## Search found 6 matches

Tue Jan 13, 2015 7:14 pm
Forum: Calculating Work of Expansion
Topic: Error in Solutions Manual 7.3
Replies: 1
Views: 302

### Re: Error in Solutions Manual 7.3

For future reference this was also on the solution manual errors document that Lavelle has on his website!

https://lavelle.chem.ucla.edu/class-websites/chem14b/
Fri Jan 09, 2015 6:55 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess' Law & Standard enthalpy subtr. 7.13A Self-test
Replies: 1
Views: 372

### Re: Hess' Law & Standard enthalpy subtr. 7.13A Self-test

When you flip the second equation, you change the sign of the change in enthalpy This occurs when you're trying to cancel out components that are not in the final equation (when it's in the product of one eq and reactant of another in equal quantities), and when you're trying to get the component in...
Fri Jan 09, 2015 6:44 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 7.59
Replies: 1
Views: 394

### Re: Question 7.59

The combustion of graphite -> -393.51 kJ/mol The combustion of diamond -> -395.41 kJ/mol But since you want to create diamond from graphite, the formation of diamond -> +395.41 kJ/mol So it's -393.51 + 395.41 Another way of looking at it is that diamond is less stable and has more energy than graphi...
Thu Jan 08, 2015 5:18 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: 1488

### Re: Question 7.27, Gas constant temperature units

Celsius and Kelvin go by the same increments though, so the change in temperature should be the same regardless of your unit.
Thu Jan 08, 2015 10:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of Zn(s)
Replies: 2
Views: 9266

### Re: Standard enthalpy of Zn(s)

Zinc is oxidized by HCl so the equation is as follows: 2 HCl (aq) + Zn (s) -> H2 (g) + ZnCl2 (aq), in which ZnCl2 is essentially Zn2+ and 2 Cl- And according to the appendix, the enthalpy of formation for Zn2+ is -153.89 kj/mol Edit: to elaborate, here are the calculations http://i.imgur.com/00Ipaq4...
Mon Jan 05, 2015 2:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Why E=0 for isothermal processes?
Replies: 6
Views: 1396

### Re: Why E=0 for isothermal processes?

I'm still somewhat confused. Reversible, isothermal expansion of an ideal gas does work (pages 244-245 in the textbook). If the system does work, doesn't its internal energy change since change in U = q + w? However, internal energy is a state function, and if the temperature does not change, the to...