IIT-JEE 2011 · Paper 2 · Chemistry Q11

ChemistryMultiple correct+4Question 11 of 60

For the first order reaction
$\ce{2N2O5(g) -> 4NO2(g) + O2(g)}$

the concentration of the reactant decreases exponentially with time.

the half-life of the reaction decreases with increasing temperature.

the half-life of the reaction depends on the initial concentration of the reactant.

the reaction proceeds to 99.6 % completion in eight half-life duration.

Answer and worked solution

Official answer: A, B, D

First order: $[A]=[A]_0e^{-kt}$ (A) and $t_{1/2}=\dfrac{0.693}k$ , independent of $[A]_0$ (C is false).

Temperature. $k$ rises with temperature (Arrhenius), so $t_{1/2}$ falls (B).

Eight half-lives. Fraction left $=2^{-8}=\frac1{256}=0.39\%$ , so 99.6% has reacted (D).

(A), (B), (D)

Topics:Integrated rate equations Half-life

IIT-JEE 2011 · Paper 2, Chemistry question 11