Evaluating False Statements on Cyclohexanol's Properties

  • Thread starter Thread starter a.a
  • Start date Start date
  • Tags Tags
    Properties
Click For Summary
SUMMARY

The discussion evaluates the properties of cyclohexanol, specifically its heat of vaporization and entropy values. The heat of vaporization is confirmed as 54 kJ/mol, with absolute entropies for liquid and gas being 200 J/K-mol and 328 J/K-mol, respectively. The false statement identified is that at 80°C, the free energy change for vaporization is negative, which was calculated incorrectly. The correct calculation shows that the free energy change (delta G) at this temperature is +8.797 kJ/mol, confirming statement c as false.

PREREQUISITES
  • Understanding of thermodynamic concepts such as heat of vaporization and entropy.
  • Familiarity with the Gibbs free energy equation: delta G = delta H - Tdelta S.
  • Basic knowledge of unit conversions, particularly between joules and kilojoules.
  • Experience with calculating thermodynamic properties at different temperatures.
NEXT STEPS
  • Study the implications of positive and negative Gibbs free energy in chemical reactions.
  • Learn about the relationship between entropy and spontaneity in phase changes.
  • Explore the calculation of heat capacities and their role in thermodynamic equations.
  • Investigate the properties of cyclohexanol and its applications in organic chemistry.
USEFUL FOR

Chemistry students, educators, and professionals involved in thermodynamics and physical chemistry, particularly those studying phase transitions and thermodynamic properties of organic compounds.

a.a
Messages
126
Reaction score
0

Homework Statement



Cyclohexanol has a heat of vaporization of 54 kJ/mol and the absolute entropies of the liquid and gas are 200 and 328 J/K-mol, respectively. Which of the following is false?


a. The entropy of vaporization is positive.

b. The heat of formation of liquid cyclohexanol is less than that of the vapour.

c. At 80oC the free energy change for the vaporization is negative.

d. At the boiling point the free energy change for vaporization is zero.

e. At 80oC, cyclohexanol vapour spontaneously condenses into a liquid.


Homework Equations



delta G = delta H - TdeltaS

The Attempt at a Solution



I know statements a, b, and d are true for all substances, so they are not false.

I calculated deltaG at 80degrees and got -45203146 KJ/mol, but that seems a little tp big. I can't figure out where I'm going wrong...

deltaG= 54 Kj/mol - (80 + 273.15 K)(128 J/Kmol)
= 54 KJ/mol- (353.15)(128000KJ/mol)
= -45203146 KJ/mol
 
Physics news on Phys.org
Oh, wow... I can't believe I made this mistake... hope it doesn't happen agian; exams are coming up.

I converted to KJ wrong, it should be 128J= 0.128KJ,
and that would make deltaG = + 8.797

So that means that statement c is false. :)
 

Similar threads

Chemistry A calculation of enthalpy, entropy, and Gibbs energy of vaporization
  • · Replies 1 ·
Replies
1
Views
2K
Entropy of Vaporization Calculation for 5 Moles of Argon at 87.5 K and 150 K
  • · Replies 1 ·
Replies
1
Views
2K
Chemistry homework help with enthelpy
  • · Replies 3 ·
Replies
3
Views
2K
How do I find the entropy variation?
  • · Replies 6 ·
Replies
6
Views
3K
Caculating normal boiling point using an equation of a line
  • · Replies 1 ·
Replies
1
Views
14K
How Much Heat is Needed to Convert Hydrazine from Solid to Gas?
  • · Replies 1 ·
Replies
1
Views
4K
Finding the final temperature of a final solution. putting ice in soda/water
  • · Replies 4 ·
Replies
4
Views
7K
Heat fusion, vaporization and entropy
  • · Replies 3 ·
Replies
3
Views
14K
Calculation of entropy change for melting ice
  • · Replies 1 ·
Replies
1
Views
5K
Estimate the standard enthelpy of formation
  • · Replies 9 ·
Replies
9
Views
13K