Question

The decomposition of N2O5 in chloroform was followed by measuring the volume of O2 gas evolved: 2N2O5 (CCI4) $\rightarrow$ 2N2O4 (CCI4) + O2 (g). The maximum volume of O2 gas obtained was 100cm3. In 500 minutes, 90 cm3 of O2 were evolved. The first order rate constant (in min–1) for the disappearance of N2O5 is :

• A. $\frac{2.303}{500}$
• B. $\frac{2.303}{500}\log\frac{100}{90}$
• C. $\frac{2.303}{500}\log\frac{100}{90}$
• D. $\frac{100}{10 \times 500}$

Answer 1

Answer: (A)

$\frac{2.303}{500}$

Answer 2

$kt = In\left( \frac{C_{O}}{C_{t}} \right)$

}{\text{t=t} \text{20 c}\text{m}^{3} \text{180c}\text{m}^{3}\ \text{90 c}\text{m}^{3}\ }$$$\text{t=} \text{0 } \text{200c}\text{m}^{3}\ \text{100 c}\text{m}^{3}\ $Initial volume of $N_{2}O_{5}\text{ = 200 c}\text{m}^{3}.$ because Max. volume of $O_{2}\text{ = 100 c}\text{m}^{3}.$ $\therefore K \times 500 = In\left( \frac{200}{20} \right) \Rightarrow k = \frac{In10}{500} = \frac{2.303}{500}$.