Hint: It is not necessary to graph these data. (1) The observed half life for th

Question

Hint: It is not necessary to graph these data.

(1)
The observed half life for this reaction when the starting concentration is 0.520 M is ___s and when the starting concentration is 0.260 M is __s.

(2)
The average rate of disappearance of HI from t = 0 s to t = 521 s is ___ M s-1.

(3)
The average rate of disappearance of HI from t = 521 s to t = 781 s is ___ M s-1.

(4)
Based on these data, the rate constant for this _______zero/first/second order reaction is ___M s-1.

Explanation / Answer

Q1

if C = 0.52 M initially, then half vlaue is = 0.52/2 = 0.26 M, the time at which this happens ist = 521 s

therefore, half life = 521 s

then, when initial C is = 0.26 M, the hlf vslue = 0.26/2 = 0.13 M, the time is (781 -521) =260 s

Q2

Average rate, by definition, is given by

C/t = (Cfinal - Cinitial) /(tfinal - tinial) = (0.26-0.520)/(521-0) = -0.000499 M/s, or rate of reaction = 0.000499 M/s

Q3.

Average rate, by definition, is given by

C/t = (Cfinal - Cinitial) /(tfinal - tinial) = (0.13-0.26)/(260) = -0.0005 M/s, or rate of reaction = 0.0005 M/s

Q4.

the rate remains the SAME

the only case in which half life is constant is FIRST ORDER

so

t half = ln(2) / k

k = ln(2)/ (260 ) = 0.002665 1/s

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