Search found 30 matches

by Haorui Li 1A
Sun Jul 28, 2019 9:06 pm
Forum: Amphoteric Compounds
Topic: pH of Amphoteric Compounds
Replies: 3
Views: 75

Re: pH of Amphoteric Compounds

What will the question be like if we have Amphoteric Compounds questions on final?
by Haorui Li 1A
Sun Jul 28, 2019 8:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Geometry vs molecular shape
Replies: 5
Views: 77

Re: Geometry vs molecular shape

When no lone pairs of electrons are present, the electronic geometry is the same as the molecular shape. Things are different when a lone pair is presented. Different molecules with the same geometry shape can have different molecular shapes depend on the number of their lone pairs.
by Haorui Li 1A
Sun Jul 28, 2019 8:18 pm
Forum: Sigma & Pi Bonds
Topic: Sigma/pi bonds
Replies: 3
Views: 110

Re: Sigma/pi bonds

Can Pi bonds be considered just a force of attraction between electron pairs?
by Haorui Li 1A
Sun Jul 28, 2019 8:11 pm
Forum: Hybridization
Topic: Hybridizing orbitals [ENDORSED]
Replies: 1
Views: 66

Re: Hybridizing orbitals [ENDORSED]

To form bonds, CH4, for example, the central Carbon needs to form 4 bonds with 4 H to form one CH4 molecule. Thus, there are 4 regions of electron density around the C, so we know that C is sp3 hybridized.
by Haorui Li 1A
Sun Jul 28, 2019 7:51 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Nitrogen as a Base
Replies: 6
Views: 145

Re: Nitrogen as a Base

The electron pairs donor is considered to be Lewis base, an N with a lone pair is able to donate its lone pair and form bonds, so it is considered a Lweis base.
by Haorui Li 1A
Sun Jul 28, 2019 7:45 pm
Forum: Ionic & Covalent Bonds
Topic: Back and Fourth Arrows
Replies: 3
Views: 81

Re: Back and Fourth Arrows

Two-way double half arrows represent a reaction that can go either forward or reverse. Whether the reaction shifts or not depends on Le Chatlier's principle. In the lecture, strong acids used double arrows but weak acids used single arrows.
by Haorui Li 1A
Sun Jul 28, 2019 7:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: question 4.19
Replies: 2
Views: 85

Re: question 4.19

I think the Lewis structure of (CH3)2 Be should be linear. Beryllium would be the central atom, and it forms two bonds, one to each Carbon of the CH3. Each Carbon is bonded to Beryllium and to 3 hydrogens so it has 4 bonds.
by Haorui Li 1A
Sun Jul 21, 2019 2:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hybridization
Replies: 2
Views: 112

Hybridization

Can someone explain why is BeCl2 sp hybridized? Why are there only 4 electrons around Be in the Lewis structure?
by Haorui Li 1A
Sun Jul 21, 2019 2:09 pm
Forum: Lewis Structures
Topic: Complete Lewis Structure [ENDORSED]
Replies: 6
Views: 260

Re: Complete Lewis Structure [ENDORSED]

The formal charge is just a way for you to rearrange the position of each element in the Lewis structure, meaning by applying formal charge, you can find the relative most stable structure. Partial charge is for you to see if the molecule is polar. It is represented by the Greek lowercase letter δ, ...
by Haorui Li 1A
Sun Jul 21, 2019 2:03 pm
Forum: Ionic & Covalent Bonds
Topic: Dipoles
Replies: 7
Views: 246

Re: Dipoles

Dipoles are usually polar, but I think the VSEPR shapes determine if the dipoles can cancel out. If the dipoles can be canceled out, for example, tetrahedral, then the molecule will not be polar.
by Haorui Li 1A
Sun Jul 21, 2019 1:58 pm
Forum: Ionic & Covalent Bonds
Topic: Inter and Intra
Replies: 8
Views: 228

