CHEMISTRY COMMUNITY

Ellie Tsang 1I

A polar molecule is a molecule that has a nonzero dipole moment, while a nonpolar molecule is a molecule that has no dipole moment. That means in polar molecules, the forces do not cancel out. Instead, the forces will cancel out for nonpolar molecules.

Ellie Tsang 1I

You have to write out the balanced equation for Na2O and H2O first, and you will find that 2Na+ + O2- + H2O --> 2Na+ + 2OH-. Convert the molarity of Na2O into moles and find out how many moles of OH- you get. Then covert moles of OH- to molarity and take the -log of that to get the pOH.

Ellie Tsang 1I

I understand what sigma and pi bonds are, but what exactly does the * mean in σ* and π*? How do you know when you have them?

Ellie Tsang 1I

The sum of oxidation numbers for a neutral compound is 0 and the sum of oxidation numbers for a polyatomic compound is the charge of the ion. By knowing specific charges for atoms (e.g. Hydrogen has a charge of +1), you can do basic algebra to solve for the charges of the other atoms.

Ellie Tsang 1I

The central atom in a Lewis Structure is usually the least electronegative atom, with the exception to hydrogen:

Ellie Tsang 1I

Sigma bonds are important because they can rotate. This is also why single bonds are weaker than double bonds.

Ellie Tsang 1I

You use double/triple bonds to fulfill the octet rule. So, if 2 atoms do not have 8 valence electrons yet, and they both have an unbonded electron, you can form a double/triple bond between them.

Ellie Tsang 1I

In ionic bonds, electrons are not shared; instead, they are transferred from the less electronegative atom to the more electronegative atom. In covalent bonds, electrons are shared and the difference in charges is due to one atom being more electronegative than the other-the more electronegative ato...

Ellie Tsang 1I

When determining which cations have higher polarizing power, first consider the charge. A cation with a higher charge will have higher polarizing power. If charges are the same, consider the size. Smaller cations will have higher polarizing power.

Ellie Tsang 1I

Andrew is right in that you calculate the formal charge. Another easier way to see this is if the atom has more or less valence electrons than it should have.

Ellie Tsang 1I

So what's the difference between a dipole and polar molecule? Isn't water also polar? Dipole-dipole interactions are a type intermolecular forces (between molecules) while polar covalent bonds are a type of intramolecular force (within a molecule). Water contains both dipole-dipole interactions and...

Ellie Tsang 1I

Cameron Smith 1I wrote:When do we place brackets around ions?

Brackets are used for all Lewis structures for ions because it shows the net charge.

Ellie Tsang 1I

Yes, you do want the most stable Lewis Structure, but you should consider things like fulfilling the octet rule and ensuring that each element's formal charge is as close to 0 as possible. I think double bonds would be related to the sharing of electrons and fulfilling the octet rule.

Ellie Tsang 1I

Formal charge also helps when you are drawing Lewis Structures because you want all of the formal charges for each element to be as close to 0 as possible.

Ellie Tsang 1I

In the textbook, it says "The kinetic energy of the electron ejected from the metal increases linearly with the frequency of the incident radiation according to Eq. 5." Why doesn't a higher frequency light emit electrons with higher kinetic energies? This is from Worksheet 3 - Quantum Worl...

Ellie Tsang 1I

Use the equation M=mol/L to determine how many moles of KCl there are, which is 0.100 mol KCl. In 1 mole of KCl, there is 1 mole of Cl-, so there are 0.100 mol Cl-. Because the question asks for the concentration of Cl- after the dilution, take your answer from part a (0.185 mol Cl-) and add it to 0...

Ellie Tsang 1I

Just remember that a subshell is more stable if it is half full or full. Thus, 3d^4 becomes 3d^5 and 3d^9 becomes 3d^10.

Ellie Tsang 1I

In the textbook, it says that l = 0,1,2,..., n - 1. For question 2.27, n = 5 and l =2. I don’t understand how l can equal 2. Can someone clarify?

Ellie Tsang 1I

To add on, there can be multiple solutions depending on how many orbitals there are.

Ellie Tsang 1I

En is the energy at some orbital, n.

Ellie Tsang 1I

To calculate the longest wavelength, which means the minimum energy required to eject an electron, set the work equation to E=hv. I’m not sure if you can actually solve for the shortest wavelength since you just need to get past the longest wavelength, but if anyone could clarify, that’d be great!

Ellie Tsang 1I

If you remember the equations like E=hv and c=λv, you can manipulate the energy equation to find the energy of a photon. For example, E is also equal to hc/λ .

Ellie Tsang 1I

I'm confused about that too. I read that light doesn't have mass because it's made up of photons, which is massless and only energy and momentum. The momentum equation involves mass, so I don't get how a photon is massless.

Ellie Tsang 1I

One significant thing about the Heisenberg Uncertainty Principle we learned in lecture Friday is that it tells us that atoms have a physical limit to the minimum size that atoms can exist.

Ellie Tsang 1I

Take 12% of the 750-mL of wine. Then you set 0.789 g/mL = X/90 mL, and after, convert X into moles using the molar mass of ethanol. You should get 1.5 moles.

Ellie Tsang 1I

The electrons in n=4 is further away from the nucleus as compared to n=2, so the force between the nucleus and the electron is smaller. This means it requires less energy to remove the electrons, and this corresponds to the energy level of it.

Ellie Tsang 1I

From what I understand, the piece of metal is not putting in energy to remove the electrons, but the light striking the metal. The light must have enough energy (so a short enough wavelength) for electrons to be ejected.

Ellie Tsang 1I

You would multiply the 2 attached to the PO4 because the algebraic method takes into account the amount of atoms of each element on the reactants and products side.

Ellie Tsang 1I

In general, just use the mass of the limiting reactant to determine how much of the excess reactant will be produced. Then subtract how much of the excess reactant there was in the beginning of the reaction by how much of the excess reactant was produced.

Ellie Tsang 1I

You calculate percent composition when the question gives you the masses of each element that makes up the sample. The percent composition is then the mass of the element out of 100(in grams). Then convert the masses to moles, divide them by the smallest mole amount, multiply them so they’re whole n...

CHEMISTRY COMMUNITY

Search found 30 matches

Re: polar/nonpolar

Re: Calculating pH of a solution given molarity

Molecular orbital energy-level diagram

Re: Oxidation number

Re: Central Atom(s)

Re: Sigma Bonds

Re: Double/Triple Bonds

Re: Ionic and Covalent Bonds

Re: Polarizing Power

Re: Charge on Molecule [ENDORSED]

Re: Dipole relevance

Re: Ionic bonds

Re: Most Important Lewis Structure

Re: formal charge?

Kinetic Energy

Re: Test 1, Q1

Re: Electron Configurations Exceptions

Principle quantum number and orbital angular momentum quantum number

Re: Shrodinger Equation

Re: Schrodinger Equation [ENDORSED]

Re: Longest and Highest Wavelength of Radiation that is able to eject an electron [ENDORSED]

Re: Finding the Energy of A Photon

Re: equations that apply to light only/everything else but light

Re: Uncertainty Equation significance

Re: Percentage of Solution Molarity Problem

Re: Electron Energy Levels

Re: Energy (photon) - Energy (remove e-???) [ENDORSED]

Re: Using the algebraic method on chemical equations that involve OH groups, etc. [ENDORSED]

Re: M.5

Re: Percent composition [ENDORSED]