Call Now to Set Up Tutoring:

(888) 888-0446

Physical Chemistry : Gibbs Free Energy

Study concepts, example questions & explanations for Physical Chemistry

Create An Account

All Physical Chemistry Resources

1 Diagnostic Test 87 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 : Thermochemistry And Thermodynamics

For Constant Temperature, Gibbs Free Energy is defined as:

$\Delta G = \Delta H - T \Delta S \,$

Where , $\small \Delta G$ is the change in Gibbs Free Energy, $\small \Delta H$ is the change in enthalpy, $\small T$ is temperature, and $\small \Delta S$ is the change in entropy.

Which of the following scenarios is not possible?

Possible Answers:

$\Delta H>0, \Delta S<0, \Delta G<0$

$\Delta H < 0 , \Delta S < 0, \Delta G < 0$

$\Delta H>0, \Delta S<0, \Delta G>0$

$\Delta H>0, \Delta S>0, \Delta G>0$

$\Delta H >0, \Delta S>0, \Delta G<0$

Correct answer:

$\Delta H>0, \Delta S<0, \Delta G<0$

Explanation:

The following condition is not possible:

$\Delta H > 0 ,\Delta S < 0, \Delta G < 0$

This is because if enthalpy is positive, and entropy is negative, the negative sign in front of the temperature term in the formula becomes positive. Addition of 2 positive numbers can not be negative. Plugging in arbitrary numbers into the other conditions can show they are all possible.

Take the following condition:

$\Delta H>0, \Delta S>0$

Then Gibbs free energy $(\Delta G)$ can either be positive or negative, depending on the magnitude of enthalpy, entropy, and temperature. (If enthalpy is much larger than entropy and temperature, then the difference will be positive, but if entropy * is greater than the enthalpy, then the difference will be negative).

Report an Error

Example Question #1 : Gibbs Free Energy

For constant temperature, Gibbs free energy is defined as:

$\Delta G = \Delta H - T \Delta S \,$

Where , $\small \Delta G$ is the change in Gibbs free energy, $\small \Delta H$ is the change in enthalpy, $\small T$ is temperature, and $\small \Delta S$ is the change in entropy.

Given that a system is spontaneous, which of the following states are possible?

I. $\Delta G<0, \Delta S>0, \Delta H<0$

II. $\Delta G<0, \Delta S<0, \Delta H>0$

III. $\Delta G<0, \Delta S>0, \Delta H>0$

IV. $\Delta G>0, \Delta S<0, \Delta H>0$

Possible Answers:

I and III

IV only

I, II, and III

II and III

I, II, III, and IV

Correct answer:

I and III

Explanation:

Condition I is always true. Condition II is never true, as Gibbs free energy cannot be negative if enthalpy is positive and entropy is negative. Condition III may be true if temperature is very high (this is the scenario when the $T*\Delta S$ term dominates the $\Delta H$ term. Condition IV is not possible because $\Delta G>0$ and we were given a system with a Gibbs free Energy that is $\Delta G<0$ (we were told the system was spontaneous).

Report an Error

Example Question #1 : Thermochemistry And Thermodynamics

The enthalpy of a reaction is $35\frac{kJ}{mol}$ and the entropy of a reaction is $3\frac{J}{mol\cdot K}$ . Which of the following is the Gibbs free energy (in $\frac{kJ}{mol}$ ) of this reaction?

Possible Answers:

Cannot be determined from the given information

$32\frac{kJ}{mol}$

$72\frac{kJ}{mol}$

$34.9\frac{kJ}{mol}$

Correct answer:

Cannot be determined from the given information

Explanation:

Gibbs free energy of a system can be solved using the following equation.

$\bigtriangleup G = \bigtriangleup H + T\bigtriangleup S$

where $\bigtriangleup G$ is change in Gibbs free energy, $\bigtriangleup H$ is change in enthalpy, is temperature in Kelvins and $\bigtriangleup S$ is change in entropy. To solve for $\bigtriangleup G$ we need all three of the variables. We are not given the temperature; therefore, we cannot solve for Gibbs free energy.

Report an Error

Example Question #1 : Gibbs Free Energy

In an exergonic reaction, products will have __________ Gibbs free energy and the reaction is __________.

Possible Answers:

lower . . . spontaneous

higher . . . spontaneous

lower . . . nonspontaneous

higher . . . nonspontaneous

Correct answer:

lower . . . spontaneous

Explanation:

Exergonic reaction suggests that the Gibbs free energy is negative. Since the change in Gibbs free energy is defined as Gibbs free energy of products - Gibbs free energy of reactants, a negative change in Gibbs free energy suggests that the products have a lower Gibbs free energy than reactants. A reaction is spontaneous if it has negative Gibbs free energy; therefore, exergonic reactions are always spontaneous. This is because the reaction is producing a more stable product (lower energy) from a less stable reactant (higher energy).

