Search found 24 matches

by edhuang
Fri Mar 17, 2017 3:24 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Ring Flip: Final
Replies: 2
Views: 347

Re: Ring Flip: Final

The ring flip is specifying the chair conformations.
by edhuang
Wed Mar 15, 2017 10:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Final 2014 Q3
Replies: 3
Views: 427

Re: Final 2014 Q3

You would have to look at the standard reduction potential table. Alternatively, you could look at the activity series of metals, but that isn't covered in this class.
by edhuang
Sun Mar 12, 2017 10:35 am
Forum: *Alkanes
Topic: Naming Help
Replies: 7
Views: 833

Re: Naming Help

It is alphabetical, and whichever combination of numbers allows for the lowest numbers is the correct name.
by edhuang
Fri Mar 03, 2017 12:10 am
Forum: *Alkanes
Topic: Hydrocarbons memorizations
Replies: 2
Views: 281

Re: Hydrocarbons memorizations

It is probably up to 10, just like the course reader says. Anything above 10 carbon atoms becomes an unnecessarily long hydrocarbon, and the course reader is usually accurate. What is most important is that one memorizes the first four prefixes: " meth, eth, prop, but," as those do not fol...
by edhuang
Fri Feb 24, 2017 6:20 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Nucleophiles
Replies: 2
Views: 319

Re: Nucleophiles

This is very often true, but not always. For example, H2O has a net neutral charge, but because the O atom has a partial negative charge due to its large electronegativity, it can be considered a nucleophile as well. Other examples in the course reader include NH3 and NH2CH3.
by edhuang
Fri Feb 17, 2017 5:32 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Reaction Rate
Replies: 2
Views: 282

Re: Reaction Rate

You would have 3.1^x=9.6. The concentration of the reactant is raised, and you look at to what degree the reaction rate is changed as a result. You do the math, and you get 1.999, which is approximately 2. It is second order.
by edhuang
Thu Feb 09, 2017 4:49 pm
Forum: Balancing Redox Reactions
Topic: 14.5 part A
Replies: 1
Views: 241

Re: 14.5 part A

I'm not sure what you mean because they do cancel out. The final balanced equation is 3O3+Br- -->3O2+BrO3-.
by edhuang
Fri Feb 03, 2017 8:12 pm
Forum: Balancing Redox Reactions
Topic: Easy way to remember when electrons are lost/gained
Replies: 4
Views: 484

Re: Easy way to remember when electrons are lost/gained

This is somewhat related to what we talked about in class, but another mnemonic is "LEO the lion goes GER." Losing Electrons is Oxidation, Gaining Electrons is Reduction.
by edhuang
Mon Jan 30, 2017 8:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs
Replies: 1
Views: 214

Re: Gibbs

I'm not sure what you mean by "decrease," but a negative G indicates that the reaction is spontaneous. The free energy would allow the reaction to proceed.
by edhuang
Thu Jan 26, 2017 11:17 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Clarification regarding irreversible processes
Replies: 2
Views: 246

Re: Clarification regarding irreversible processes

In physics there is an equation where you can calculate the maximum percentage of heat that can be recovered from a process. However, the percentage is, by reasonable standards, nowhere close to 100%. However, in certain instances for the purpose of conceptual understanding, a reversible process is ...
by edhuang
Wed Jan 18, 2017 12:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: CH8 HW#99
Replies: 3
Views: 389

Re: CH8 HW#99

From there you have to find delta H from q, which is q=mcdeltaT. You convert grams of Zinc to moles of Zinc, then you have the delta H you found equal q, 8.5 g of zinc, look up the c of zinc in the table in the back, and delta T, which is final temp minus 25 degrees C. Then you will get the correct ...
by edhuang
Wed Jan 18, 2017 12:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: CH8 HW#99
Replies: 3
Views: 389

Re: CH8 HW#99

The reaction is 2HCl+Zn-->H2+Zn2++Cl2. H2, Cl2, and Zn are in their most stable forms, so their heats of formation are 0. The heat of formation for HCl is -167.16 kJ/mol. For Zn2+ it is -153.89. From there it's delta Hrxn=delta H of products-delta H of reactants.
by edhuang
Thu Dec 01, 2016 9:53 pm
Forum: Bronsted Acids & Bases
Topic: Ka and Kb
Replies: 1
Views: 295

