Search found 142 matches

by Justin Le 2I
Tue Dec 02, 2014 10:12 pm
Forum: Naming
Topic: Elements before the brackets
Replies: 4
Views: 545

Re: Elements before the brackets

An example would be K2[Ni(CN)4]

Here, the K is outside the bracket and serving as a cation, just like in KCl.
by Justin Le 2I
Tue Dec 02, 2014 10:10 pm
Forum: Naming
Topic: Quiz 3 prep #4
Replies: 3
Views: 437

Re: Quiz 3 prep #4

Since the question does not have the word ion, you know that you need to make the compound neutral.
by Justin Le 2I
Tue Dec 02, 2014 9:58 pm
Forum: Naming
Topic: Knowing whether the compound has net neutral charge or not
Replies: 7
Views: 749

Re: Knowing whether the compound has net neutral charge or n

If the compound has a charge, it will say "ion" at the end in the name.
by Justin Le 2I
Tue Dec 02, 2014 9:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Writing equilibrium expression K
Replies: 2
Views: 329

Re: Writing equilibrium expression K

The textbook is merely introducing the concept of equilibria. Right now we are not working on aqueous equilibria, which is explored in Chapter 12 and that is the last chapter that we will be discussing this quarter.
by Justin Le 2I
Tue Dec 02, 2014 9:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep, Fall 2012 #8
Replies: 6
Views: 674

Re: Quiz 3 Prep, Fall 2012 #8

As long as at least one of the reactants or products is negative, then we automatically know that that x value is invalid. You don't need to waste time checking both reactants.
by Justin Le 2I
Tue Dec 02, 2014 9:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic Equations
Replies: 8
Views: 1170

Re: Cubic Equations

It is safe to say that x is negligible if K is smaller than 10-5.
by Justin Le 2I
Tue Dec 02, 2014 9:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: concentrations' effect on K
Replies: 3
Views: 319

Re: concentrations' effect on K

If you want to check if the reaction is favoring the reactants or the products, you would need to calculate a Q value with the new concentrations or pressures.
by Justin Le 2I
Tue Dec 02, 2014 9:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Preparation Fall 2013 Quiz: #10
Replies: 9
Views: 1363

Re: Quiz 3 Preparation Fall 2013 Quiz: #10

For determining the new partial pressure of BrCl in the new equilibrium mixture, I'm a unclear as to whether we are supposed to use the rxn given, 2BrCl --> Br2 + Cl2, or the reverse rxn, Br2 + Cl2 --> 2BrCl, since a NEW equilibrium is being established from the remaining pressures of the initial e...
by Justin Le 2I
Tue Dec 02, 2014 9:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep Fall 2012 #5
Replies: 3
Views: 434

Re: Quiz 3 Prep Fall 2012 #5

As the answer key says, H2^3 is only correct if you change the balanced equation so every stoichiometric equation is a whole number. So you would have to specify that in your answer if you use H2^3
by Justin Le 2I
Mon Dec 01, 2014 12:22 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate Question
Replies: 5
Views: 676

Re: Polydentate Question

For that problem, an easier way to get the answer is to count each instance of N, because N has an electron pair to donate. Because there are 3 N in that molecule, the molecule is tridentate.
by Justin Le 2I
Mon Nov 17, 2014 9:41 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Question 16.31
Replies: 1
Views: 245

Question 16.31

How do we determine if a molecule is monodentate or polydentate besides memorizing the different molecules? Is this property related to the geometry of the molecule or the charge on atoms?
by Justin Le 2I
Mon Nov 17, 2014 9:36 pm
Forum: Naming
Topic: H2O vs OH2
Replies: 2
Views: 2817

Re: H2O vs OH2

OH2 is preferred because that means the oxygen is binding to the central metal atom. Just a good tool to understand what is conceptually going on.
by Justin Le 2I
Tue Nov 11, 2014 3:26 pm
Forum: Lewis Structures
Topic: Which electrons (and orbitals) participate in bonding?
Replies: 3
Views: 1417

Re: Which electrons (and orbitals) participate in bonding?

Also remember that according to the valence bond theory, the 2s and 2p orbitals can be hybridized into, for example, sp3 where each of those orbitals have 1 valence electron.
by Justin Le 2I
Tue Nov 11, 2014 3:18 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 3
Views: 454

Re: Rydberg Equation

If you want to use the equation without the negative sign, remember that it has to be positive so n1 is smaller than n2.
by Justin Le 2I
Mon Nov 10, 2014 8:53 pm
Forum: Lewis Structures
Topic: Why does CH2 have a lone pair instead of two radicals?
Replies: 1
Views: 1265

Why does CH2 have a lone pair instead of two radicals?

