Search found 10 matches

by Sylvia Li
Thu Jan 22, 2015 8:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 7.107 part b
Replies: 2
Views: 703

Re: Homework 7.107 part b

OH okay that makes perfect sense. I hadn't taken into account that the c-c bonds were not breaking. That helped a lot! Thank you, Daniel!
by Sylvia Li
Thu Jan 22, 2015 1:32 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 7.107 part b
Replies: 2
Views: 703

Homework 7.107 part b

The question asks: Consider the hydrogenation of benzene to cyclohexane, which takes place by the step-by-step addition of 2 H atoms per step. C6H6(l)+H2(g)->C6H8(l) C6H8(l)+H2(g)->C6H10(l) C6H10(l)+H2(g)->C6H12(l) The standard reaction enthalpies of each step are unknown (b) use bond enthalpies to ...
by Sylvia Li
Thu Jan 08, 2015 9:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 7.27, Gas constant temperature units
Replies: 9
Views: 1490

Re: Question 7.27, Gas constant temperature units

Oh, I see! Yes, I converted the change in temperature to Kelvin, not the initial and final values by themselves. I have the correct answer now. Thanks for your help!
by Sylvia Li
Thu Jan 08, 2015 4:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 7.27, Gas constant temperature units
Replies: 9
Views: 1490

Question 7.27, Gas constant temperature units

The question asks: Calculate the heat released by 5.025 g of Kr(g) at 0.400 atm as it cools from 97.6 degrees C to 25.0 degrees C at (a) constant pressure and (b) constant volume. Assume that krypton behaves as an ideal gas. I'm using the equations q=n*delta T*C(p,m) and C(p,m)=(5/2)*R. The only par...
by Sylvia Li
Sun Dec 14, 2014 12:48 am
Forum: Amphoteric Compounds
Topic: Fall 2009 final: #7B
Replies: 1
Views: 460

Fall 2009 final: #7B

The question asks "At what concentration of acetic acid does autoprotolysis of water need to be taken into account? Acetic acid, Ka=1.8 x 10^-5. Explain your answer and justify it with a calculation." The explanation is this: "When the concentration of H3O+ due to acetic acid is close...
by Sylvia Li
Sun Dec 14, 2014 12:34 am
Forum: *Indicators
Topic: Halfway point and stoichiometric point
Replies: 2
Views: 4939

Re: Halfway point and stoichiometric point

The halfway point to the stoichiometric point is also the point at which the weak acid or base acts at its optimum buffer capacity.
by Sylvia Li
Sun Dec 14, 2014 12:08 am
Forum: Naming
Topic: Oxalate as a bidentate
Replies: 3
Views: 943

Re: Oxalate as a bidentate

Just to add on, the formal charges of the other 2 oxygens(with the double bonds) are -2 each
by Sylvia Li
Sun Dec 14, 2014 12:05 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Tetrahedral vs. square planar
Replies: 2
Views: 1023

Re: Tetrahedral vs. square planar

Both square planar and tetrahedral molecules each have 4 bonded sites. However, square planars are basically octahedrals but with lone pairs of electrons in the axial position(AX4E2), whereas tetrahedral molecules have no lone pairs(AX4). For more on this refer to page 77 and 82 in the course reader.
by Sylvia Li
Sun Dec 14, 2014 12:00 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: NH2CH2CH2NH2
Replies: 3
Views: 986

Re: NH2CH2CH2NH2

Also, the lone pairs are conveniently spaced in such a way that both can form bonds with a central cation(the carbons act as "spacers"); in some cases, where there are too few or too many spacers placed in certain positions, even if the molecule has 2 lone pairs, they would form only one b...
by Sylvia Li
Sat Dec 13, 2014 11:53 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 2
Views: 403

Re: Coordination Number

The coordination number should be the number of bonds that are formed with the main cation; en, or ethylenediamine, has 2 nitrogens, each with a lone pair that can be donated. Since it's a polydentate, more specifically a bidentate, if it is (en)2, then the coordination number should be 4. As Gina1L...

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