Logout Open In App
Open In App
Warning: foreach() argument must be of type array|object, bool given in /var/www/html/web/app/themes/studypress-core-theme/template-parts/header/mobile-offcanvas.php on line 20

Chapter 7: Q66E (page 400)

Question: Using the bond energies in Table \({\rm{7}}{\rm{.2}}\), determine the approximate enthalpy change for each of the following reactions:

(a) \({\rm{C}}{{\rm{l}}_{\rm{2}}}{\rm{(g) + 3}}{{\rm{F}}_{\rm{2}}}{\rm{(g)}} \to {\rm{2Cl}}{{\rm{F}}_{\rm{3}}}{\rm{(g)}}\)

(b) \({{\rm{H}}_{\rm{2}}}{\rm{C = C}}{{\rm{H}}_{\rm{2}}}{\rm{(g) + }}{{\rm{H}}_{\rm{2}}}{\rm{(g)}} \to {{\rm{H}}_{\rm{3}}}{\rm{CC}}{{\rm{H}}_{\rm{3}}}{\rm{(g)}}\)

(c) \({\rm{2}}{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}{\rm{(g) + 7}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {\rm{4C}}{{\rm{O}}_{\rm{2}}}{\rm{(g) + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O(g)}}\)

Short Answer

Expert verified

(a) For the reaction \({\rm{C}}{{\rm{l}}_{\rm{2}}}{\rm{(g) + 3}}{{\rm{F}}_{\rm{2}}}{\rm{(g)}} \to {\rm{2Cl}}{{\rm{F}}_{\rm{3}}}{\rm{(g)}}\), the value for enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 564\;kJ}}\).

(b) For the reaction \({{\rm{H}}_{\rm{2}}}{\rm{C = C}}{{\rm{H}}_{\rm{2}}}{\rm{(g) + }}{{\rm{H}}_{\rm{2}}}{\rm{(g)}} \to {{\rm{H}}_{\rm{3}}}{\rm{CC}}{{\rm{H}}_{\rm{3}}}{\rm{(g)}}\), the value for enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 128\;kJ}}\).

(c) For the reaction \({\rm{2}}{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{6}}}{\rm{(g) + 7}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {\rm{4C}}{{\rm{O}}_{\rm{2}}}{\rm{(g) + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O(g)}}\), the value for enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 2345\;kJ}}\).

Step by step solution

01

Concept Introduction

Bond energy is a measure of the bond strength in a chemical bond. The average value of bond-dissociation energy for all bonds of the same type in gas phase within the same chemical species gives the value of bond energy.

02

Enthalpy Change for first reaction

(a)

Bond Energy for\({\rm{Cl - Cl}}\)is:\({\rm{243 kJ/mol}}\)

Bond Energy for\({\rm{F - F}}\)is:\({\rm{160 kJ/mol}}\)

Bond Energy for \({\rm{Cl - F}}\) is: \({\rm{255 kJ/mol}}\)

Calculate the enthalpy change according to the reaction –

\(\begin{array}{c}{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = }}\sum {{{\rm{D}}_{{\rm{bonds broken }}}}} {\rm{ - }}\sum {{{\rm{D}}_{{\rm{bonds formed }}}}} \\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = 2}}{{\rm{D}}_{{\rm{Cl - Cl}}}}{\rm{ + 3}}{{\rm{D}}_{{\rm{F - F}}}}{\rm{ - 6}}{{\rm{D}}_{{\rm{Cl - F}}}}\\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = }}2(243) + 3(160) - 6(255) = {\rm{ - 564\;kJ}}\end{array}\)

Therefore, the enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 564\;kJ}}\).

03

 Step 3: Enthalpy Change for second reaction

(b)

Bond Energy for\({\rm{C = C}}\)is:\({\rm{611 kJ/mol}}\)

Bond Energy for\({\rm{C - H}}\)is:\({\rm{415 kJ/mol}}\)

Bond Energy for\({\rm{H - H}}\)is:\({\rm{436 kJ/mol}}\)

Bond Energy for\({\rm{C - C}}\)is:\({\rm{345 kJ/mol}}\)

Calculate the enthalpy change according to the reaction –

\(\begin{array}{l}{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = }}\sum {{{\rm{D}}_{{\rm{bonds broken }}}}} {\rm{ - }}\sum {{{\rm{D}}_{{\rm{bonds formed }}}}} \\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = }}{{\rm{D}}_{{\rm{C = C}}}}{\rm{ + 4}}{{\rm{D}}_{{\rm{C - H}}}}{\rm{ + }}{{\rm{D}}_{{\rm{H - H}}}}{\rm{ - }}{{\rm{D}}_{{\rm{C - C}}}}{\rm{ - 6}}{{\rm{D}}_{{\rm{C - H}}}}\\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = 611 + 4(415) + 436 - 345 - 6(415) = - 128\;kJ}}\end{array}\)

Therefore, the enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 128\;kJ}}\).