CH2 has 6 electrons and four are used to bind C to the two H atoms. I thought that since the electron configuration of C has 2 unpaired electrons in two 2p orbitals, there would be two radicals and thus a tetrahedral shape. The solutions guide however says that there should be a trigonal planar shap...
by Justin Le 2I
Wed Nov 05, 2014 11:54 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: 2.77
Replies: 2
Views: 1024

Re: 2.77

The answer key says that KCl is the more soluble of the two choices in 2.77a.
by Justin Le 2I
Tue Nov 04, 2014 9:36 am
Forum: Dipole Moments
Topic: Dipole Moment Arrows
Replies: 5
Views: 1142

Re: Dipole Moment Arrows

For me personally, the old method for drawing dipole moment arrows is much clearer and understandable because there is a plus sign that is pointing towards the delta negative. If you still have questions, you can ask your TA.
by Justin Le 2I
Tue Nov 04, 2014 9:31 am
Forum: Bond Lengths & Energies
Topic: Chapter 2, #87
Replies: 1
Views: 374

Re: Chapter 2, #87

This is a solution manual error, the correction is on Lavelle's website.
by Justin Le 2I
Mon Nov 03, 2014 11:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electronegativity and Bond Angles
Replies: 1
Views: 795

Re: Electronegativity and Bond Angles

I think that only the lone pair repulsion will be on the quiz, like with the homework.
by Justin Le 2I
Mon Nov 03, 2014 11:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Radical (single electron) = region of e- density?
Replies: 2
Views: 582

Re: Radical (single electron) = region of e- density?

To add onto this question, OCLO on number 3.3b of the homework is also a trigonal planar molecule when there are four regions of electron density if the radical is included. I thought this was supposed to be tetrahedral because the book says a radical is counted as a region of electron density accor...
by Justin Le 2I
Mon Nov 03, 2014 11:38 pm
Forum: Electronegativity
Topic: Polarizing Power vs Polarizability
Replies: 2
Views: 12624

Re: Polarizing Power vs Polarizability

Figure 2.14 on page 79 of the text gives a good summary of the two concepts.
by Justin Le 2I
Mon Nov 03, 2014 11:31 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Octet Rules vs. Formal charge
Replies: 2
Views: 5388

Re: Octet Rules vs. Formal charge

Lewis structures that obey the octet rule are still correct, it is just that structures that have formal charges closer to zero are more stable.
by Justin Le 2I
Mon Nov 03, 2014 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair Doesn't change anything
Replies: 2
Views: 427

Re: Lone Pair Doesn't change anything

I noticed on the first question in chapter 3 hw that the linear structure "might" have lone pairs, however, is still a linear strucutre. Are there any example structures where the presence of lone pairs will not change the structure? In other words, is there a structure with lone pairs on...
by Justin Le 2I
Mon Nov 03, 2014 10:03 pm
Forum: Lewis Structures
Topic: Expanded octet question
Replies: 1
Views: 410

Re: Expanded octet question

I was working problem 2.55 in the textbook, sulfite had 1 structure with the octet rule and 3 that used the expanded octet rule. I understand that elements in the 3rd period and down can be expanded but i am confused as to how we know when to expand them or not? and how do I know that sulfer only s...
by Justin Le 2I
Mon Nov 03, 2014 10:00 pm
Forum: Lewis Structures
Topic: "most important" lewis structure
Replies: 1
Views: 346

Re: "most important" lewis structure

That question asks not only the most important structure, but also the equivalent resonance forms. That is why there are multiple answers but the one with the lowest formal charge is the most important.
by Justin Le 2I
Mon Nov 03, 2014 9:56 pm
Forum: Ionic & Covalent Bonds
Topic: Coordinate covalent bond
Replies: 2
Views: 1825

Re: Coordinate covalent bond

To add on to that, the boron atom doesn't have any more atoms to bond with so that is why it is stuck with 6 electrons. To get the full octet, a coordinate covalent bond must be formed where both electrons are donated by the F- anion.
by Justin Le 2I
Mon Nov 03, 2014 9:54 pm
Forum: Ionic & Covalent Bonds
Topic: Most likely charge for ions
Replies: 4
Views: 7658

Re: Most likely charge for ions

You can tell by the periodic table, just look at the group number.
by Justin Le 2I
Sat Nov 01, 2014 10:58 pm
Forum: Lewis Structures
Topic: Correct Lewis Structure for SO2?
Replies: 1
Views: 648

Correct Lewis Structure for SO2?

