Search found 101 matches

by Charisse Vu 1H
Sun Mar 15, 2020 1:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic and voltaic cells
Replies: 5
Views: 68

Re: Galvanic and voltaic cells

Galvanic and voltaic cells are the same.
by Charisse Vu 1H
Sun Mar 15, 2020 1:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: calculating standard cell potential
Replies: 6
Views: 66

Re: calculating standard cell potential

You would take take the standard potential of the cathode and subtract the standard potential of the anode from it.
by Charisse Vu 1H
Sun Mar 15, 2020 1:34 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: heterogeneous vs homogeneous catalysts
Replies: 2
Views: 39

Re: heterogeneous vs homogeneous catalysts

I don't think knowing the difference is too significant to this course and the final. I think it is just good to know that there are different kinds of catalysts.
by Charisse Vu 1H
Sun Mar 15, 2020 1:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem Final Typo
Replies: 8
Views: 249

Re: Chem Final Typo

I felt that there was a typo, but maybe it was just Professor Lavelle's way of making sure we pay attention to the answers.
by Charisse Vu 1H
Sun Mar 15, 2020 1:31 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Graphs
Replies: 3
Views: 55

Re: Graphs

The graphs only show order in relation to a specific molecule/reactant. I do not believe we know the graphs for overall orders.
by Charisse Vu 1H
Sun Mar 08, 2020 11:26 pm
Forum: First Order Reactions
Topic: Half Life
Replies: 13
Views: 101

Half Life

Why do we need to know how to calculate half lives? In what context would a half life question be given?
by Charisse Vu 1H
Sun Mar 08, 2020 11:23 pm
Forum: Second Order Reactions
Topic: Derivation of the Equation
Replies: 2
Views: 10

Derivation of the Equation

Do we need to know how to derive the equation? I know that Professor Lavelle went over it in class, but I am not sure if we have to know how to derive it for the final.
by Charisse Vu 1H
Sun Mar 08, 2020 11:22 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Pre-Equilibrium
Replies: 3
Views: 30

Pre-Equilibrium

Why do we use the pre-equilbrium approach instead of the other methods presented in class?
by Charisse Vu 1H
Sun Mar 08, 2020 11:20 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Relationship between Equilibrium Constant and Rate Constants
Replies: 1
Views: 15

Relationship between Equilibrium Constant and Rate Constants

How are equilibrium constants and rate constants related? I understand there is an equation relating them, but I would like a conceptual explanation as to how they are related.
by Charisse Vu 1H
Sun Mar 08, 2020 11:17 pm
Forum: Zero Order Reactions
Topic: Order of Reaction
Replies: 3
Views: 28

Order of Reaction

How do you determine if a reaction is zero, first, or second order? Is there a way to tell without looking at a graph?
by Charisse Vu 1H
Sun Mar 01, 2020 11:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Difference Between Galvanic and Voltaic Cells
Replies: 3
Views: 17

Difference Between Galvanic and Voltaic Cells

Is there a difference between galvanic and voltaic cells? Or are they just two names given to the same thing?
by Charisse Vu 1H
Sun Mar 01, 2020 11:27 pm
Forum: Balancing Redox Reactions
Topic: Writing Half-reactions
Replies: 1
Views: 29

Re: Writing Half-reactions

I think that conventionally, you always add things together rather than subtracting them. Zn is being broken down into 2 electrons and Zn2+. Although it does seem clearer to subtract the electrons because it lost them, I would just stick with adding 2 electrons to Zn2+ to keep things consistent.
by Charisse Vu 1H
Sun Mar 01, 2020 11:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive force
Replies: 3
Views: 29

Re: Electromotive force

Electromotive force is simply the potential difference between two cells. Electron flow can go in any direction, depending on which side has the cathode/anode. But, it is typically calculated cathode-anode (right minus left).
by Charisse Vu 1H
Sun Mar 01, 2020 11:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells and pH
Replies: 1
Views: 31

Re: Galvanic Cells and pH

I believe that it only matters when H+ or OH- are involved in the reaction (when you are using the Nernst equation).
by Charisse Vu 1H
Sun Mar 01, 2020 11:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Notation
Replies: 4
Views: 38

Re: Cell Notation

Since it is a solvent, you don't need to put it in the cell diagram.
by Charisse Vu 1H
Sat Feb 22, 2020 5:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potentials
Replies: 4
Views: 30

Re: Standard Cell Potentials

Professor Lavelle says to do right minus left, because conventionally, the cathode is written on the right and the anode is written on the left. However, it should always be cathode-anode.
by Charisse Vu 1H
Sat Feb 22, 2020 4:59 pm
Forum: Balancing Redox Reactions
Topic: Hw problem 6k.5 b)
Replies: 2
Views: 21

Re: Hw problem 6k.5 b)

I believe that you would assume that it is both an oxidizing and reducing agent. You should still split the reaction into 2 half reactions. Br2 --> Br- is the reduction reaction (0 to 1-) and Br2 --> BrO3- is the oxidation reaction (0 to 5+).
by Charisse Vu 1H
Sat Feb 22, 2020 4:48 pm
Forum: Balancing Redox Reactions
Topic: Cell Diagrams
Replies: 5
Views: 78

Re: Cell Diagrams

Yes, Professor Lavelle said during lecture that when there are no conducting solids given in the problem (both the reactant and product are in solution), use Platinum as the electrode. He also said graphite works too but platinum is more common.
by Charisse Vu 1H
Sat Feb 22, 2020 4:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: max potential in Galvanic Cell
Replies: 4
Views: 27

Re: max potential in Galvanic Cell

But why is it that the maximum potential of the cell is when the switch is closed (very little current flowing)? What exactly does "maximum potential" mean?
by Charisse Vu 1H
Sun Feb 16, 2020 11:31 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: ΔS for Irreversible Expansion
Replies: 3
Views: 47

