Answer :
The correct expression for rate of reaction is:
[tex]Rate=-\frac{d[A]}{dt}=-\frac{1}{2}\frac{d[B]}{dt}=+\frac{d[C]}{dt}[/tex]
The [A] decreasing at 0.14 mol/L.s
Explanation :
The given rate of reaction is,
[tex]A(g)+2B(g)\rightarrow C(g)[/tex]
The expression for rate of reaction :
[tex]\text{Rate of disappearance of A}=-\frac{d[A]}{dt}[/tex]
[tex]\text{Rate of disappearance of B}=-\frac{1}{2}\frac{d[B]}{dt}[/tex]
[tex]\text{Rate of formation of C}=+\frac{d[C]}{dt}[/tex]
So,
[tex]Rate=-\frac{d[A]}{dt}=-\frac{1}{2}\frac{d[B]}{dt}=+\frac{d[C]}{dt}[/tex]
Now we have to calculate how fast is [A] decreasing.
Given:
[tex]-\frac{d[B]}{dt}=0.28mol/L.s[/tex]
[tex]-\frac{1}{2}\frac{d[B]}{dt}=-\frac{1}{2}\times 0.28mol/L.s=-0.14mol/L.s[/tex]
[tex]-\frac{d[A]}{dt}=-\frac{1}{2}\frac{d[B]}{dt}=-0.14mol/L.s[/tex]
Hence, the [A] decreasing at 0.14 mol/L.s