04

Enthalpy Change for third reaction

(c)

Bond Energy for\({\rm{C - C}}\)is:\({\rm{345 kJ/mol}}\)

Bond Energy for\({\rm{C - H}}\)is:\({\rm{415 kJ/mol}}\)

Bond Energy for\({\rm{O = O}}\)is:\({\rm{498 kJ/mol}}\)

Bond Energy for\({\rm{C = O}}\)is:\({\rm{741 kJ/mol}}\)

Bond Energy for\({\rm{O - H}}\)is:\({\rm{464 kJ/mol}}\)

Calculate the enthalpy change according to the reaction –

\(\begin{array}{l}{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = }}\sum {{{\rm{D}}_{{\rm{bonds broken }}}}} {\rm{ - }}\sum {{{\rm{D}}_{{\rm{bonds formed }}}}} \\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = 2}}{{\rm{D}}_{{\rm{C - C}}}}{\rm{ + 12}}{{\rm{D}}_{{\rm{C - H}}}}{\rm{ + 7}}{{\rm{D}}_{{\rm{O = O}}}}{\rm{ - 8}}{{\rm{D}}_{{\rm{C = O}}}}{\rm{ + 12}}{{\rm{D}}_{{\rm{O - H}}}}\\{\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = 2(345) + 12(415) + 7(498) - 8(741) - 12(464) = - 2345\;kJ}}\end{array}\)

Therefore, the enthalpy change is \({\rm{\Delta H}}_{{\rm{298}}}^{\rm{^\circ }}{\rm{ = - 2345\;kJ}}\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Write out the full electron configuration for each of the following atoms and for the monatomic ion found in binary ionic compounds containing the element: (a) \({\rm{Al}}\) (b) \({\rm{Br}}\) (c) \({\rm{Sr}}\) (d) \({\rm{Li}}\) (e) \({\rm{As}}\) (f) \({\rm{S}}\) .

Use the simulation (http://openstaxcollege.org/l/16MolecPolarity) to perform the following exercises for a two-atom molecule: (a) Adjust the electronegativity value so the bond dipole is pointing toward B. Then determine what the electronegativity values must be to switch the dipole so that it points toward A. (b) With a partial positive charge on A, turn on the electric field and describe what happens. (c) With a small partial negative charge on A, turn on the electric field and describe what happens. (d) Reset all, and then with a large partial negative charge on A, turn on the electric field and describe what happens.

The reaction of a metal, \({\rm{M}}\), with a halogen, \({{\rm{X}}_{\rm{2}}}\), proceeds by an exothermic reaction as indicated by this equation: \({\rm{M(s) + }}{{\rm{X}}_{\rm{2}}}{\rm{(g)}} \to {\rm{M}}{{\rm{X}}_{\rm{2}}}{\rm{(s)}}\). For each of the following, indicate which option will make the reaction more exothermic. Explain your answers.

(a) a large radius vs. a small radius for \({{\rm{M}}^{{\rm{ + 2}}}}\)

(b) a high ionization energy vs. a low ionization energy for \({\rm{M}}\)

(c) an increasing bond energy for the halogen

(d) a decreasing electron affinity for the halogen

(e) an increasing size of the anion formed by the halogen

For which of the following substances is the least energy required to convert one mole of the solid into separate ions?

(a) \({\rm{MgO}}\)

(b) \({\rm{SrO}}\)

(c) \({\rm{KF}}\)

(d) \({\rm{CsF}}\)

(e) \({\rm{Mg}}{{\rm{F}}_{\rm{2}}}\)

Write the Lewis structure for the diatomic molecule \({{\rm{P}}_{\rm{2}}}\), an unstable form of phosphorus found in high temperature phosphorus vapor.
See all solutions

Recommended explanations on Chemistry Textbooks

Physical Chemistry

Read Explanation

Inorganic Chemistry

Read Explanation

Organic Chemistry

Read Explanation

Kinetics

Read Explanation

Chemical Reactions

Read Explanation

Making Measurements

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free