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NEET-XII-Chemistry

04: Chemical Kinetics

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  • #2
    For the reaction:

    2A + B → A2B

    the rate = k[A][B]2 with k = 2.0 × 10-6 mol-2 L2 s-1. Calculate the initial rate of the reaction when [A] = 0.1 mol L-1, [B] = 0.2 mol L-1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L-1.
    Ans : The initial rate of the reaction is

    Rate = k [A][B]2

    = (2.0 × 10-6 mol-2 L2 s-1) (0.1 mol L-1) (0.2 mol L-1)2

    = 8.0 × 10-9 mol-2 L2 s-1

    When [A] is reduced from 0.1 mol L-1 to 0.06 mol-1, the concentration of A reacted = (0.1 - 0.06) mol L-1 = 0.04 mol L-1

    Therefore, concentration of B reacted = 0.02 mol L-1

    Then, concentration of B available, [B] = (0.2 - 0.02) mol L-1

    = 0.18 mol L-1

    After [A] is reduced to 0.06 mol L-1, the rate of the reaction is given by,

    Rate = k [A][B]2

    = (2.0 × 10-6 mol-2 L2 s-1) (0.06 mol L-1) (0.18 mol L-1)2

    = 3.89 mol L-1 s-1