14.6.2) Hint: It is not necessary to graph these data. (1) The observed half lif

Question

14.6.2)

Hint: It is not necessary to graph these data.

(1)
The observed half life for this reaction when the starting concentration is 4.47×10-3 M is s and when the starting concentration is 2.24×10-3 M is...?....s.

(2)
The average rate of disappearance of NH3 from t = 0 s to t = 998 s is....?.....M s-1.

(3)
The average rate of disappearance of NH3 from t = 998 s to t = 1.50×103 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

The data given suggests the concentration is droppong to 50% of the previous value for each run.

hence half life for 1st to 2nd change is 998 sec,

the rate for the 1st two data points (-rA)= (-2.24*10-3 + 4.47*10-3)/998=2.23*10-6 M/sec

for the second and third point, -rA= (-1.12+2.24)*10-3/(1500-998)=2.23*10-6 M/sec

for the third and 4th data pointm -rA= (1.12*10-3-5.56*10-4)/(1750-1500)= 2.23*10-6 M/sec

Rate is constant and is independent of concentrations. so this is the case for zero order reaction for which the rate

-rNH3= K[NH3]0, O is the order of NH3 in the reaction. So the rate constant, K= 2.23*10-6 M/sec

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