University of Wisconsin, W... a search saplinglearning.com 2478013 Resources 5/8

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University of Wisconsin, W... a search saplinglearning.com 2478013 Resources 5/8/2016 11:00 PM A 54.5/100 4/30/2016 05:27 PM Gradebook O Assignment Information Score Periodic Table Available From 4/20/2016 06:00 PM 00 Question 10 of 24 Incorrect correct 5/8/2016 11:00 PM Due Date: Map 00 Points Possible 00 00 Grade Category: Graded For a particular reaction, AHois 20.1 kJ and AS is 45.9 J/K. Assuming these values change very little with e, over wha e range is the reaction spontaneous in the forward direction? Description emperatu emperatu 00 Homework Policies: Numbe 00 O ess than The reaction is spontaneous for temperatures T- 39 You can check your answers. O greater than You can view solutions when you complete or give up on any question. You can keep trying to answer each question until you get it right or give up. 00 You lose 5% of the points available to each answer in your question for each incorrect attempt at that answer 00 O Help With This Topic 00 There is additional feedback Web Help & Videos available! 00 View this feedback by clicking on the bottom divider bar. Click on the divider Technical support and Bug Reports bar again to hide the additional feedback. Close Previous 3 Give Up & View Solution Try Again Next Exit Explanation 00

Explanation / Answer

Use the next equation to determine if a chemical reaction is spontaneous:

Gibbs free energy equation.
*deltaG = deltaH - T.deltaS

deltaG, gibbs free energy change.
deltaH, enthalpy change
deltaS, entropy change
T, temperature (K)

*a chemical reaction will be spontaneous if the gibbs free energy change is negative

Over what temperature range is the reaction spontaneous?

deltaH = 20100 J
deltaS = 45.9 J/K

Calculate temperature at which deltaG is zero.

Clear T:
0 = deltaH - T.deltaS
T = deltaH/deltaS
T = 20100 J/45.9 J/K
T = 437.91 K

If the temperature increases deltaG becomes negative, so:
The reaction is spontaneous for temperatures greater than 437.91 K.

For example, at 500 K:
deltaG = 20100 J - (500 K).(45.9 J/K)
deltaG = -2850 J
The reaction is spontaneous at 500 K.

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