Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main20264 April 2026Morning ShiftChemistryChemical KineticsActual

Consider the first order reaction R P . The fraction of molecules decomposed in the given first order reaction can be expressed as

Options

  1. A1 - e^ k₁ t
  2. B1 + e^ k₁ t
  3. C1 + e^ -k₁ t
  4. D1 - e^ -k₁ t

Correct answer

D. 1 - e^ -k₁ t

Step-by-step solution

For a first order reaction, the concentration of reactant at time t is given by [R]_t = [R]₀ e^ -k₁ t The amount of reactant decomposed is [R]₀ - [R]_t = [R]₀ - [R]₀ e^ -k₁ t = [R]₀ (1 - e^ -k₁ t ) The fraction of molecules decomposed is [R]₀ - [R]_t [R]₀ = [R]₀ (1 - e^ -k₁ t ) [R]₀ = 1 - e^ -k₁ t Answer: 1 - e^ -k₁ t

Practice Chemical Kinetics on Quantrex Academy →

More from Chemical Kinetics

For a reversible reaction R P , at constant temperature, both the forward and the backward reactions are first order elementary reactions with rate constants k_f and k_b , respecti 2026For a first-order reaction R P at a given temperature, k is the rate constant. For this reaction, at the given temperature, the concentrations of R and P at a time t are [ R ] and 2026Given below are two statements: R=8.314 J K ⁻¹ mol ⁻¹ and 1 cal =4.2 J Statement I: When E_a=12.6 kcal/mol, the room temperature rate constant is doubled by a 10 ,^ C increase in t 2026Decomposition of a hydrocarbon follows the equation k = (5.5 10¹¹ , s ⁻¹) ,e^ -28000 , K T . The activation energy of reaction is __________ kJ mol ⁻¹ . (Nearest Integer) Given : R 2026For a reaction A P at T K , the half life (t_ 1/2 ) is plotted as a function of initial concentration [A]₀ of A as given below. The value of x in the given figure is _______ s (Nea 2026First order gas phase reaction A B + C p_i = initial pressure of gas A, p_t = total pressure of the reaction mixture at time t Expression of rate constant ( k ) is 2026If the half life of a first order reaction is 6.93 minutes then the time required for completion of 99 % of the reaction will be _____ minutes. (Given : 2 = 0.3010 ) 2026Consider the given graph showing variation of reactant concentration with time. Three different reactions were started with identical initial concentration of reactants. Which of t 2026 Full Chemical Kinetics list All JEE Main PYQs