home > q&a board > chemistry > topic: time with first order reaction

Q BgQuestion:

Scholar
Karma Points: 200
Respect (51%):
posted by  b-ren on 9/9/2008 9:16:51 PM  |  status: Live  

Time with first order reaction

Course Textbook Chapter Problem
N/A N/A N/A N/A
Question Details:
Cyclopropane {\rm{(C}}_3 {\rm{H}}_6 ) reacts to form propene {\rm{(C}}_3 {\rm{H}}_6 ) in the gas phase. The reaction is first order in cylclopropane and has a rate constant of {5.87\; \times \;10^{ - 4} }/{\rm{s}} at 485 ^\circ {\rm C}.
 
 
If a 2.5 - reaction vessel initially contains 724 torr of cyclopropane at 485 ^\circ {\rm C}, how long will it take for the partial pressure of cylclopropane to drop to below 100 torr?
 
t=    min
Bonus Point Alert! Earn +4 additional karma points for helping this annual member.

AAnswers:

Answer Question
Sage
Karma Points: 4,684
posted by Jesley on 9/9/2008 10:39:04 PM  |  status: Live
Asker's Rating: Lifesaver   
b-ren's comment:
"Thanks alot"
Response Details:
initial concentration of cyclopropane(C3H6), [C3H6]0 = P/RT
                where, P = 724torr = 0.952629atm
                                              T = 4850C = 758.15K
                                      R = 0.08206atm.L/mol.K
 [C3H6]0  = ( 0.952629atm)/(0.08206atm.L/mol.K*758.15K)
                   =0.0153M
final pressure, P = 100torr=0.131579atm
the concentration at time (t), [C3H6]t = ( 0.131579atm)/(0.08206atm.L/mol.K*758.15K)
                                                                =2.115x10-3M
for first order reaction,
                ln ([C3H6]t / [C3H6]0) = -kt
t = -1/k* ln ([C3H6]t / [C3H6]0)
t =3371 sec
t =56.185min
Answer Question
Ask New Question

Join Cramster's Community

Cramster.com brings together students, educators and subject enthusiasts in an online study community. With around-the-clock expert help and a community of over 100,000 knowledgeable members, you can find the help you need, whenever you need it. Join for free today » How Cramster is different from tutoring »

Need Help In

Useful Links