Search found 20 matches

by Edwin Ng 1G
Thu Mar 10, 2016 12:15 am
Forum: *Alkenes
Topic: 1,6-dichlorocyclohexene
Replies: 2
Views: 583

Re: 1,6-dichlorocyclohexene

It doesn't matter, but your two choices for naming are 1,6-dichlorocyclohexene or 2,3-dichlorocyclohexene. It wouldn't be 1,2-dichlorocyclohexene because the double bond wouldn't be between the first and second carbon. The first one is correct because 1<2.
by Edwin Ng 1G
Sun Feb 28, 2016 11:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Organic CHemistry Workbook
Replies: 1
Views: 415

Re: Organic CHemistry Workbook

Check the back of the book!
by Edwin Ng 1G
Sun Feb 21, 2016 9:37 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Hot Spots: Pg 87 of course reader
Replies: 1
Views: 304

Re: Hot Spots: Pg 87 of course reader

If there is a C=C double bond, the pi bond can break and form a bond with the electrophile. This is not the case with a C-C single bond because it doesn't have a pi bond.
by Edwin Ng 1G
Sun Feb 14, 2016 11:33 am
Forum: General Rate Laws
Topic: Course Reader 2nd Order Rxn
Replies: 2
Views: 475

Re: Course Reader 2nd Order Rxn

When you integrate (1/[A]2) it becomes (-1/[A]), and so the two negatives cancel
by Edwin Ng 1G
Tue Feb 09, 2016 1:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2014 #8
Replies: 2
Views: 384

Re: Midterm 2014 #8

You need to match the half-reactions with the total reaction given (HF -> H + F). Because the first equation with E=3.03 was flipped, that one becomes negative.
by Edwin Ng 1G
Tue Feb 02, 2016 3:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 1 Score
Replies: 2
Views: 721

Re: Quiz 1 Score

Most likely the week after you take the quiz. If not, then the second week for sure.
by Edwin Ng 1G
Mon Jan 25, 2016 10:22 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity Units?
Replies: 2
Views: 523

Re: Heat Capacity Units?

There isn't a reason why. I think it's just more convenient.

One mole of a compound is usually more than one gram of a compound, so if they were both expressed in joules, the molar heat capacity can become a large number.
by Edwin Ng 1G
Tue Jan 19, 2016 3:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Change
Replies: 1
Views: 303

Re: Entropy Change

When you take away energy/heat from the 800K reservoir, entropy decreases. Less energy means that the molecules are not moving as fast, which lead to less disorder
by Edwin Ng 1G
Sat Jan 16, 2016 2:19 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework question
Replies: 1
Views: 336

Re: Homework question

Most likely the numbers you used for the calculation are different than what the book used, in that yours might have been more exact. On a test, if your final answer is slightly off compared to the answer key but the all the work done is correct, you will most likely get full credit.
by Edwin Ng 1G
Fri Jan 08, 2016 11:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Understanding Table 8.8 (Standard Enthalpies of Combustion)
Replies: 1
Views: 301

Re: Understanding Table 8.8 (Standard Enthalpies of Combusti

Yep, a combustion reaction is written like this

(Substance) + O2 -> H2O + O2

When written like this, the reaction is exothermic (the substance burns and releases heat) and so delta H is negative
by Edwin Ng 1G
Sun Nov 29, 2015 2:16 am
Forum: Bronsted Acids & Bases
Topic: Stong Acid/Base
Replies: 2
Views: 665

Re: Stong Acid/Base

You can probably memorize the strong acids/bases since there aren't a lot.

Here's a website that lists the 7 strong acids and 8 strong bases.

http://mccord.cm.utexas.edu/courses/summer2005/ch302/strong.html
by Edwin Ng 1G
Sun Nov 29, 2015 2:12 am
Forum: Lewis Acids & Bases
Topic: Acids & Bases
Replies: 2
Views: 649

Re: Acids & Bases

In general.. Acidic oxides are formed when the oxygen is bound to a nonmetal . Basic oxides are formed when the oxygen is bound to a metal . Amphoteric oxides are formed when the oxygen is bound to a metalloid . For more info see this link: http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive...
by Edwin Ng 1G
Wed Nov 18, 2015 6:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HF vs HCl
Replies: 1
Views: 1250

Re: HF vs HCl

The atomic radius of the F atom is smaller than the Cl atom and so the bond in HF is stronger, making it harder to dissociate.

For some of the halogens, HI is a stronger acid than HBr, which is stronger than HCl, which is stronger than HF.
by Edwin Ng 1G
Thu Nov 12, 2015 11:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Creating a "new initial" for the ICE box (Q 11.67)
Replies: 3
Views: 651

Re: Creating a "new initial" for the ICE box (Q 11.67)

Even when I use the new initial values of 4,0 and 2, my calculator spits out x=0 instead of 2.6*10^-33. On a side note, will we be dealing with these very small numbers on quizzes and exams?
by Edwin Ng 1G
Thu Nov 05, 2015 7:09 pm
Forum: Naming
Topic: Aqua versus Hydro in Coordination Compounds
Replies: 1
Views: 375

Re: Aqua versus Hydro in Coordination Compounds

Do you have an example? You could be mixing up OH2 (aqua) with OH- (hydroxido)
by Edwin Ng 1G
Thu Oct 29, 2015 1:02 am
Forum: Formal Charge and Oxidation Numbers
Topic: Selecting Most Likely Atom Arrangement
Replies: 1
Views: 439

Re: Selecting Most Likely Atom Arrangement

You can calculate the net charge of -1 by calculating the formal charge on each atom and adding them all up (step 4 in example 3.6).

Alternatively, you know that KSCN is a neutral compound, and since K has a charge of +1, SCN is -1.
by Edwin Ng 1G
Sun Oct 25, 2015 1:53 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Precise Bond Angles
Replies: 1
Views: 331

Re: Precise Bond Angles

Well, here are two bent molecules with different bond angles, SCL 2 (103°) and H 2 O (104.45°) https://en.wikipedia.org/wiki/Sulfur_dichloride"onclick="window.open(this.href);return false; https://en.wikipedia.org/wiki/Properties_of_water"onclick="window.open(this.href);return false; So there isn't ...
by Edwin Ng 1G
Mon Oct 19, 2015 12:48 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Boron and Fluorine
Replies: 1
Views: 273

Re: Boron and Fluorine

Boron only has 3 valence electrons for it to share with other atoms so it usually forms 3 bonds, which is also enough for a formal charge of 0. Fluorine usually forms an octet.
by Edwin Ng 1G
Sat Oct 10, 2015 3:35 pm
Forum: Significant Figures
Topic: Answer Specificity
Replies: 2
Views: 537

Re: Answer Specificity

My TA said that if the last digit is off by 1 then it should be okay. If the solution manual says 4.3x10^4, 4.4 would be okay, but 4.5 would not be correct. Anyone else have an idea?
by Edwin Ng 1G
Mon Oct 05, 2015 12:00 am
Forum: Quantum Numbers and The H-Atom
Topic: How to find beginning & ending energy levels with wavelength
Replies: 1
Views: 458

Re: How to find beginning & ending energy levels with wavele

Well I just plugged in numbers and checked if it works. A bit more insight... the problem states that the wavelength is in the ultraviolet spectrum, and for hydrogen, that corresponds to the Lyman series! And for this, n1 = 1. .88848=((1/n1^2)-(1/n2^2)) You also know n2 > n1 (otherwise the value on ...

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