Question

In a first order reaction the $a/(a-x)$ was found to be $8$ after $10$ minute. The rate constant is:

• A. $(2.303\times 3log2)/10$
• B. $(2.303\times 2log3)/10$
• C. $10\times 2.303\times 2log3$
• D. $10\times 2.303\times 3log2$

Answer 1

Answer: (A)

$(2.303\times 3log2)/10$

For a first order reaction,

$k=\frac{1}{t}ln\frac{a}{a-x}$

$t=10min$

$(\frac{a}{a-x}=8)$

$k=\frac{2.303}{t}\log 8$ ($\because$ log 8=0.9 and log 2=0.3)

$=\frac{2.303\times 3}{t}\log 2$

$k=\frac{2.303\times 3}{10}\log 2$

Hence, the correct option is $A$