For this molecule, I have seen a model with two double bonds and a model with one double bond in the book and on the Internet. According to formal charge, the model with two double bonds is has lower energy but on problem 2.115d, the solutions uses the model with one double bond. Why would the model...
by Justin Le 2I
Wed Oct 22, 2014 4:48 pm
Forum: Trends in The Periodic Table
Topic: Trends in Atomic and Ionic Radius
Replies: 2
Views: 491

Re: Trends in Atomic and Ionic Radius

I noticed that too and I checked the document on the Chem 14A page that shows all the errors in the solutions and this problem was on it.
by Justin Le 2I
Tue Oct 21, 2014 10:35 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy Levels
Replies: 4
Views: 689

Re: Energy Levels

"n" is the principal quantum level. Each n value represents an orbital with a certain amount of energy. n=1 is closest to the nucleus, and as n increases the energy increases as well since you are getting further and further away from the nucleus. It takes more energy to excite an electro...
by Justin Le 2I
Tue Oct 21, 2014 10:31 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quiz 1 Preparation (2012) #8
Replies: 2
Views: 392

Re: Quiz 1 Preparation (2012) #8

In the section of the textbook where the Bohr Frequency Condition is discussed, there is an equation that has a denominator (n sub 2)^2 - (n sub 1)^2. So it is comparing the energy at two different shells and is labeling it the way Patrick said. The equation above just calculates the difference.
by Justin Le 2I
Tue Oct 21, 2014 10:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Spins
Replies: 5
Views: 732

Re: Electron Spins

I believe that having opposite spins within an orbital will keep the overall energy level lower, making the atom more stable.
by Justin Le 2I
Tue Oct 21, 2014 10:19 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Quiz 1 Preparation Fall 2012 Quiz
Replies: 2
Views: 428

Re: Quiz 1 Preparation Fall 2012 Quiz

The equal sign in the above post should actually be a greater than or equal to sign, but we just use equal to find the minimum uncertainty.
by Justin Le 2I
Mon Oct 20, 2014 4:42 pm
Forum: Properties of Light
Topic: Black Body Radiation
Replies: 2
Views: 415

Re: Black Body Radiation

The key thing to note about Figure 1.12 is that black bodies do not favor a wavelength when absorbing or emitting. That is why all the curves are a similar shape, it's just the temperature that is causing the overall energy density to increase.
by Justin Le 2I
Thu Oct 16, 2014 12:40 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Determining whether a given subshell can exist or not
Replies: 1
Views: 339

Re: Determining whether a given subshell can exist or not

Remember that for the subshells (s,p,d,f) they each are assigned an angular momentum quantum number which is signified by the symbol l. So for the s subshell, l =0, the p subshell, l=1 and so on. There is a handy table on page 26 of the text that summarizes this. So to answer your question, the subs...
by Justin Le 2I
Wed Oct 15, 2014 2:10 am
Forum: Photoelectric Effect
Topic: Energy to remove an electron
Replies: 3
Views: 471

Re: Energy to remove an electron

If there is no excess energy, then the electron is removed but it doesn't go anywhere and has no kinetic energy. Thus, the threshold energy and and the energy brought by the photon are equal.
by Justin Le 2I
Wed Oct 15, 2014 2:07 am
Forum: Photoelectric Effect
Topic: Hw 1.23
Replies: 3
Views: 996

Re: Hw 1.23

This is called the de Broglie relation by the way, and it's on the formula sheet.
by Justin Le 2I
Wed Oct 15, 2014 1:53 am
Forum: *Black Body Radiation
Topic: What is "black body radiation?"
Replies: 8
Views: 1096

Re: What is "black body radiation?"

I think we just need to know what black body radiation is and the Stefan-Boltzmann law which is Total intensity = constant x T^4. I would focus on problem 1.13 from the textbook.
by Justin Le 2I
Wed Oct 15, 2014 1:50 am
Forum: Einstein Equation
Topic: Planck's Constant
Replies: 2
Views: 483

Re: Planck's Constant

It's also important to remember two equations: E = h(frequency) and c=(wavelength)(frequency). You can combine these two equations because they share frequency and then you can solve for wavelength.
by Justin Le 2I
Wed Oct 15, 2014 1:40 am
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 116
Views: 10507

Re: All students read this sig fig post [ENDORSED]

I think we will because you can't get make up extra significant figures. We have to get our answer from what data is available to us.
by Justin Le 2I
Wed Oct 15, 2014 1:39 am
Forum: Significant Figures
Topic: Scientific Notation vs Decimal
Replies: 2
Views: 527

Re: Scientific Notation vs Decimal

Sometimes it will be easier to put the number in scientific notation so that it is easy to see how many significant figures there are and it is also easier to convert units, like from meters to millimeters.
by Justin Le 2I
Wed Oct 15, 2014 1:37 am
Forum: Balancing Chemical Reactions
Topic: Writing an Equation for the Reaction
Replies: 9
Views: 1758

Re: Writing an Equation for the Reaction

You can figure out the oxidation state by looking at your periodic table and noting the groups that boron and oxygen are in. Boron is in group 13, which typically has an oxidation state of +3. Aluminum is also +3. Oxygen is in group 16, or 2 groups from the end so it's oxidation state is -2.

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