A) 30 minutes
B) 40 minutes
C) 50 minutes
D) 38 minutes
Correct Answer: B
Solution :
In first phase, \[K=\frac{2.303}{20}\log \,\frac{90}{100}\] ?. (i) In second phase, \[K=\frac{2.303}{t}\,\log \,\frac{81}{100}\] ? (ii) From eq. (i) \[\frac{2.303}{20}\,\log \,\frac{90}{100}\,=\,\,\frac{2.303}{t}\,\log \,\,\frac{81}{100}\] \[t=\frac{20\left( log\,81-log\,100 \right)}{(log\,\,90-\log \,\,100)}\] \[=\frac{20(1.908-2)}{(1.954-2)}=\frac{20\times (-0.092)}{(-0.046)}\,\,=\,\,40\,\,\min \]You need to login to perform this action.
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