Question

Consider the reaction, $2NO_2( g )\rightarrow 2NO(g) + O_2(g)$. In the figure below, identify the curves $X , Y$ and $Z$ associated with the three species in the reaction,

• A. $X = NO, Y = O_2, Z = NO_2$
• B. $X = O_2, Y - NO, Z = NO_2$
• C. $X = NO_2, Y = NO, Z = O_2$
• D. $X =O_2, Y = NO_2, Z =NO$

Answer 1

Answer: (A)

$2NO_{2}\left(g\right)\rightarrow2NO\left(g\right)+O_{2}\left(g\right)$
$r=-\frac{1}{2}\frac{d\left[NO_{2}\right]}{dt}$
$=+\frac{1}{2}\frac{d\left[NO\right]}{dt}=+\frac{d\left[O\right]}{dt}$
From the above rate equation, it is clear that rate of disappearance of $NO_2$ is equal to the rate of formation of $NO$.
Thus, the curve $X$ is associated with $NO$, $Y$ with $O_2$ and $Z$ with $NO_2$.