110^-2 s^-1= 2.303/100s Log 1.0/ [A]

⇒2.0 × 110^-2 s^-1= 2.303/100s ( - Log [A] )

⇒ - Log [A] = - (2.0 x 10^-2 x 100) / 2.303

⇒ [A] = antilog [- (2.0 x 10^-2 x 100) / 2.303]

= 0.135 mol L^{- 1}(approximately)

Hence, the remaining concentration of A is 0.135 mol L ^{- 1}.

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