Question

Instantaneous rate of reaction for the reaction $3 A+2 B$ $\rightarrow 5 C$ is ______ .

• A. $+\frac{1}{3} \frac{d[A]}{d t}=-\frac{1}{2} \frac{d[B]}{d t}=+\frac{1}{5} \frac{d[C]}{d t}$
• B. $-\frac{1}{3} \frac{d[A]}{d t}=-\frac{1}{2} \frac{d[B]}{d t}=+\frac{1}{5} \frac{d[C]}{d t}$
• C. $-\frac{1}{3} \frac{d[A]}{d t}=+\frac{1}{2} \frac{d[B]}{d t}=-\frac{1}{5} \frac{d[C]}{d t}$
• D. $+\frac{1}{3} \frac{d[A]}{d t}=-\frac{1}{2} \frac{d[B]}{d t}=-\frac{1}{5} \frac{d[C]}{d t}$

Answer 1

Answer: (B)

Rate of disappearance of the reactant is equal to the rate of appearance of the product by relation shown below:
For example,
$aA + bB \rightarrow cC$
For this the Instantaneous rate of the reaction will be given as:
$-\frac{1}{ a } \frac{ d [ A ]}{ dt }=-\frac{1}{ b } \frac{ d [ B ]}{ dt }=+\frac{1}{ c } \frac{ d [ C ]}{ dt }$
Thus for the reaction: $3 A +2 B \rightarrow 5 C$ the instantaneous rate of the reaction will be given as:
$-\frac{1}{3} \frac{ d [ A ]}{ dt }=-\frac{1}{2} \frac{ d [ B ]}{ dt }=+\frac{1}{5} \frac{ d [ C ]}{ dt }$