Question

Thermal decomposition of compound x is a first order reaction. If 75% of x is decomposed in 100 min. How long will it take for 90% of the compound to decompose?

Given log 2 = 0.30

• A. 190 min
• B. 176.66 min
• C. 166.66 min
• D. 156.66 min

Answer 1

Answer: (C)

166.66 min

Answer 2

K = $\frac{1}{t}$ ln $\left\lbrack \frac{1}{1 - 3/4} \right\rbrack$ = $\frac{1}{100}$ ln (4)

K = $\frac{\mathcal{l}n4}{100}$ and t.₉ = $\frac{1}{k}$ ln [10] = $\frac{100}{\mathcal{l}n4}$ ln 10

= $\frac{100}{.6}$ = 166.66 min