Question 1 through 4 all refer to the shelf life of a liquid vitamin c supplemen

Question

Question 1 through 4 all refer to the shelf life of a liquid vitamin c supplement at 25°c. For all these questions assume that liquid vitamin c supplement, which degrades with first order kinetics. It is inconvenient to measure degradation kinectic at common temperatures because degradation is too slow.
Using the method of initial rates, you determine that the rate constant of vitamin c degradation is 8.40x10^-4 min-1 at 60°c and 1.10x10^-3min-1 at 70°c.Calculate activation energy.
A.225cal/mol
B. 232 cal/mol
C.237cal/mol
D. 245cal/mol
calculate frequency factor
of vitamin c change.
A. 5.55x10^-3min-1
B. 5.43x10^-3 min-1
C.5.37 x10^-3 min-1
D. 5.29 x10^-3min-1
calculate rate constant of vitamin c at 25°c.
A. 5.87x10^-5 min-1
B. 5.98x10^-5 min-1
C. 6.13x10^-5min-1
D 6.25x10^-5 min-1
calculate shelf life at 25°c
A. 31.7 hr
B. 30.6 hr
C. 29.8 hr
D. 29.3 hr

Explanation / Answer

Activation energy is calculate dby using Arrhenius equation:

ln (K2/K1) = -Ea/R (1/T2 - 1/T1)

In the above questions, following valuses are given, K2= 8.40 X 10-4 , K1 = 1.10 X 10-3 , T2= 70o C= 333.15 K, T1 = 60o C= 343.15 K

R= Gas constant= 8.31J/ mol

ln (8.40 X 10-4) /  1.10 X 10-3 = -Ea / 8.31 (1/343.15- 1/333.15)

Solve for Ea. The correct answer is option D.

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