How Do You Calculate Entropy Changes in Thermodynamics?

AI Thread Summary
To calculate entropy changes for the cooling of 1 mol of O2 from 298 K to liquid state at 90.19 K, both reversible and irreversible processes need to be considered. The enthalpy change of vaporization is given as 6820 J/mol at 90.19 K, and the specific heat capacity for the gas is Cp = 7/2 R. The discussion emphasizes the importance of understanding the calculations for the system, surroundings, and universe in thermodynamics. There is a call for assistance due to the urgency of the homework deadline. Effective problem-solving requires a clear approach to these entropy calculations.
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Thermodynamics for P Chem NEEd HELP By tomorrow!

Homework Statement



What are the values of the entropy changes (system, surroundings, and universe) for the cooling of 1 mol of O2 (g) from 298 K to O2 (l) at 90.19 K if the process is done

a. Reversibly
b. Irreversibly

by placing the sample in liquid hydrogen at 13.96 K? Assume enthalpy change of vaporization is 6820 j/mol at 90.19 K and Cp = 7/2 R for the gas.

Homework Equations



How do you solve this problem for all types of entropy?(entropy changes (system, surroundings, and universe)


The Attempt at a Solution


Have no clue how to start it. Please help!
 
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Welcome. Please use this resource wisely. Posts that specify that you need help in the next 24 hours or shorter are probably not going to encourage many members to help you. If you let your problem get that urgent, the motivation to help you will be minimal.
 
Thread 'Confusion regarding a chemical kinetics problem'

Thread 'Confusion regarding a chemical kinetics problem'

TL;DR Summary: cannot find out error in solution proposed. [![question with rate laws][1]][1] Now the rate law for the reaction (i.e reaction rate) can be written as: $$ R= k[N_2O_5] $$ my main question is, WHAT is this reaction equal to? what I mean here is, whether $$k[N_2O_5]= -d[N_2O_5]/dt$$ or is it $$k[N_2O_5]= -1/2 \frac{d}{dt} [N_2O_5] $$ ? The latter seems to be more apt, as the reaction rate must be -1/2 (disappearance rate of N2O5), which adheres to the stoichiometry of the...
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