Re: Inter and Intra

Intramolecular forces are the forces that hold atoms together within a molecule. There are 3 types of intramolecular bonds: covalent, ionic, and metallic. Intermolecular forces are forces that exist between molecules. Key intermolecular forces are as follows: Hydrogen bonding > Van der Waals dipole-...
by Haorui Li 1A
Sun Jul 21, 2019 1:54 pm
Forum: Empirical & Molecular Formulas
Topic: Formulas
Replies: 4
Views: 348

Re: Formulas

After you get the empirical formula, you get the molar mass of the empirical formula of the compound. If you need to find the molecular formula, the question will give you the molar mass of the molecular formula. Now you divide the molar mass of the molecular formula by the molar mass of the empiric...
by Haorui Li 1A
Sun Jul 14, 2019 2:28 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Which do you prioritize first
Replies: 10
Views: 263

Re: Which do you prioritize first

I think the formal charge is just a way to provide you a possible more stable Lewis structure.
by Haorui Li 1A
Sun Jul 14, 2019 2:26 pm
Forum: Ionic & Covalent Bonds
Topic: Ion-Dipole
Replies: 3
Views: 270

Re: Ion-Dipole

Ion-dipole forces can be generated between polar water molecules and a sodium ion. The oxygen atom in the water molecule has a slight negative charge and is attracted to the positive sodium ion. These intermolecular ion-dipole forces are much weaker than covalent or ionic bonds.
by Haorui Li 1A
Sun Jul 14, 2019 2:23 pm
Forum: Bond Lengths & Energies
Topic: Intermolecular vs. Intramolecular forces
Replies: 5
Views: 180

Re: Intermolecular vs. Intramolecular forces

Intramolecular forces are the forces that hold atoms together within a molecule. There are 3 types of intramolecular bonds: covalent, ionic, and metallic. Intermolecular forces are forces that exist between molecules. The four key intermolecular forces are as follows: Ionic bonds > Hydrogen bonding ...
by Haorui Li 1A
Sun Jul 14, 2019 2:19 pm
Forum: Lewis Structures
Topic: Aluminum and Boron [ENDORSED]
Replies: 2
Views: 150

Aluminum and Boron [ENDORSED]

I learned this in high school, but can someone explain why when we draw the Lewis structures, Aluminum and Boron have only 6 electrons around them and they satisfy the octet rule?
by Haorui Li 1A
Sun Jul 14, 2019 2:15 pm
Forum: Octet Exceptions
Topic: Expanded octet
Replies: 3
Views: 161

Re: Expanded octet

The octet rule can be ‘expanded’ by some elements by utilizing the d- orbitals found in the third principal energy level and beyond. For the elements in the second period of the periodic table (principal energy level n=2), the s2p6 electrons comprise the octet, and no d sublevel exists. As a result,...
by Haorui Li 1A
Sun Jul 14, 2019 2:08 pm
Forum: Bond Lengths & Energies
Topic: Electrostatic Potential Energy Formula
Replies: 2
Views: 112

Re: Electrostatic Potential Energy Formula

The magnitude of the electric force between q1 and q2 is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance between them. This equation is known as Coulomb’s Law.
by Haorui Li 1A
Sat Jul 06, 2019 2:58 pm
Forum: Properties of Light
Topic: wavelength
Replies: 11
Views: 503

Re: wavelength

The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. The amplitude can be measured from the rest position to the trough position.
by Haorui Li 1A
Sat Jul 06, 2019 2:55 pm
Forum: Limiting Reactant Calculations
Topic: 4b on Test 1
Replies: 2
Views: 220

Re: 4b on Test 1

Here is how I answered it. Hope it helps.
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by Haorui Li 1A
Sat Jul 06, 2019 2:48 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Equations
Replies: 4
Views: 282

