{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture 26 - e.g Find"H for CH4(g 2 O2(g CO2(g 2 H2O(l A...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
3/18/10 1 24 = [1 mol ! " H f ° (CO 2 ) + 2 mol ! " H f ° (H 2 O(l))] # [1 mol ! H f ° (CH 4 ) + 2 mol ! " H f ° (O 2 )] = [ # 393.5 kJ+2 mol ! ( # 285.6 kJ/mol)] # [ # 74.81kJ+2 mol ! (0)] e.g. Find " H° for : CH 4 (g) + 2 O 2 (g) ! CO 2 (g) + 2 H 2 O (l) A) + 889.9 kJ B) # 890.3 kJ C) + 890.3 kJ D) # 889.9 kJ E) # 604.3 kJ ! H o = n p ! H f o ( p ) " # n r ! H f o ( r ) # Products # Reactants = # 889.9 kJ combustion of methane is exothermic! Careful about phase Obtained using textbook data Use data sheet 25 4.2.C. Bond Dissociation Enthalpies (Section 9.4) E.g. C-H bonds: D (kJ/mol) Only ONE value Bond dissociation energy (D) is the energy required to break 1 mole of covalent bonds to form gaseous species (at 1 bar and the given reference temperature). i) Different types of bonds have different bond energies: See Table 9.2 ii) Same bonds in different molecules can also have different bond energies C # C : 347 kJ/mol C=C : 611 kJ/mol H-CBr 3 380 H-CCl 3 380 H-CF 3 430 H-CH 3 413 Bond sensitive to molecular environment average bond energy C # H : 414 kJ/mol Now use D to calculate bond dissociation enthalpies : ! H o = " n r D ( r ) # " n p D ( p ) " H rxn = D (bonds broken) - D (bonds formed)
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern