Question

8.
The gaseous reaction A (g) → 2B (g) + C 19
obeys first order kinetics. If the initial p = 90
and pressure after 10 minutes = 180 mm.
velocity constant k of the reaction is
​

Answer 1

The gaseous reaction, A(g) → 2B(g) + C(g) obeys first order kinetics.

initial pressure, Pi = 90 mm

after 10 minutes,

pressure of A = P - x

pressure of B = 2x

pressure of C = x

so, total pressure after 10 minutes , Pt = P -x + 2x + x = P + 2x = 90 + 2x

but given, pressure after 10 minutes = 180mm

so, 90 + 2x = 180

or, 2x = 90 => x = 45mm

so, Final pressure , Pf = P - x = 90mm - 45mm = 45mm

now applying first order reaction formula,

k = 2.303/t log[Pi/Pf]

= 2.303/(10 × 60) log[90/45]

= 2.303/(600) × log2

= 2.303 × log2/600

= 0.00115 sec^-1

= 1.15 × 10^-3 sec^-1

hence, rate constant of reaction is 1.15 × 10^-3 sec^-1