JEE Advanced2011ChemistryChemical KineticsActual
For the first order reaction 2 ~N ₂ O ₅( ~g ) 4 NO ₂(g)+ O ₂(g)
Options
- Athe concentration of the reactant decreases exponentially with time.
- Bthe half-life of the reaction decreases with increasing temperature
- Cthe half-life of the reaction depends on the initial concentration of the reactant.
- Dthe reaction proceeds of 99.6 % completion in eight half-life duration.
Correct answer
A. the concentration of the reactant decreases exponentially with time.
Step-by-step solution
(a) For a first order reaction, the concentration of reactant remaining after time t is given by [A]=[A]₀ e^ -k t Therefore, concentration of reactant decreases exponentially with time. (b) Rise in temperature increases rate constant (k) and therefore decreases half-life (t_ 1 / 2 ) as t_ 1 / 2 = In 2 k (d) For a first order reaction, if 100 moles of reactant is taken initially, after n half-lives, reactant remaining is given by aligned & Percentage A=100 ( 1 2 )^n=100 ( 1 2 )^8=0.3906 & A reacted =100-0.3906=99.6