Which mechanism is consistent with the facts given about the reaction rate equation-

mechanism (I)
mechanism (II)
both (I) and (II)
neither (I) nor (II)

Solution

Rate is determined by the slow step of the mechanism.

How could the progress of this reaction be best monitored?

by monitoring the colour of the reaction mixture
by titration of \(I_{3}^{-}\) with hypo
by precipitation of I^– with Ag⁺
by monitoring the change in pressure

Solution

\(I_{2} + 2S_{2}O_{3}^{-} \rightarrow 2I^{-} + S_{4}O_{6}^{2-}\)

DIRECTIONS: These are Assertion-Reason type questions.Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.

Statement-1 : According to steady state hypothesis, in a multi step reaction, the change in concentration with time for reactive intermediates is zero.
Statement-2 :The intermediates are so reactive that after a brief initial period their concentrations rise from zero to a small value and remains constant for most of the duration of the reaction

Statement-1 is True, Statement-2 is True,Statement-2 is a correct explanation for Statement -1
Statement-1 is True, Statement-2 is True ;Statement-2 is NOT a correct explanation for Statement - 1
Statement-1 is True, Statement-2 is False
Statement-1 is False, Statement-2 is True

DIRECTIONS: These are Assertion-Reason type questions.Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.

Statement-1 :If the activation energy of a reaction is zero,temperature will have no effect on the rate constant.
Statement-2 :Lower the activation energy, faster is thereaction.

Statement-1 is True, Statement-2 is True,Statement-2 is a correct explanation for Statement -1
Statement-1 is True, Statement-2 is True ;Statement-2 is NOT a correct explanation for Statement - 1
Statement-1 is True, Statement-2 is False
Statement-1 is False, Statement-2 is True

Solution

According to Arrhenius equation, k= Ae^{–E_a/ RT}
When E_a = 0, k = A

DIRECTIONS: These are Assertion-Reason type questions.Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.

Statement-1 :If in a zero order reaction, the concentration of the reactant is doubled. the half-life period is also doubled.
Statement-2 :For a zero order reaction,the rate of reaction is independent of initial concentration

Statement-1 is True, Statement-2 is True,Statement-2 is a correct explanation for Statement -1
Statement-1 is True, Statement-2 is True ;Statement-2 is NOT a correct explanation for Statement - 1
Statement-1 is True, Statement-2 is False
Statement-1 is False, Statement-2 is True

Solution

For a zero order reaction,t_1/2 = [A₀] / 2k

The rate of a reaction doubles when its temperature changes from 300 K to 310 K.Activation energy of such a reaction will be : (R = 8.314 J K–1 mol^-1 and log 2 = 0.301)

53.6 kJ mol^-1
48.6 kJ mol^-1
58.5 kJ mol^-1
60.5 kJ mol^-1

Solution

For a first order reaction (A)⟶ products the concentration of A changes from 0.1 M to 0.025 M in 40 minutes.The rate of reaction when the concentration of A is 0.01 M is:

1.73 × 10^-5 M/min
3.47 × 10^-4 M/min
3.47 × 10^-5 M/min
1.73 × 10^-4 M/min

Solution

The half life period of a first order chemical reaction is 6.93 minutes. The time required for the completion of 99% of the chemical reaction will be (log 2 =0.301)

23.03 minutes
46.06 minutes
460.6 minutes
230.03 minutes

Solution

Solution

Consider the reaction, 2A + B ⟶ products. When concentration of B alone was doubled, the half-life did not change. When the concentration of A alone was doubled,the rate increased by two times. The unit of rate constant for this reaction is

s^-1
L mol^-1 s^-1
no unit
mol L^-1 s^-1

Solution

Since doubling the concentration of B does not change half life, the reaction is of 1st order w.r.t. B.Order of reaction with respect to A = 1 because rate of reaction doubles when concentration of A is doubled keeping concentration of B constant.
∴ Order of reaction = 1 + 1 = 2 and units of second order reaction are L mol^-1 sec^-1

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