Physical Chem Notes-Practice 20

Physical Chem Notes-Practice 20 - E) Consider the mechanism...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Additional Kinetics Questions to Prepare You for Problem Set #3 A) Calculate the pseudo-first order rate constants for loss of F (assume [CH 4 ] and [H 2 O] are constant) in the two following reactions at 298 K, assuming v 1 = k[F][CH 4 ] and v 2 = k[F][H 2 O]. F + CH 4 HF + CH 3 k 1 = 1.6 × 10 –10 e -0.5 kcal/mole / RT cm 3 /(molecules sec) F + H 2 O HF + OH k 2 = 1.4 × 10 –10 cm 3 /(molecules sec) [ C H 4 ] = 5.0 x 10 13 molecules/cm 3 [ H 2 O] = 5.0 x 10 17 molecules/cm 3 B) What is the lifetime of F in reaction (1) in Question A ? In reaction (2)? C) Use the pseudo-first approximation to determine the time at which reaction (1) has decreased [F] by a factor of 100 from its original concentration in Question A . D) Rewrite the expression for the temperature dependence of k
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: E) Consider the mechanism below at 350 K and the constant concentrations of F, CH 4 , and O 2 . F + CH 4 HF + CH 3 k 1 = 1.6 10 10 e-0.5 kcal/mole / RT cm 3 /(molecules sec) CH 3 + O 2 CH 3 O 2 k 2 = 2 10 12 cm 3 /(molecules sec) [CH 4 ] = 5.0 10 13 molecules/cm 3 [F] = 2.0 10 10 molecules/cm 3 [O 2 ] = 5.0 10 17 molecules/cm 3 What is the steady state concentration of CH 3 ? Answers A) k' = k[CH4] For CH 4 , 3.4 10 3 sec-1 For H 2 O, 8.4 10 7 sec-1 B) lifetime, , = 1/k' For CH 4 , 2.9 10-4 sec For H 2 O, 1.2 10-8 sec C) ln([F] / [F] o ) = -k' t Solve for t =1.35 10-3 sec D) Ea/R = (500 cal/mole) / (1.987 cal /mole K) = 250 K k 1 = 1.6 10 10 e-250/T cm 3 /(molecules sec) E) 9.0 10 7 molecules / cm 3 20...
View Full Document

Ask a homework question - tutors are online