JEE Main 2026 · 5 Apr · Shift 1 · Chemistry Q57

ChemistrySingle correct+4 / -1Question 57 of 75

First order gas phase reaction
$\ce{A -> B + C}$
$p_i$ = initial pressure of gas A, $p_t$ = total pressure of the reaction mixture at time $t$

Expression of rate constant ( $k$ ) is

\dfrac1t\ln\dfrac{p_i}{2p_i-p_t}

\dfrac1t\ln\dfrac{2p_i}{p_i-p_t}

\dfrac1t\ln\dfrac{p_i}{3p_i-2p_t}

\dfrac1t\ln\dfrac{3p_i}{4p_i-p_t}

Answer and worked solution

Official answer: A

Pressures. If A's pressure falls by x, B and C each rise by x:
$p_t=p_i+x,\qquad p_A=p_i-x=2p_i-p_t.$

First order.
$k=\frac1t\ln\frac{p_i}{2p_i-p_t}.$

(A)

Topics:Integrated rate equations

JEE Main 2026 · 5 Apr · Shift 1, Chemistry question 57