Search found 10 matches

by Douglas Dean
Tue Mar 15, 2016 2:46 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7726
Views: 1046008

Re: Chemistry Jokes

I thought this was funny! :D

Image
by Douglas Dean
Tue Mar 08, 2016 11:10 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Final 2013 Q6A
Replies: 1
Views: 314

Final 2013 Q6A

The question asks to name the molecule given. It is a cyclohexene, so it is a hexagon with one double bond, and then it has 4 methyl groups attached. The answer given is 1,5,5,6-tetramethylcyclohexene. Why are the methyls numbered 1,5,5,6 instead of 2,3,4,4? In both cases the double bond is on carbo...
by Douglas Dean
Tue Mar 08, 2016 10:47 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Final 2013 #4A
Replies: 2
Views: 393

Final 2013 #4A

4a. When dissolved oxygen in water comes in contact with metal iron, rust is formed by the following reaction: 2Fe(s) + 2H2O(l) + O2(aq) --> 2Fe(OH)2(s) Enaut=+0.840V Two different concentrations of oxygen were dissolved in separate water droplets on an iron surface at 298K. The reactions were allow...
by Douglas Dean
Tue Feb 09, 2016 4:15 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Midterm 2015 #4/5
Replies: 1
Views: 236

Midterm 2015 #4/5

B) Ron mispronounces the spell, causing his balloon to expand uncontrollably. The balloon starts at 3.3 L and room temperature (298) but ends up at a whopping 9.2x10^5 L and 333K, forcing the entire class to flee the classroom. Calculate deltaS for Ron's balloon. Assume that Helium in the balloon is...
by Douglas Dean
Sun Jan 24, 2016 11:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Another Question about Quiz 2014 #9
Replies: 5
Views: 536

Re: Another Question about Quiz 2014 #9

Thanks so much Michael! That makes sense, I was just using deltaH not considering it as a reactant. And for the other question, I'm pretty sure deltaS refers to the summation of the entropy of the products minus the summation of the entropy of the reactants. Thus in this problem, you would do deltaS...
by Douglas Dean
Sun Jan 24, 2016 7:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Another Question about Quiz 2014 #9
Replies: 5
Views: 536

Re: Another Question about Quiz 2014 #9

Chem_Mod wrote:Hi,
Please post the question in full


Sorry about that!

9. Calculate DeltaGr for the balanced reaction showing the decomposition of mercury (II) oxide at 298K.

HgO(s) --> Hg(l) + O2(g)
DeltaHf in kj/mol: -90.83
S in j/kmol: 70.29 76.02 205.14
by Douglas Dean
Sun Jan 24, 2016 3:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Another Question about Quiz 2014 #9
Replies: 5
Views: 536

Another Question about Quiz 2014 #9

I understand most of the problem and how to get the right answer, you use deltaG = deltaH - TdeltaS, but how do you know that deltaH ends up being a positive value? The value given is negative, thats why it confuses me. Thanks :D
by Douglas Dean
Sun Jan 24, 2016 1:48 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Quiz Question #3 for Winter 2015
Replies: 1
Views: 290

Quiz Question #3 for Winter 2015

I understand how to calculate the work, since it is reversible work has to be done and you use w=-nRTln(V2/V1). However, how do you know that deltaU is zero? And why is q a positive number instead of being zero since the change in temperature is 0 (isothermal)? Thanks :D 3. If 2 mol of an ideal gas ...
by Douglas Dean
Tue Jan 19, 2016 2:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Quick Question About Isothermal Reactions
Replies: 1
Views: 260

Quick Question About Isothermal Reactions

What is a reversible isothermal reaction and which equation do we use for it?
by Douglas Dean
Fri Jan 15, 2016 5:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Quick Question about Force Equation
Replies: 1
Views: 218

Quick Question about Force Equation

In the equation F = P x A, or in W = P x A x D, does the A stand for normal area or surface area?

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