Question

A frist order reaction takes 15 minute to complete 25% how much will it take to complete 65%​

Answer 1

54.72 min

Explanation:

Given: t₁ = 15 min, t₂ = ? [A]₁ = 100 then [A]₂ = 100 - 25 = 75 for 25 %  

            For 65 % [A]₁ = 100 then [A]₂ = 100 - 65 = 35

where  [A]₁ and  [A]₂ are concentration of reactant and product repeactively.

We know that,

k = 2.303/t₁ log₁₀ [A]₁/[A]₂    

  = 2.303/15 log₁₀ 100/75

  = 2.303/15 log₁₀ 1.333

  = 2.303/15 × 0.125

  = 0.01912 / min  

t₂ = 2.303/k log₁₀ 100/35

  = 2.303/0.01912 log₁₀ 2.85

  =  120 × 0.456

  = 54.72 min