Search found 31 matches
- Sun Mar 19, 2017 6:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 951742
Re: Saying Thank You to Dr. Lavelle
Dr. Lavelle, Thank you for not only helping me understand chemistry better, but also for helping ease the transition from high school into college. You have been understanding every step of the way and have supported me, as well as your thousands of other students, in this exciting, yet nerve-wracki...
- Sun Mar 12, 2017 12:11 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
If you're not part of the solution, you're part of the precipitate.
What's "HIJKLMNO"?
H2O
Why does a hamburger have lower energy than a steak?
It's in the ground state
What's "HIJKLMNO"?
H2O
Why does a hamburger have lower energy than a steak?
It's in the ground state
- Thu Mar 09, 2017 12:39 am
- Forum: *Electrophilic Addition
- Topic: Electrophilic Addition Example in Quiz 3 Prep
- Replies: 2
- Views: 1412
Re: Electrophilic Addition Example in Quiz 3 Prep
Electrophilic addition reactions are always two step mechanisms (and therefore always have two transition states). On the other hand SN2 reactions are all one step reactions with one transition state.
- Sun Mar 05, 2017 8:55 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
Did you hear about the guy who got cooled to absolute zero ?
He's 0K now
What's a girl's future best friend?
Carbon
C (graphite) -> C (diamond)
He's 0K now
What's a girl's future best friend?
Carbon
C (graphite) -> C (diamond)
- Wed Mar 01, 2017 4:13 pm
- Forum: *Complex Reaction Coordinate Diagrams
- Topic: IUPAC vs. Common names
- Replies: 1
- Views: 1436
Re: IUPAC vs. Common names
Common names apply to specific molecules, but Lavelle said that he's not going to specify the type of naming that we must do (IUPAC vs common), so we can just use IUPAC any time a question asks to name a molecule.
- Sat Feb 25, 2017 5:35 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
What do you call iron blowing in the wind?
Febreze
What do dipoles say in passing"
"Have you got a moment?"
Febreze
What do dipoles say in passing"
"Have you got a moment?"
- Wed Feb 22, 2017 1:28 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Speed of reaction
- Replies: 1
- Views: 639
Re: Speed of reaction
The question will clarify which elementary reaction is faster and slower because you can't determine that by just looking at the steps.
- Sun Feb 19, 2017 1:12 pm
- Forum: General Rate Laws
- Topic: Pre-Equilibrium Approach
- Replies: 1
- Views: 547
Re: Pre-Equilibrium Approach
We know that step two is going to be the slow step because there is going to be a buildup of the intermediate from step one; therefore, because step one is progressing so quickly, there will be a bottle-neck effect.
- Sun Feb 12, 2017 10:46 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding Ka
- Replies: 2
- Views: 714
Re: Finding Ka
Kb would apply to a basic reaction, so I assume that you would solve it the same way as you would for an acidic reaction.
- Thu Feb 09, 2017 10:48 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 3
- Views: 783
Re: Cell Diagrams
The electrode (inert conductor) should sandwich the molecules being oxidized and reduced, but other than that the order of the molecules within the anode and cathode does not matter. It's important to know where to put the lines that separate the molecules- draw a line when the molecules are in diff...
- Sun Feb 05, 2017 4:18 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
An optimist sees the glass half-full and a pessimist sees the glass-half empty, but the chemist sees the glass half-filled with liquid and half-filled with gas... unless the system is in a vacuum.
- Mon Jan 30, 2017 9:39 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.65
- Replies: 1
- Views: 564
Re: 8.65
First, you must create an equation in which the only product is N2O5 by manipulating the two given equations. Once you attain the standard enthalpy of the reaction for your new equation, solve for the standard enthalpy of formation for N2O5 by using the formula: DeltaH = 2DeltaH(N2O5) - 3DeltaH(O2)-...
- Wed Jan 25, 2017 1:48 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Homework Question 9.15 (a)
- Replies: 1
- Views: 686
Re: Homework Question 9.15 (a)
DeltaS=q/T = DeltaH/T = ((1.00 mol)(-6.01 kJ/mol))/(273.2 K).
-6.01 kJ/mol is the enthalpy of fusion (melting), and since freezing is the opposite of melting you just take the negative of delta H. Also, the freezing point of water is at 273.2 K- both of these values are found in table 8.3.
-6.01 kJ/mol is the enthalpy of fusion (melting), and since freezing is the opposite of melting you just take the negative of delta H. Also, the freezing point of water is at 273.2 K- both of these values are found in table 8.3.
- Sun Jan 22, 2017 11:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.57
- Replies: 4
- Views: 916
Re: 8.57
You're adding up the enthalpies of the reaction. You are given an equation and the enthalpies of combustion for each of the individual molecules, so when you create a combustion equation for each of the molecules (remember that combustion is a molecule + oxygen -> carbon dioxide + water) you will ha...
- Sun Jan 22, 2017 11:13 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Homework 8.73 a
- Replies: 3
- Views: 791
Re: Homework 8.73 a
I'm not sure why the solution manual doesn't break the C-H bonds that are on the reactants side (as well as the products side), but this is how I did it: break 1 C-C triple bond: (3 mol)(837 kJ/mol) break 2 H-C single bonds: (3 mol)(412 kJ/mol) form 6 C-C resonance bonds: -(6 mol)(518 kJ/mol) form 6...
- Wed Jan 18, 2017 8:57 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Calorimeter questions
- Replies: 2
- Views: 569
Re: Calorimeter questions
When HCl and NaOH react with each other, H2O and NaCl form, but because NaCl is a salt, it doesn't react with anything. Whenever you are using density, you should also use specific heat capacity because density times volume equals mass which can be multiplied by specific heat capacity and temperatur...
