Exams › NEET › Chemistry

The rate constant of a first order reaction is 0.0693 min\( ^{-1} \) Time (in minutes) required for reducing an initial concentration of 20 mol \( l i t^{-1} \) to 2.5 mol \( l i t^{-1} \) is :

1. 40
2. 30
3. 20
4. 10

Correct answer: 30

Solution

For a first-order reaction, \(t=\frac{2.303}{k}\log\frac{C_0}{C_t}\). Since the concentration changes from 20 to 2.5, the ratio is 8, so the time comes out to 30 minutes. This matches the given rate constant exactly.

Related NEET Chemistry questions

• 18 g glucose \( \left(C_{6} H_{12} O_{6}\right) \) is added to \( 178.2 \mathrm{g} \) of water. The vapour pressure of this aqueous solution at \( 100^{0} C \) in torr is:
• Distribution law was given by:
• Assertion The specific charge of canal rays is not constant. Reason The mass of ion varies with speed.
• Which is the condition, unrelated to quantities, that indicates that the rate going into solution is equal to the rate coming out of solution?
• For the equilibrium, \( \boldsymbol{H}_{2} \boldsymbol{O}(\boldsymbol{s}) \Leftrightarrow \boldsymbol{H}_{2} \boldsymbol{O}(\boldsymbol{l}) \) which of the following is true?
• The freezing point of a solution containing 0.2 g of acetic acid in 20.0 g benzene is lowered by \( 0.45^{\circ} \mathrm{C} \). The degree of association of acetic acid in benzene is: [Assume acetic acid dimerizes in benzene and \( K_{f} \) for benzene \( =\mathbf{5 . 1 2} \mathbf{K} \) \( \left.\mathrm{kg} \mathrm{mol}^{-1}\right] \)

⚔️ Practice NEET Chemistry free + battle 1v1 →