Question

a first order reaction is 10% complete in 20 minutes the time taken for 19% completion is ​

Answer 1

Time taken for 19% completion of a first order reaction which takes 20 minutes for 10% completion is equal to 40 minutes.

• For a first order reaction, the integrated rate law is kt = ln(Ai/At)
• When reaction is 10% completed At= 0.9 Ai, k = ln(10/9)/20 min⁻¹
• The value of k remains constant for a given reaction and is a function of temperature only.
• When reaction is 19% completed, At= 0.81Ai, t = ln(100/81)/k
• Putting the value of K obtained we get t to be equal to 40 minutes.