Can you help me with this A-chem question? (CH24) In gas chromatography, the dep

Question

Can you help me with this A-chem question? (CH24)

In gas chromatography, the dependence of the adjusted retention time, t_r' on temperature, T, is shown in the following equation, log t_r = a/T + b where a and b are constants for a specific compound on a specific column. When the column temperature is 400.6 K, a compound elutes at t_r' = 10.26 min. The same compound elutes from the column at t_r' = 24.72 min when the column temperature is decreased to 381.4 K. Calculate the constants a and b for this compound on this column. a = b = Predict the adjusted retention time for this compound on the same column at 362.5 K. t_r' =

Explanation / Answer

log t'r = a/T + b

Case 1

log 10.26 = a/400.6 + b ...............(1)

Case 2

log 24.72 = a/381.4 + b .................(2)

Substracting equatio 1 from 2

log 24.72 - log 10.26 = a (1/381.4 - 1/400.6)

1.3930 - 1.0111 = a (0.002622-0.002496)

0.3819 = a x 0.000126

a = 3030.95

From eq. 1

log 10.26 = a/400.6 + b

1.0111 = 3030.95/400.6 + b

1.0111 = 7.5660 + b

b = -6.5549 = -6.55

Case 3

log tr' = 3030.95/362.5 -6.55

log tr' = 3030.95/362.5 -6.55

log tr' = 1.8112

tr' = 64.74

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