Search found 22 matches
- Wed Mar 15, 2017 4:55 pm
- Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
- Topic: Eclipsed Hydrogens for Boat Conformation of Cyclohexanes
- Replies: 1
- Views: 498
Eclipsed Hydrogens for Boat Conformation of Cyclohexanes
On page 113 of the Intro to Organic Chemistry book, when talking about the boat conformation for cyclohexane, it says that "the four C-H bonds on the sides are eclipsed." Which C-H bonds is this referring to? It says "side," but looking at the diagram of the molecule, I would hav...
- Sun Mar 05, 2017 4:30 pm
- Forum: *Alkanes
- Topic: Naming Organic Molecules
- Replies: 5
- Views: 1086
Re: Naming Organic Molecules
Yes, the longest chain is the parent chain (it can bend around when drawing the structure).
- Sun Feb 26, 2017 5:44 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3614216
Re: Post All Chemistry Jokes Here
Prostitute Teacher: Describe hydrogen.
Student: It is a prostitute element.
Teacher: Who taught you that?
Student: You said it does not belong to a particular group and it reacts with almost all the elements in the periodic table.
Student: It is a prostitute element.
Teacher: Who taught you that?
Student: You said it does not belong to a particular group and it reacts with almost all the elements in the periodic table.
- Tue Feb 21, 2017 12:27 am
- Forum: General Rate Laws
- Topic: Hw 15.27 and 15.35
- Replies: 2
- Views: 612
Re: Hw 15.27 and 15.35
Also another note, since I got tripped up here, with a first-order reaction, t = ln[A 0 /A] / k. If A = 1/8 A 0 , the equation would be t = ln[A 0 / (1/8 * A 0 )] / k, so the A 0 would cancel out. With a second-order reaction however, you need to include the initial concentration in your calculation...
- Sun Feb 12, 2017 1:57 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E and E°, G and G°
- Replies: 3
- Views: 2098
Re: E and E°, G and G°
Well generally, ° means it's under standard conditions. So for example, E is different from E° when the concentrations of the products and reactants are not the same.
- Sun Feb 05, 2017 3:54 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3614216
Re: Post All Chemistry Jokes Here
What do you call a periodic table with gold missing?
Au revoir!
Au revoir!
- Sat Jan 28, 2017 10:07 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: HW 9.13
- Replies: 3
- Views: 708
Re: HW 9.13
I thought that the equation using R was only for volume or pressure (ΔS = nR ln(V2/V1)). Is it the same for temperature too? Where did that equation come from?
- Sat Jan 28, 2017 5:03 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy Change Relating to Temperature
- Replies: 1
- Views: 773
Entropy Change Relating to Temperature
I know that ΔS = q/T, so I understand (using the equation) that the entropy change is smaller at higher temperatures. But why is this so, conceptually?
- Fri Jan 27, 2017 11:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Calculating delta H of a reaction
- Replies: 2
- Views: 683
Re: Calculating delta H of a reaction
That's because the enthalpy of formation for elements in their most stable form equals 0. O2 is the most stable form for oxygen.
- Thu Jan 19, 2017 4:14 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 1
- Views: 384
Re: Bond Enthalpies
You would have to draw out the Lewis structures for each compound in order to determine the bonds between certain atoms. But I just assume all bonds in the structures are broken and then reformed in my calculations (because any that weren't actually broken would just cancel out since you subtract th...
- Sat Jan 14, 2017 10:16 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Standard Reaction Enthalpy Property
- Replies: 2
- Views: 621
Re: Standard Reaction Enthalpy Property
Standard reaction enthalpies refer to the changes in enthalpy for an entire reaction when the reactants change into products. Standard enthalpies of formation refer to the change in enthalpy for a particular substance (e.g. one particular reactant or one particular product) which are then added/subt...
- Wed Nov 30, 2016 4:10 pm
- Forum: *Titrations & Titration Calculations
- Topic: Weak base-strong acid
- Replies: 1
- Views: 461
Re: Weak base-strong acid
It's basically showing why the stoichiometric point is not exactly at ph7 for weak acids or bases. NH 3 + HCl + H 2 O <-> H 2 O + NH 4 + + Cl - ^This part shows how the salt donates its proton to the base, forming a conjugate acid (NH 4 + ). Since it's a weak base, it's at an equilibrium, so that so...
- Wed Nov 30, 2016 3:59 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Hydronium and Hydroxide
- Replies: 2
- Views: 695
Re: Hydronium and Hydroxide
I think we usually consider the solvent to be water, so it shows the transfer of the proton from the acid to water to produce the hydronium ion. Not sure if that answered your question.
- Mon Nov 14, 2016 4:45 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Quiz #3 [ENDORSED]
- Replies: 7
- Views: 1578
Re: Quiz #3 [ENDORSED]
There are some practice questions from the Quiz 2 preparations that actually covered MOs.
- Tue Nov 01, 2016 1:18 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Molecular Orbitals between Two Atoms that are Different Elements
- Replies: 1
- Views: 491
Molecular Orbitals between Two Atoms that are Different Elements
This is based off homework question 4.57. I understand why the bonding orbitals would be closer to the more electronegative atom in energy (because of the greater pull on electrons), but why are the antibonding orbitals closer to the less electronegative atom in energy?
- Tue Nov 01, 2016 12:25 pm
- Forum: Hybridization
- Topic: s-character of hybrids
- Replies: 1
- Views: 566
s-character of hybrids
This is referring to the homework question 4.43. What does it mean by the s-character of the hybrids?
- Tue Oct 25, 2016 11:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Lewis Structure of Ionic vs. Covalent
- Replies: 3
- Views: 653
Re: Lewis Structure of Ionic vs. Covalent
What about for compounds like potassium phosphide or sodium hypochlorite? (textbook exercise 3.39)
- Tue Oct 25, 2016 10:14 pm
- Forum: Ionic & Covalent Bonds
- Topic: Lewis Structure of Ionic vs. Covalent
- Replies: 3
- Views: 653
Lewis Structure of Ionic vs. Covalent
Based on the name of the compound itself (e.g. ammonium chloride), how do you know if the compound is ionically or covalently bonded when drawing the Lewis Structure?
- Sat Oct 22, 2016 6:27 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Radii Trends
- Replies: 1
- Views: 513
Re: Ionic Radii Trends
The s-block forms cations (with a positive charge), so the loss of an electron/electrons causes a smaller radius. However, the radii also decreases due to the increasing nuclear charge. The p-block forms anions (with a negative charge), so the addition of an electron/electrons causes a larger radius...
- Sat Oct 22, 2016 6:22 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Determining Resonance
- Replies: 3
- Views: 841
Re: Determining Resonance
Also, if an atom is double bonded to one atom of a certain element X as well as single bonded to more atoms of that same element X (that aren't also bonded to anything else), there will be resonance.
- Sat Oct 08, 2016 9:27 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty of Momentum and Position [ENDORSED]
- Replies: 1
- Views: 563
Uncertainty of Momentum and Position [ENDORSED]
Can't you not know with zero uncertainty either the momentum or position since that would effectively make Heisenberg's Indeterminacy Equation 0 = h/4π, which is not true? (As in, shouldn't there be at least some uncertainty in both the momentum and position?)
- Thu Oct 06, 2016 11:39 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Why h/4π?
- Replies: 2
- Views: 1033
Why h/4π?
Where does the h/4π in Heisenberg's Indeterminacy Equation come from? Was it found experimentally? What determined that value?