JEE Main 2026 · 23 January · morning · Numerical answer · +4 / −1
For the thermal decomposition of reactant AB(g), the following plot is constructed.
The half life of the reaction is ' x^' min.
x= ____ min. (Nearest integer)
Answer and solution
Answer 10
Solution
Chemistry ma’am · 3 steps
A straight line on a [AB] versus time plot means zero order, so read k as the slope.
- Spot the order. The concentration falls in a straight line with time. That is the signature of a zero-order reaction, where [AB] = [AB]₀ - kt.
- Read k from slope. The intercept gives [AB]₀ = 0.6 M. The concentration drops from 0.6 M to 0.5 M in 200 s, so k = 0.1/200 = 5 × 10⁻⁴ M s⁻¹.
t_(1/2) = [AB]₀/2k = 0.6/(2 × 5 × 10⁻⁴) = 600 s
- So. The question asks for minutes: 600 s = 10 min, so x = 10.
The common slip: 600. Leaving the half-life in seconds gives 600, but the blank asks for minutes, so divide by 60.
The idea to keep. Linear [A] versus t means zero order: the slope is -k and t_(1/2) = [A]₀/2k, so the half-life depends on the starting concentration. Always check the time unit asked.
Answer from the NTA final answer key. Solution by PrepWiser.