Re: Ka and Kb

No. My chemistry teacher told me that usually after ^10-5 it is safe to make the assumption, but you should always check that the concentration is less than 5% after you finish the calculation. Alternatively, you can plug the x back in the full equation and solve it again until the x does not change...
by edhuang
Wed Nov 16, 2016 6:27 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs. Bronsted acids/bases
Replies: 5
Views: 3214

Re: Lewis vs. Bronsted acids/bases

Atoms generally do not donate protons. Protons do not tend to leave an atom, and do not tend to get added to the atom, generally speaking, unless we are talking about nuclear chemistry in which nuclear reactions cause this to happen. When protons are added to an atom, the atom becomes another elemen...
by edhuang
Thu Nov 10, 2016 2:56 pm
Forum: Naming
Topic: Table of all the ligand names
Replies: 3
Views: 396

Re: Table of all the ligand names

Based on what my TA told me, we will need to memorize all ligands.
by edhuang
Sat Nov 05, 2016 8:02 pm
Forum: Trends in The Periodic Table
Topic: Px py and pz
Replies: 4
Views: 911

Re: Px py and pz

The x in Px stands for the p orbital on the x axis. Likewise for the y in Py and the z in Pz. You use them in hybridization, but the notation just helps you to differentiate between the three orbitals and where they lie.
by edhuang
Mon Oct 31, 2016 8:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angle
Replies: 3
Views: 428

Re: bond angle

The bond angles are simply to memorize. However, they are generally very simple. Most structures have angles of 90, 120, or 180 degrees. The noted exceptions are bent 109.5 degrees, where there are three regions of electron density and one is filled by a lone pair. Another is bent 104.5 degrees, whe...
by edhuang
Thu Oct 27, 2016 4:18 pm
Forum: Lewis Structures
Topic: Formal Charge vs Octet Rule
Replies: 3
Views: 873

Re: Formal Charge vs Octet Rule

Both rules must be applied. However, usually the octet rule is applied first. The octet rule is necessary to make sure each atom has a filled shell, or else it would be chaos. Only AFTER each shell is filled, we start to figure out whether the formal charge is the most favorable. In this case, there...
by edhuang
Sun Oct 23, 2016 10:06 pm
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 3
Views: 347

Re: Lewis Structures

You first obviously need to check for the correct number of electrons. This is a must for Lewis structures. However, you will almost always need to check formal charge for the best possible structure. For example, many times the central atom will have just 4 single bonds, but the central atom may be...
by edhuang
Mon Oct 17, 2016 11:32 pm
Forum: Ionic & Covalent Bonds
Topic: 2.29 c homework
Replies: 2
Views: 278

Re: 2.29 c homework

When n=2 and l isn't given, that means l can be any valid number within n=2. Since l=n-1, l can equal 0 or 1. For 0, it corresponds with the 2s orbital, so 2 electrons there. For 1, it corresponds with the 2p orbitals(3 of them), so 6 electrons there. 2+6=8. Voila
by edhuang
Tue Oct 11, 2016 12:19 am
Forum: Balancing Chemical Reactions
Topic: Diatomic Molecules
Replies: 4
Views: 1073

Re: Diatomic Molecules

The diatomic molecules, quite simply, must be memorized. The elements are hyrogen, oxygen, nitrogen, fluorine, bromine, and chlorine. My TA had some clever mnemonics, but how my friend in high school liked to remember it was "HONFBrCl," pronounced, "honfbrickle." The word would c...
by edhuang
Tue Oct 04, 2016 5:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Calculators [ENDORSED]
Replies: 7
Views: 715

Re: Calculators [ENDORSED]

You have to use scientific calculators, because graphing calculators are programmable. People can program answers and whatnot on graphing calculators to cheat on exams.
by edhuang
Tue Sep 27, 2016 8:53 pm
Forum: Student Social/Study Group
Topic: Chemistry Jokes
Replies: 31
Views: 4383

Re: Chemistry Jokes

Oxygen is recruiting elements to play tag.

He goes to Potassium and says, "Do you want to play?"

Potassium says, "K."

He then goes to Sodium and asks, "Do you want to play?"

Sodium goes, "Na."
by edhuang
Tue Sep 27, 2016 8:50 pm
Forum: Significant Figures
Topic: Sig Figs Throughout Problems
Replies: 12
Views: 2905

Re: Sig Figs Throughout Problems

So in high school chemistry (regular and AP) I was used to using molar masses down to the hundredths, because that was the periodic table I was given. I was wondering if I could still round to the hundredths for molar masses in this class, though the periodic table rounds to the thousandths and some...

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