Search found 12 matches

by Maria Davila 2I
Tue Jan 27, 2015 12:04 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Quiz 1 Winter 2014 #3
Replies: 2
Views: 470

Re: Quiz 1 Winter 2014 #3

Add all bond enthalpies. Remember that when you are breaking bonds you need to use energy to break the bonds, therefore bond enthalpy is positive but when you are forming the bonds , those bond enthalpies will be negative because you are releasing. Then you add the positives (from the bonds broken) ...
by Maria Davila 2I
Mon Jan 26, 2015 11:55 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy with Constant Volume
Replies: 4
Views: 580

Re: Internal Energy with Constant Volume

Thanks so much Niharika, you have been a great help in many of these posts!
by Maria Davila 2I
Mon Jan 26, 2015 11:09 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy with Constant Volume
Replies: 4
Views: 580

Internal Energy with Constant Volume

For Quiz 1 Prep Winter 2014, question 2 seems tricky in the sense that


where volume is constant and since
with v=0, then w=0 .

So in the end you will have


which is +2.50kJ.

Is this the correct thought process behind this?
by Maria Davila 2I
Mon Jan 26, 2015 10:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Problem 7.31- Energy Per Photon & Amount of Energy Needed to
Replies: 4
Views: 10041

Re: Problem 7.31- Energy Per Photon & Amount of Energy Neede

When you are finding the energy of a photon you make use of two equations: c=\lambda *v and E_p_h_o_t_o_n = hv you then substitute v (in the second equation) for \frac{c}{\lambda } which another way of writing equation 1. Now you can use the wavelength which you will have to turn into meters to canc...
by Maria Davila 2I
Mon Jan 26, 2015 10:11 pm
Forum: Calculating Work of Expansion
Topic: When to use reversible or irreversible work?
Replies: 2
Views: 396

Re: When to use reversible or irreversible work?

If not clearly stated that it is irreversible do we assume work is reversible?
by Maria Davila 2I
Mon Jan 26, 2015 10:08 pm
Forum: Calculating Work of Expansion
Topic: How much work water do when it freezes?
Replies: 7
Views: 2818

Re: How much work water do when it freezes?

I tried this problem and I get the same thing Tiffany is getting when rounded off until the end. -0.94. I used all the numbers and rounded off in the end. Either way thanks Kita for splitting this into clear steps, easy to follow.
by Maria Davila 2I
Mon Jan 26, 2015 8:53 pm
Forum: Calculating Work of Expansion
Topic: Quiz 1 preparation, winter 2013 #3
Replies: 5
Views: 783

Re: Quiz 1 preparation, winter 2013 #3

Definitely looking at your graph helps just like Niharika mentioned. By looking at the paths taken you can see when Pressure is constant in each pathway. The equation for work is -P(Delta V) , so you need Pressure when it is constant, in pathway 1 it is at 5atm, so you would use the Volume change wh...
by Maria Davila 2I
Sat Jan 24, 2015 4:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Problem #7.75b
Replies: 2
Views: 372

Re: Homework Problem #7.75b

Atomization is basically in this case the energy required to turned carbon (graphite) from its solid state into its gaseous state.
by Maria Davila 2I
Thu Jan 22, 2015 10:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Technical Difficulties
Replies: 7
Views: 1081

Re: Technical Difficulties

Such a great video, really helpful and clear steps. Thanks!
by Maria Davila 2I
Thu Jan 22, 2015 7:46 pm
Forum: Phase Changes & Related Calculations
Topic: Heat of Vaporization
Replies: 2
Views: 627

Re: Heat of Vaporization

Thank you Justin, that makes it easier to understand (looking at the units). Thanks !
by Maria Davila 2I
Thu Jan 22, 2015 7:17 pm
Forum: Phase Changes & Related Calculations
Topic: Heat of Vaporization
Replies: 2
Views: 627

Heat of Vaporization

For question 7.35 in the textbook it asks to find the enthalpy of vaporization for CH_4(l) . What is given is the 0.579 mol of CH_4(l) and the heat required 4.76kJ. The solution manuals offers that \Delta H_v_a_p = \frac{q (heat)}{n (mol)} Would the equation used to s...

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