Question

The reaction $A\left(g\right)+2B\left(g\right)\to C\left(g\right)+D\left(g\right)$ is an elementary process. In an experiment in volving this reaction. The initial pressure of A and B are $P_A=0.6$ atm $P_B=0.8$atm respectively when $P_C=0.2$ atm, the rate of reaction relative to the initial rate is:

• A. $\frac{1}{6}$
• B. $\frac{1}{12}$
• C. $\frac{1}{36}$
• D. $\frac{1}{18}$

Answer 1

Answer: (A)

$\frac{1}{6}$

$A\left(g\right)+2\left(B\right)\to C\left(g\right)+D\left(g\right)$

t = 0 0.6 0.8 0 0

at t 0.6-x 0.8-x x x

since this the elementary reaction

rate,r = $K\left[B{]}^2\right[A]$

now $r_i=k\left(0.6\right)(0.8{)}^2=0.38K$

when $P_i=x-0.2$ atm

when $P_A=0.6-x=0.4$ atm

when $P_B=0.8-2x=0.4$ atm

$r_f=K\left(0.4\right)(0.4{)}^2=0.064K$

$r_1/r_2=0.064/0.384=1/6$