1. The following data were collected at 20 °C for the reactio n below Acetone +
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Question
1. The following data were collected at 20 °C for the reactio n below Acetone + H+ + Br,-- + bromoacetone The ti time to uce a small but constant amount of bromoacetone was measured while varying the conce ntrations of Br Br, acetone, and H Br, (M) 0.010 0.010 0.020 0.020 acetone (M) 0.25 0.13 0.25 0.13 H (M) 0.10 0.10 0.10 0.40 Rate 35 18 36 71 What is the order of the reaction with respect to Br, acetone, an d H? z Zevo order Acefone Fiet ovder doubies Fist ovder doubles 2. For the reaction A + BC, which one of the following represents the correct graph s the correct graph of the present concentration of A with time? (Assume this reaction is a first-order reaction.)Explanation / Answer
1)
Let the rate expression be given as,
Rate = K [Br2]^a [Acetone]^b [H+]^c
From the given data
35 = K [0.01]^a [0.25]^b [0.1]^c ---------------- (1)
18 = K [0.01]^a [0.13]^b [0.1]^c ---------------- (2)
36 = K [0.02]^a [0.25]^b [0.1]^c ---------------- (3)
71 = K [0.02]^a [0.13]^b [0.4]^c ---------------- (4)
(1) / (2) gives,
35 / 18 = (25 / 13)^b
=> b = 1 (approx.)
(3) / (1) gives,
36 / 35 = (2)^a
=> a = 0 (approx.)
(4) / (1) gives,
71 / 18 = (2)^a x (4)^c
since a = 0
=> 71 / 18 = 4^c
=> c = 1 (approx.)
Therefore,
a = 0 , b = c = 1
Reaction is Zero Order with respect to Br2, 1st order with respect to acetone and 1st order with respect to H+
2)
For a first order reaction ,
[A(t)] = [A(t=0)] exp (-kt)
This is an exponential decay
=> Conc. of A is decreasing with time exponentially.
Hence the correct option would be graph (d)
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