Search found 30 matches

by Ellie Tsang 1I
Sun Jun 10, 2018 3:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar/nonpolar
Replies: 3
Views: 168

Re: polar/nonpolar

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.
by Ellie Tsang 1I
Sun Jun 10, 2018 3:51 pm
Forum: Calculating the pH of Salt Solutions
Topic: Calculating pH of a solution given molarity
Replies: 3
Views: 253

Re: Calculating pH of a solution given molarity

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.
by Ellie Tsang 1I
Fri Jun 08, 2018 2:08 pm
Forum: Sigma & Pi Bonds
Topic: Molecular orbital energy-level diagram
Replies: 1
Views: 139

Molecular orbital energy-level diagram

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?
by Ellie Tsang 1I
Mon Jun 04, 2018 7:32 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation number
Replies: 4
Views: 167

Re: Oxidation number

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.
by Ellie Tsang 1I
Mon Jun 04, 2018 7:29 am
Forum: Lewis Structures
Topic: Central Atom(s)
Replies: 6
Views: 215

Re: Central Atom(s)

The central atom in a Lewis Structure is usually the least electronegative atom, with the exception to hydrogen:
by Ellie Tsang 1I
Mon Jun 04, 2018 7:28 am
Forum: Hybridization
Topic: Sigma Bonds
Replies: 5
Views: 180

Re: Sigma Bonds

Sigma bonds are important because they can rotate. This is also why single bonds are weaker than double bonds.
by Ellie Tsang 1I
Tue May 29, 2018 11:23 am
Forum: Ionic & Covalent Bonds
Topic: Double/Triple Bonds
Replies: 8
Views: 321

Re: Double/Triple Bonds

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.
by Ellie Tsang 1I
Thu May 24, 2018 11:22 am
Forum: Ionic & Covalent Bonds
Topic: Ionic and Covalent Bonds
Replies: 2
Views: 191

Re: Ionic and Covalent Bonds

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...
by Ellie Tsang 1I
Thu May 24, 2018 9:54 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power
Replies: 3
Views: 208

Re: Polarizing Power

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.
by Ellie Tsang 1I
Sat May 19, 2018 11:17 pm
Forum: Lewis Structures
Topic: Charge on Molecule [ENDORSED]
Replies: 4
Views: 176

Re: Charge on Molecule [ENDORSED]

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.
by Ellie Tsang 1I
Sat May 19, 2018 11:11 pm
Forum: Dipole Moments
Topic: Dipole relevance
Replies: 4
Views: 139

Re: Dipole relevance

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...
by Ellie Tsang 1I
Sat May 19, 2018 11:02 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic bonds
Replies: 6
Views: 236

Re: Ionic bonds

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.
by Ellie Tsang 1I
Sun May 13, 2018 2:53 pm
Forum: Lewis Structures
Topic: Most Important Lewis Structure
Replies: 4
Views: 176

Re: Most Important Lewis Structure

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.
by Ellie Tsang 1I
Sun May 13, 2018 2:50 pm
Forum: Lewis Structures
Topic: formal charge?
Replies: 3
Views: 604

Re: formal charge?

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.
by Ellie Tsang 1I
Wed May 09, 2018 5:15 pm
Forum: Photoelectric Effect
Topic: Kinetic Energy
Replies: 2
Views: 173

Kinetic Energy

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...
by Ellie Tsang 1I
Sun May 06, 2018 12:43 am
Forum: Molarity, Solutions, Dilutions
Topic: Test 1, Q1
Replies: 2
Views: 224

Re: Test 1, Q1

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...
by Ellie Tsang 1I
Sun May 06, 2018 12:35 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations Exceptions
Replies: 3
Views: 89

Re: Electron Configurations Exceptions

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.
by Ellie Tsang 1I
Wed May 02, 2018 12:10 am
Forum: Quantum Numbers and The H-Atom
Topic: Principle quantum number and orbital angular momentum quantum number
Replies: 2
Views: 121

Principle quantum number and orbital angular momentum quantum number

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?
by Ellie Tsang 1I
Sun Apr 29, 2018 9:44 am
Forum: *Shrodinger Equation
Topic: Shrodinger Equation
Replies: 7
Views: 328

Re: Shrodinger Equation

To add on, there can be multiple solutions depending on how many orbitals there are.
by Ellie Tsang 1I
Sat Apr 28, 2018 9:20 am
Forum: *Shrodinger Equation
Topic: Schrodinger Equation [ENDORSED]
Replies: 8
Views: 422

Re: Schrodinger Equation [ENDORSED]

En is the energy at some orbital, n.
by Ellie Tsang 1I
Sat Apr 28, 2018 9:13 am
Forum: Photoelectric Effect
Topic: Longest and Highest Wavelength of Radiation that is able to eject an electron [ENDORSED]
Replies: 2
Views: 133

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

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!
by Ellie Tsang 1I
Sat Apr 21, 2018 4:38 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Finding the Energy of A Photon
Replies: 3
Views: 139

Re: Finding the Energy of A Photon

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 .
by Ellie Tsang 1I
Sat Apr 21, 2018 4:32 pm
Forum: DeBroglie Equation
Topic: equations that apply to light only/everything else but light
Replies: 8
Views: 310

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

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.
by Ellie Tsang 1I
Sat Apr 21, 2018 4:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Equation significance
Replies: 4
Views: 124

Re: Uncertainty Equation significance

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.
by Ellie Tsang 1I
Sat Apr 14, 2018 10:52 pm
Forum: Molarity, Solutions, Dilutions
Topic: Percentage of Solution Molarity Problem
Replies: 1
Views: 531

Re: Percentage of Solution Molarity Problem

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.
by Ellie Tsang 1I
Sat Apr 14, 2018 10:42 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Electron Energy Levels
Replies: 3
Views: 128

Re: Electron Energy Levels

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.
by Ellie Tsang 1I
Sat Apr 14, 2018 10:36 pm
Forum: General Science Questions
Topic: Energy (photon) - Energy (remove e-???) [ENDORSED]
Replies: 4
Views: 464

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

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.
by Ellie Tsang 1I
Sat Apr 07, 2018 10:12 pm
Forum: Balancing Chemical Reactions
Topic: Using the algebraic method on chemical equations that involve OH groups, etc. [ENDORSED]
Replies: 1
Views: 94

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

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.
by Ellie Tsang 1I
Fri Apr 06, 2018 3:24 pm
Forum: Limiting Reactant Calculations
Topic: M.5
Replies: 4
Views: 164

Re: M.5

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.
by Ellie Tsang 1I
Fri Apr 06, 2018 2:18 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Percent composition [ENDORSED]
Replies: 3
Views: 154

Re: Percent composition [ENDORSED]

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...

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