## Search found 142 matches

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.
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.
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.
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.
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.
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.
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.
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...
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
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.
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?
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.
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.
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.
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...
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.
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.
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.
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.
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...
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.
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.
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...
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...
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.
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.
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.
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...
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.
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...
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.
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.
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.
Mon Oct 20, 2014 4:42 pm
Forum: Properties of Light
Replies: 2
Views: 415

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.
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...
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.
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.
Wed Oct 15, 2014 1:53 am
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.
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.
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.
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.
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.