Chemical Kinetics

For a reversible reaction R P, at constant temperature, both the forward and the backward reactions are first order elementary reactions with rate constants kf and kb, respectively. At time zero, the concentration of R is [R]0 and the concentration of P is zero. At any given time, [R] and [P] are the concentrations of R and P, respectively. If kb = 4kf, the correct graphical representation of the reaction is

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For a first-order reaction R P at a given temperature, k is the rate constant. For this reaction, at the given temperature, the concentrations of R and P at a time t are [R] and [P], respectively. The correct graphical representation(s) for this reaction is(are)

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Consider a reaction A + R Product. The rate of this reaction is measured to be k[A][R]. At the start of the reaction, the concentration of R, [R]0, is 10-times the concentration of A, [A]0. The reaction can be considered to be a pseudo first order reaction with assumption that k[R] = k' is constant. Due to this assumption, the relative error (in %) in the rate when this reaction is 40 % complete, is . [k and k' represent corresponding rate constants]

Consider the following reaction, 2H2(g) + 2NO(g) N2(g) + 2H2O(g) which follows the mechanism given below: 2NO(g) k-1 k1 N2O2(g) (fast equlibrium) N2O2(g) + H2(g) k2 N2O(g) + H2O(g) (slow reaction) N2O(g) + H2(g) k3 N2(g) + H2O(g) (fast reaction) The order of the reaction is .

A sample initially contains only U-238 isotope of uranium. With time, some of the U-238 radioactively decays into Pb-206 while the rest of it remains undisintegrated. When the age of the sample is P 108 years, the ratio of mass of Pb-206 to that of U-238 in the sample is found to be 7. The value of P is . [Given: Half-life of U-238 is 4.5 109 years; e 2 = 0.693]