Report an Error

View Physical Chemistry Tutors

Wendie
Certified Tutor

East Tennessee State University, Bachelor of Science, Kinesiotherapy.

View Physical Chemistry Tutors

Ekta
Certified Tutor

Punjab Agricultural University, India, Doctorate (PhD), Chemistry.

View Physical Chemistry Tutors

Gregory
Certified Tutor

Pennsylvania State University-Main Campus, Bachelor of Science, Chemical Engineering. Carnegie Mellon University, Doctor of P...

All Physical Chemistry Resources

1 Diagnostic Test 87 Practice Tests Question of the Day Flashcards Learn by Concept

Physical Chemistry Tutors in Top Cities:

Popular Courses & Classes

GMAT Courses & Classes in San Diego, Spanish Courses & Classes in San Francisco-Bay Area, SAT Courses & Classes in Dallas Fort Worth, ISEE Courses & Classes in Seattle, ISEE Courses & Classes in Houston, ISEE Courses & Classes in Washington DC, ISEE Courses & Classes in Boston, Spanish Courses & Classes in Houston, Spanish Courses & Classes in Dallas Fort Worth, GMAT Courses & Classes in Denver

Popular Test Prep

SSAT Test Prep in Boston, ISEE Test Prep in Denver, GRE Test Prep in Seattle, MCAT Test Prep in Chicago, GRE Test Prep in Philadelphia, LSAT Test Prep in Chicago, SSAT Test Prep in San Francisco-Bay Area, LSAT Test Prep in San Francisco-Bay Area, GMAT Test Prep in Denver, SAT Test Prep in Dallas Fort Worth

DMCA Complaint

If you believe that content available by means of the Website (as defined in our Terms of Service) infringes one or more of your copyrights, please notify us by providing a written notice (“Infringement Notice”) containing the information described below to the designated agent listed below. If Varsity Tutors takes action in response to an Infringement Notice, it will make a good faith attempt to contact the party that made such content available by means of the most recent email address, if any, provided by such party to Varsity Tutors.

Your Infringement Notice may be forwarded to the party that made the content available or to third parties such as ChillingEffects.org.

Please be advised that you will be liable for damages (including costs and attorneys’ fees) if you materially misrepresent that a product or activity is infringing your copyrights. Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney.

Please follow these steps to file a notice:

You must include the following:

A physical or electronic signature of the copyright owner or a person authorized to act on their behalf; An identification of the copyright claimed to have been infringed; A description of the nature and exact location of the content that you claim to infringe your copyright, in \ sufficient detail to permit Varsity Tutors to find and positively identify that content; for example we require a link to the specific question (not just the name of the question) that contains the content and a description of which specific portion of the question – an image, a link, the text, etc – your complaint refers to; Your name, address, telephone number and email address; and A statement by you: (a) that you believe in good faith that the use of the content that you claim to infringe your copyright is not authorized by law, or by the copyright owner or such owner’s agent; (b) that all of the information contained in your Infringement Notice is accurate, and (c) under penalty of perjury, that you are either the copyright owner or a person authorized to act on their behalf.

Send your complaint to our designated agent at:

Charles Cohn Varsity Tutors LLC
101 S. Hanley Rd, Suite 300
St. Louis, MO 63105

Or fill out the form below:

Do not fill in this field

Contact Information

* Full legal name

Company name

* Phone number

* Email address

Address

* Address1

Address2

* City

* State

* Zipcode

* Country

Complaint Details

* URL of copyrighted work (where your original material is located)

* Please describe the copyrighted work so that it may be easily identified

I am the owner, or an agent authorized to act on behalf of the owner of an exclusive right that is allegedly infringed.

I have a good faith belief that the use of the material in the manner complained of is not authorized by the copyright owner, its agent, or the law.

This notification is accurate.

I acknowledge that there may be adverse legal consequences for making false or bad faith allegations of copyright infringement by using this process.

* Signature (your digital signature is legally binding)

HIGH SCHOOL

GRADUATE SCHOOL

K-8

Search 50+ Tests

math tutoring

science tutoring

foreign languages

elementary tutoring

other

Search 350+ Subjects

Physical Chemistry : Gibbs Free Energy

Study concepts, example questions & explanations for Physical Chemistry

All Physical Chemistry Resources

Example Questions

Example Question #1 : Thermochemistry And Thermodynamics

Example Question #1 : Gibbs Free Energy

Example Question #1 : Thermochemistry And Thermodynamics

Example Question #1 : Gibbs Free Energy

All Physical Chemistry Resources

Report an issue with this question

DMCA Complaint

Contact Information

Address

Complaint Details

Email address:
Your name:
Feedback: