Practicing Success
\(t_{99.9\%}\) with respect to \(t_{90\%}\) for a first order reaction is: |
Two One Three Four |
Three |
The correct answer is option 3. Three. We know, for a first order reaction \(t = \frac{2.303}{k}log \frac{a}{a - x}\, \ -------(i)\) For \(t_{99.9\%}\) Let, \(a =100\) and \(x = 99.9\) \(∴ a - x = 100- 99.9 = 0.1\) Therefore, equation (i) becomes \(t_{99.9\%} = \frac{2.303}{k}log \frac{100}{0.1}\) or, \(t_{99.9\%} = \frac{2.303}{k}log (1000)\) or, \(t_{99.9\%} = \frac{2.303}{k} × 3\, \ ------(ii)\) For \(t_{90\%}\) Let, \(a =100\) and \(x = 90\) \(∴ a - x = 100- 90 = 10\) Therefore, equation (i) becomes \(t_{90\%} = \frac{2.303}{k}log \frac{100}{10}\) or, \(t_{90\%} = \frac{2.303}{k}log (10)\) or, \(t_{90\%} = \frac{2.303}{k} × 1\, \ ------(iii)\) Dividing equation (ii) by equation (iii) \(\frac{t_{99.9\%}}{t_{90\%}} = \frac{\frac{2.303}{k} × 3}{\frac{2.303}{k} × 1}\) or, \(\frac{t_{99.9\%}}{t_{90\%}} = \frac{3}{1}\) or, \(t_{99.9\%} = 3 t_{90\%}\) |