270) For a given reaction of first order, it takes 15 minutes for the concentration to drop from 0.8 M litre⁻¹ to 0.4 M litre¹. The time required for the concentration to drop from 0.1 M litre⁻¹ to 0.025 M litre⁻¹ will be:

271) If for a certain first−order reaction, the initial rate is 0.65% min⁻¹, the half life in one hour is:

272) The rate constants k₁ and k₂ for two different reactions are 10^{16e−2000⁄T and 1015e−1000⁄T respectively. The temperature at which ₁ = k₂ is:}

273) When ethyl acetate was hydrolysed in presence of 0.1 N HCl, the rate constant was found to be 5.40 x 10⁻⁵ sec⁻¹. But when 0.1 N H₂SO₄ was used for hydrolysis, the rate constant was found to be 6.25 x 10⁻⁵sec⁻¹. Thus it may conclude that:

274) The rate constant for a second order reaction is 8 x 10⁻⁵M⁻¹sec⁻¹. How long will it take for a 1M solution to be reduced to 0.5M?