Re: Balancing Equations

In this question, it asks "What is the net number of moles of gas produced?", so we look at compounds that are in the gas phase. In the chemical equation, all compounds are in the gas phase, so to calculate the net number, we just calculate the net change from reactants to products. If the...
by Haorui Li 1A
Sat Jul 06, 2019 2:36 pm
Forum: Balancing Chemical Reactions
Topic: balancing reaction law
Replies: 2
Views: 164

Re: balancing reaction law

You cannot add a product to the chemical equation because a chemical equation describes a chemical reaction, it is an expression that gives the identities and quantities of the substances involved in a reaction, if the product was not there originally, you cannot add one. Balancing chemical equation...
by Haorui Li 1A
Sat Jul 06, 2019 2:29 pm
Forum: Significant Figures
Topic: Determining sig figs
Replies: 10
Views: 373

Re: Determining sig figs

I think if we don't have the correct sig. fig. the points will be deducted even if you have correct answers.
by Haorui Li 1A
Mon Jul 01, 2019 1:53 pm
Forum: Balancing Chemical Reactions
Topic: Elemental states [ENDORSED]
Replies: 6
Views: 250

Re: Elemental states [ENDORSED]

(aq) means aqueous solutions, which means the solvent of the solution is water. It depends on the statement in the question, but I believe for most solutions we use (aq) (e.g. NaOH(aq) and HCL(aq) ), and H2O should be (l).
by Haorui Li 1A
Fri Jun 28, 2019 7:09 pm
Forum: Limiting Reactant Calculations
Topic: How to distinguish limiting or excess reactant.
Replies: 4
Views: 164

Re: How to distinguish limiting or excess reactant.

Since the chemical equation is balanced, we can see 1 mole of C reacts with 1 mole of O2 to form 1 mole of CO2. The ratio to carbon, oxygen and carbon dioxide are 1:1:1, so if there are 1mol carbon atoms and 1mol oxygen molecules, 1 mol of CO2 will be formed so there will be no limiting reactant. Ho...
by Haorui Li 1A
Thu Jun 27, 2019 11:17 am
Forum: Empirical & Molecular Formulas
Topic: Molar Mass vs. Atomic Weight
Replies: 7
Views: 286

Re: Molar Mass vs. Atomic Weight

The unit for atomic mass is in amu, however, the unit for molar mass is g/mol.
by Haorui Li 1A
Thu Jun 27, 2019 10:39 am
Forum: Empirical & Molecular Formulas
Topic: How to determine the order of elements? [ENDORSED]
Replies: 1
Views: 117

How to determine the order of elements? [ENDORSED]

In the discussion 1A, we solved a practice problem about the empirical formula and molecular formula, I just want to know how do we determine the order of the element in a compound if there are 3 or more. For example, the question that we did in class was about Os, O and C. The answer was OsC4O4, I ...
by Haorui Li 1A
Wed Jun 26, 2019 9:51 pm
Forum: SI Units, Unit Conversions
Topic: Can someone explain why we use kg for mass as the base unit?
Replies: 4
Views: 170

Re: Can someone explain why we use kg for mass as the base unit?

I believe Dr.Lavelle said since the molar mass is always in grams per mole, we tend to use grams in questions and the grams tend to cancel out each other. Can someone explain more?
by Haorui Li 1A
Wed Jun 26, 2019 9:33 pm
Forum: Properties of Light
Topic: Light variables
Replies: 3
Views: 163

Re: Light variables

Properties of Light: 1.Wavelength(λ) a. Distance between two consecutive peaks or troughs in a wave b. Measured in meters (SI system) 2. Frequency(ν) a. The number of waves that pass a given point per second b. Measured in hertz (sec-1) 1Hz=1 (1/s) 3. Speed(c) a. Measured in meters/sec b. Speed in V...
by Haorui Li 1A
Wed Jun 26, 2019 9:24 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Theoretical/Actual Yield
Replies: 6
Views: 172

Theoretical/Actual Yield

What is the unit for theoretical yield or actual yield? In the example Dr. Lavelle provided in class the unit was in grams, does it always need to be in grams or based on different questions the unit changes?

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