Question
First order gas phase reaction A B + C p_i = initial pressure of gas A, p_t = total pressure of the reaction mixture at time t Expression of rate constant (k) is
JEE Main
Chemistry
Chemical Kinetics
2026
JEE Main 2026 (05 April Shift 1)
JEE Main Chemistry Question (2026) — Solution
Options
- A. 1 t p_i 2p_i - p_t
- B. 1 t 2p_i p_i - p_t
- C. 1 t p_i 3p_i - 2p_t
- D. 1 t 3p_i 4p_i - p_t
Answer
A. 1 t p_i 2p_i - p_t
Step-by-step solution
The given reaction is A(g) B(g) + C(g) At t = 0, the initial pressure of A is p_i and the pressures of B and C are 0. At time t, let the decrease in pressure of A be x. Pressure of A = p_i - x Pressure of B = x Pressure of C = x Total pressure at time t is p_t = (p_i - x) + x + x = p_i + x From this, we get x = p_t - p_i The partial pressure of A at time t is P_A = p_i - x = p_i - (p_t - p_i) = 2p_i - p_t For a first order reaction, the rate constant k is given by k = 1 t P_ A,0 P_A Substituting the values, we get k = 1 t p_i 2p_i - p_t Answer: 1 t p_i 2p_i - p_t
Related: Chemistry — Chemical Kinetics · All PYQ Banks