## Search found 13 matches

Sat Mar 14, 2015 7:08 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 2010 Finals #6C Reaction Mechanism
Replies: 2
Views: 587

### Re: 2010 Finals #6C Reaction Mechanism

In this particular problem, you're asked to draw the mechanism, so you do have to come up with the steps. In the question, it tells you that the reaction is "acid-catalyzed", and suggests that you use H+ or H30+. (remember that if something is in basic conditions, it means that there's OH-...
Sat Mar 14, 2015 6:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 2012 Final Q1B Enthalpy of a reaction
Replies: 3
Views: 1133

### Re: 2012 Final Q1B

You don't have enough information to calculate the delta H at 398K, the way you did for 298K in the first part of 1B. So you have to break it up into steps. Then you can combine the steps, since enthalpy is a state function and doesn't care about how you got from point a to point b, as long as you s...
Wed Mar 11, 2015 7:18 pm
Forum: *Alkanes
Topic: Geometric isomers for C6H14!
Replies: 4
Views: 787

### Re: Geometric isomers for C6H14!

For your first question, when a part of the main chain is put in parentheses because it's being repeated, then that's just to make things simpler, and it can still be written out if you want to write it without the parentheses. Side chains, however (for example, the methyl group), do need to be in p...
Mon Feb 16, 2015 11:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 13.11(a) Why do we reverse the anode reaction?
Replies: 3
Views: 676

### Re: Homework 13.11(a) Why do we reverse the anode reaction?

If you mean the fact that you take the oxidation half reaction that happens in the anode and reverse it, then you can do that so that it's written as a reduction half reaction. If it's written that way, then you can use the standard reduction potential for that half reaction to calculate the overall...
Wed Feb 11, 2015 3:52 pm
Forum: Calculating Work of Expansion
Topic: Calculating final temp & enthalpy for an ideal monatomic gas
Replies: 7
Views: 1178

### Re: Calculating final temp & enthalpy for an ideal monatomic

That seems right to me! Where did you get this problem, maybe you can look up the solution online or something?
Wed Feb 11, 2015 1:36 pm
Forum: Calculating Work of Expansion
Topic: Calculating final temp & enthalpy for an ideal monatomic gas
Replies: 7
Views: 1178

### Re: Calculating final temp & enthalpy for an ideal monatomic

That seems right to me! Where did you get this problem, maybe you can look up the solution online or something?
Wed Feb 11, 2015 12:54 pm
Forum: Calculating Work of Expansion
Topic: Calculating final temp & enthalpy for an ideal monatomic gas
Replies: 7
Views: 1178

### Re: Calculating final temp & enthalpy for an ideal monatomic

Actually, now that I think about it, doesn't q=deltaH at constant pressure?
Wed Feb 11, 2015 12:48 pm
Forum: Calculating Work of Expansion
Topic: Calculating final temp & enthalpy for an ideal monatomic gas
Replies: 7
Views: 1178

### Re: Calculating final temp & enthalpy for an ideal monatomic

The first part (calculating the final temperature) is fairly straightforward. I used the equation q=n*C*deltaT. For the heat capacity (C), you were told to assume that it is an ideal, monatomic gas at constant pressure, so you would use 5/2 R as your heat capacity (this is given on the formula sheet...
Sat Feb 07, 2015 7:14 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculating The Energy Changes When Heating An Ideal Gas
Replies: 4
Views: 1543

### Re: Calculating The Energy Changes When Heating An Ideal Gas

If you look at page 27 in the course reader, you see that we're given the equation deltaU=3/2*nRdeltaT for an ideal gas. It follows that if the expansion is happening isothermally, then since deltaT is 0, deltaU is as well. So deltaU is zero for the isothermal expansion of any ideal gas. If you're c...
Sat Feb 07, 2015 6:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy Midterm 2011 2.A
Replies: 1
Views: 467

### Re: Standard Enthalpy Midterm 2011 2.A

The phases are what's important here. In the 1st reaction (2Al(s)+6HCl(aq)--->2AlCl 3 (aq)+3H 2 (g)), the AlCl 3 is aqueous , but if you look at the reaction that you're trying to end up with, it has solid AlCl 3 , so you need to use the 4th reaction (AlCl 3 (s)--->AlCl 3 (aq)) to cancel out the aqu...
Wed Nov 12, 2014 1:19 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sigma Pz in MO diagram of atoms with z>8
Replies: 1
Views: 444

### Re: Sigma Pz in MO diagram of atoms with z>8

The fact that he called it "symmetrical" confused me too. In this case, it's less like the antibonding being "symmetric" to the bonding, and more like a reflection. Imagine a horizontal line between the bonding and the antibonding; if you fold the paper along that line, the sigma...
Mon Nov 10, 2014 9:35 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7828
Views: 1086912

### Re: Chemistry Jokes

I heard Potassium and Oxygen went on a date....It went OK

Q: What do you do with a sick chemist?
A: If you can't helium, and you can't curium, then you might as well barium

Q: What is the name of 007's Eskimo cousin?
A: Polar Bond
Sat Nov 08, 2014 5:20 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Some MO diagram specifics
Replies: 1
Views: 356

### Re: Some MO diagram specifics

The only one that matters as far as naming is pz in the molecular orbital. Sigma has to be pz, so then px and py are both pi. Other than that it doesn't really matter, but in the atomic orbitals, most people go in alphabetical order (px, py, pz).