Chemical Kinetics

The thermal decomposition of ammonium nitrate (NH₄NO₃) does not produce dinitrogen. Instead, it decomposes to form nitrogen oxides like NO₂ and N₂O (nitrous oxide), and water. The other reactions in the options do produce dinitrogen (N₂), typically through the decomposition of azides or by the reaction of ammonium salts with certain reagents.

The correct option is (E) : Thermal decomposition of ammonium nitrate

For a first-order reaction, the relationship between the fraction of the reaction completed, the time, and the half-life is given by the formula: Where:
is the initial concentration,
is the concentration after time ,
is the rate constant,
is the time.
We are given that the half-life is 20 minutes, and for a first-order reaction, the half-life is related to the rate constant by the equation: Thus, the rate constant can be calculated as: To find the time required for 99.9% completion, we need the reaction to go from to 0.1% of . This means . Substituting into the first-order rate equation: Simplifying:

The correct option is (B) :

The rate of decrease in the concentration of A is given by the change in concentration over time. The change in concentration is: The time interval is given as 20 minutes. Therefore, the rate of decrease in concentration is: Thus, the rate of decrease in [A] is 0.015 mol L min .

The correct option is (B) :

Plot (P): The rate decreases over time, but it's not a constant rate. The rate starts high and gradually decreases, approaching zero. This suggests a reaction where the rate depends on the concentration of reactants, and as reactants are consumed, the rate slows down. This is characteristic of a first or higher order reaction, not zero-order. Further, there is no reverse reaction so it is irreversible

Plot (Q): This plot clearly shows both forward and backward reaction rates. The rates converge to a point where the forward and backward rates are equal, indicating equilibrium. This is a reversible reaction. It is not zero order, since it is not linear.

Plot (R): The rate is constant until some of it disappears, then remains constant.

This is an odd reaction, but fits the graph for a zero order reaction.

Therefore, the correct combination is (D) P = Irreversible; Q = Reversible; R = Zero order

Given parameters:

• Rate constant
• Initial concentration
• Time
• Zero-order reaction kinetics

Zero-order rate equation:

Thus, the correct option is (B): 0.2 M.

Step 1: From the data, doubling the concentration of from 0.30 to 0.60 (while keeping constant) results in quadrupling the rate, indicating a second-order dependence on .
Step 2: Increasing concentration from 0.30 to 0.60 (while keeping constant) doubles the rate, indicating a first-order dependence on .
Step 3: The total order of the reaction is .
Step 4: Thus, the total order is 3, and the order in is 1.

Step 1: A pseudo first order reaction appears to be first order because one reactant is in such excess that its concentration does not noticeably change during the reaction.
Step 2: In the inversion of sucrose, sucrose is hydrolyzed to glucose and fructose in the presence of acid. The reaction is first order with respect to sucrose, with the acid effectively being in excess.
Step 3: This makes it a pseudo first order reaction as the concentration of water and acid do not limit the reaction rate.
Step 4: Therefore, the correct answer is the inversion of sucrose.