JEE Main 2026 — Chemical Kinetics Question with Solution

For the reaction $A(g)\to B(g)+C(g)$, initially pressure of A is 1 bar.
Initially: total pressure = 1 bar.
After 100 min: total pressure = 1.5 bar.
Using initial and final pressures, if x bar of A decomposes, then A becomes (1-x), B = x, C = x.
Total pressure = 1-x+x+x = 1+x = 1.5, so x = 0.5 bar.
For a first-order reaction: $k=\frac{2.303}{t}\log \frac{[A{]}_0}{[A]}$.
Using pressures instead: $k=\frac{2.303}{100}\log \frac{1}{0.5}$
$=\frac{2.303}{100}\times \log 2=\frac{2.303\times 0.3}{100}=\frac{0.691}{100}$
$=6.91\times 10^{-3}$ min${}^{-1}$ ≈ $6.9\times 10^{-3}$ min${}^{-1}$