Question

For gaseous reactions, the rate is often expressed in terms of $d P / dt$ instead of $dC / dt$ or $dn / d t$ (where $C$ is concentration and $n$ is the number of mole). What is the relation among these three expressions?

• A. $\frac{d C}{d t}=\frac{1}{V}\left(\frac{d n}{d t}\right)=\frac{1}{R T}\left(\frac{d P}{d t}\right)$
• B. $\frac{d C}{d t}=\left(\frac{d n}{d t}\right)=\left(\frac{d P}{d t}\right)$
• C. $\frac{d C}{d t}=\left(\frac{d n}{d t}\right)=\frac{1}{R T}\left(\frac{d P}{d t}\right)$
• D. $\frac{d C}{d t}=\frac{V}{R T}\left(\frac{d n}{d t}\right)$

Answer 1

Answer: (A)

$ C=\frac{n}{V}=\frac{P}{R T}$

$ \therefore \frac{d C}{d t}=\frac{1}{V}\left(\frac{d n}{d t}\right)=\frac{1}{R T}\left(\frac{dP}{d t}\right)$