Question

200 g of a reactant becomes100 g in 13.86hr . If the reaction follow 1st oreder . Then weight of reactant left after 46. 12 hrs is

Answer 1

Given:

Initial amount of reactant = 200 gm

Final amount of reactant = 100 gm

Time taken = 13.86 hrs

Order of reaction = 1

Total Time = 46.12 hrs

To Find:

Weigh of reactant left after 46.12 hrs.

Calculation:

- Since the amount of reactant gets halved during 13.86 hrs, so it is the half life of the reaction.

⇒ T1/2 = 13.86 hrs

- Since it is a first order reaction, we have:

k = 0.693/T1/2

⇒ k = 0.693 / 13.86 = 0.05

- Using the first order integrated rate equation, we get:

k = (2.303/t) log ([R]₀/[R])

⇒log ([R]₀/[R]) = kt/2.303

⇒log ([R]₀/[R]) = (0.05 × 46. 12) / 2.303

⇒log ([R]₀/[R]) = 1

⇒ [R]₀/[R] = antilog 1

⇒ [R]₀/[R] = 10

⇒ [R] =  [R]₀/10

⇒ [R] = 200/10

⇒ [R] = 20 gm

- 20 gm reactant is left after 46.12 hrs.