- Thu Jan 12, 2017 1:58 pm
- Forum: Phase Changes & Related Calculations
- Topic: Most Helpful Resource
- Replies: 14
- Views: 2593
Re: Most Helpful Resource
I found the UA hours especially helpful because there are so many of them, but also because there are fewer people there so you can ask more questions. Also, since the UAs are usually third- or forth-years they can give you practice problems from earlier versions of the course reader.
- Wed Nov 30, 2016 5:00 pm
- Forum: *Indicators
- Topic: Importance of Indicators
- Replies: 2
- Views: 5362
Re: Importance of Indicators
I think we need to know what they are (weak acids that change color when the stoichiometric point is reached), but when I asked Lavelle during office hours, he said that we don't need to know the colors.
- Wed Nov 30, 2016 4:57 pm
- Forum: General Science Questions
- Topic: chemical equilibrium
- Replies: 1
- Views: 782
Re: chemical equilibrium
If the reaction is endothermic (requires heat), then heating the equation will favor products (forward reaction) whereas if the reaction is exothermic (releases heat), then heating will favor reactants (reverse reaction). Also, since pressure and volume are inversely proportional (as pressure increa...
- Thu Nov 24, 2016 9:56 am
- Forum: Lewis Acids & Bases
- Topic: page 161 of the course reader
- Replies: 1
- Views: 603
Re: page 161 of the course reader
The question is asking for the pH of NH4Cl (an acidic salt) and because it dissociates into NH3 and H3O+, we need to find the concentration of H3O+ by doing an ICE chart. At equilibrium we find that the concentration of of H3O+ is x, and by solving for x we get 9.2e-6, so by using the equation pH=-l...
- Wed Nov 16, 2016 12:19 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: MO diagrams for ions
- Replies: 3
- Views: 1156
MO diagrams for ions
If you are given an ion such as NO+ and are told to draw the MO diagram for it, which atom would the electron be taken from? Would the N have one less electron because it is less electronegative than O and therefore able to lose an electron more easily?
- Tue Nov 08, 2016 11:14 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
What kind of fish is made out of two sodium atoms?
Tuna (2Na)
Tuna (2Na)
- Fri Nov 04, 2016 1:34 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: 4.61 Homework Question
- Replies: 3
- Views: 964
Re: 4.61 Homework Question
CO:(sigma 2s)^2 (sigma 2s*)^2 (pi 2p)^4 (sigma 2p)^22. Bond order=3
CO+: (sigma 2s)^2 (sigma 2s*)^2 (pi 2p)^4 (sigma 2p)^11. Bond order=2.5
Because CO has a higher bond order, it has a stronger bond.
CO+: (sigma 2s)^2 (sigma 2s*)^2 (pi 2p)^4 (sigma 2p)^11. Bond order=2.5
Because CO has a higher bond order, it has a stronger bond.
- Thu Oct 27, 2016 3:03 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 4856952
Re: Post All Chemistry Jokes Here
Whats the chemical formula for banana?
BaNa2
BaNa2
- Thu Oct 27, 2016 2:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MidTerm Review [ENDORSED]
- Replies: 4
- Views: 1189
Re: MidTerm Review [ENDORSED]
Lavelle said that the best way to study for the midterm is by reviewing the past two quizzes which means that the midterm would be up to chapter three. However, I'm not sure if he would put anything from chapter four on the midterm, but if I hear anything I'll update this post.
- Tue Oct 25, 2016 4:06 pm
- Forum: Lewis Structures
- Topic: Lewis Structure Octet Rule Exceptions
- Replies: 3
- Views: 1632
Re: Lewis Structure Octet Rule Exceptions
H, He, Li, and Be do not follow the octet rule. Also, B can form less than an octet, such as BF3, but it can also attain an extra electron to fulfill the octet rule, such as BF4^-
- Tue Oct 25, 2016 3:58 pm
- Forum: Resonance Structures
- Topic: Resonance structures [ENDORSED]
- Replies: 3
- Views: 1033
Re: Resonance structures [ENDORSED]
It's possible to have resonance structures in which the resonance occurs with different elements so long as, in this case, nitrogen and oxygen do not have expanded octets. Also, be aware of the formal charge; if the compound is neutral and double bonding the nitrogen or oxygen gives you an overall n...
- Fri Oct 21, 2016 2:52 pm
- Forum: Resonance Structures
- Topic: Radicals
- Replies: 3
- Views: 846
Re: Radicals
Radicals will react with an electron from a DNA molecule and oxidize it, but antioxidants (like the ones in blueberries) catch radicals before the can cause damage.
- Wed Oct 12, 2016 5:39 pm
- Forum: SI Units, Unit Conversions
- Topic: Conversions
- Replies: 2
- Views: 537
Re: Conversions
For all equations that include joules use kilograms- this includes the De Broglie equation and Heisenberg Uncertainty Principle. Also, always use liters for molarity. To remember to convert units just look at the units you want in your answer and keep in mind that 1 J = 1 kg*m^2/s^2.
- Wed Oct 05, 2016 3:32 pm
- Forum: Properties of Electrons
- Topic: Atomic Spectra Requirements [ENDORSED]
- Replies: 3
- Views: 867
Re: Atomic Spectra Requirements [ENDORSED]
For the chapter one homework questions, it asked to determine the type of electromagnetic radiation from the wavelength calculated, so I would assume that we should know the different regions for the quiz next week.
- Wed Sep 28, 2016 9:09 pm
- Forum: Properties of Light
- Topic: Kinetic Energy
- Replies: 4
- Views: 1299
Re: Kinetic Energy
Total energy-threshold energy=excess energy describes the photoelectric effect in steps. In other words, a certain amount of energy is inputed by a photon and the process of removing an electron takes up some energy, but if there is some left over, then the electron takes the excess/kinetic energy w...