Re: ΔS for Irreversible Expansion

In the book, example 4I.3 explains this concept very well! I would go through that example and read some of the information in that section, as I believe the book explains delta S in more depth than what we covered in class.
by Charisse Vu 1H
Sun Feb 16, 2020 11:29 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Number Rules
Replies: 7
Views: 62

Oxidation Number Rules

Do we have to memorize the oxidation number rules?
by Charisse Vu 1H
Sun Feb 16, 2020 11:21 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 3
Views: 46

Van't Hoff Equation

Can someone go over how the van't hoff equation was derived from delta g and how K plays a role in the equation? Thanks!
by Charisse Vu 1H
Sun Feb 16, 2020 11:17 pm
Forum: Van't Hoff Equation
Topic: Assumptions
Replies: 3
Views: 43

Re: Assumptions

We always assume that delta S is the same at different temperatures because we can assume that the difference in delta S between the reactants and products is the same at two different temperatures.
by Charisse Vu 1H
Sun Feb 16, 2020 11:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Spectator Ions
Replies: 3
Views: 38

Spectator Ions

Do we include spectator ions in the equilibrium constant?
by Charisse Vu 1H
Sat Feb 08, 2020 3:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Using Cv,m and Cp,m
Replies: 2
Views: 28

Using Cv,m and Cp,m

When do we use Cv,m and Cp,m? Also, why and when do we use 5R/2, 3R/2, etc.? I am kind of confused on this, as I don't recall Professor Lavelle really explaining it.
by Charisse Vu 1H
Sat Feb 08, 2020 3:10 pm
Forum: Phase Changes & Related Calculations
Topic: Steam burns more than water
Replies: 5
Views: 67

Re: Steam burns more than water

Steam at 100C causes a worse burn than water at 100C because steam at 100C has a lot more energy than boiling water at the same temperature. If you recall the phase change graph, a lot of energy is put into vaporizing water into a gas. During a phase change, the temperature remains constant, but the...
by Charisse Vu 1H
Sat Feb 08, 2020 3:06 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4B.3
Replies: 1
Views: 34

4B.3

4B.3: The internal energy of a system increased by 982 J when it was supplied with 492 J of energy as heat. (a) Was work done by or on the system? (b) How much work was done? I understand that work was done on the system for the internal energy to be increased by 982 J, but I don't understand why th...
by Charisse Vu 1H
Sat Feb 08, 2020 2:59 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy equations
Replies: 2
Views: 33

Re: Entropy equations

You can find a list of all the formulas and constants on the cover page of the first test we took. It has most of the formulas needed, but depending on the question, you may need to know how to manipulate equations to solve the question.
by Charisse Vu 1H
Sat Feb 08, 2020 2:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.13
Replies: 2
Views: 43

Re: 4A.13

Since the calorimeter contains the same volume of liquid in both cases (0.200 L and 100.0 mL+100.0 mL), there is no change in volume and the final volume is constant at 0.100 L. That is why the volumes are not considered since there is no change in volume.
by Charisse Vu 1H
Sat Feb 08, 2020 2:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U at Constant V/P
Replies: 4
Views: 41

Re: Delta U at Constant V/P

At constant volume, delta u = q because there is no work being done. Work requires that there is a change in volume, as the book defines work as "the process of achieving motion against an opposing force". At constant pressure, delta u = q - P*delta V because you can rearrange the equation...
by Charisse Vu 1H
Wed Jan 29, 2020 10:34 am
Forum: Ideal Gases
Topic: ideal gases
Replies: 13
Views: 215

Re: ideal gases

An ideal gas is a theoretical gas that does not have any intermolecular attractive forces, does not take up space, and obeys the ideal gas law.
by Charisse Vu 1H
Wed Jan 29, 2020 10:30 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: approximation
Replies: 4
Views: 44

Re: approximation

You can approximate x to be 0 when the Ka/Kb value is less than 10^-3. However, you also need to check that the x value you calculate is less than 5% of the initial amount.
by Charisse Vu 1H
Wed Jan 29, 2020 10:29 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Bomb Calorimetry
Replies: 2
Views: 20

Re: Bomb Calorimetry

The bomb calorimeter is a constant volume calorimeter that is used to measure the heat of combustion of a reaction.
by Charisse Vu 1H
Wed Jan 29, 2020 10:27 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Bomb calorimeter
Replies: 2
Views: 23

Re: Bomb calorimeter

A bomb calorimeter is a constant volume calorimeter. The reason why it is called a bomb calorimeter is because there is a large increase in pressure when a reaction occurs in the bomb vessel.
by Charisse Vu 1H
Wed Jan 29, 2020 10:02 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework for Week 4
Replies: 2
Views: 34

Homework for Week 4

I am a bit confused on which homework problems we should be doing for this week. It seems like the homework problems that we could do are all over the place (some in 4A, 4C, 4D). Are these the sections we should be doing problems from or am I missing something?
by Charisse Vu 1H
Sun Jan 26, 2020 11:54 pm
Forum: Phase Changes & Related Calculations
Topic: Chem 14A Final Pickup
Replies: 8
Views: 62

Re: Chem 14A Final Pickup

I have picked up the final, but I am unsure if they will still be available this week because Professor Lavelle's email said that they would be available during week 3.
by Charisse Vu 1H
Sun Jan 26, 2020 11:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Methods to Calculate Enthalpies
Replies: 6
Views: 51

Methods to Calculate Enthalpies

How do we know which method to use when calculating the total enthalpy of a reaction?
by Charisse Vu 1H
Sun Jan 26, 2020 11:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method of calculating
Replies: 3
Views: 23

Re: Method of calculating

I believe using the standard reaction enthalpies would give you the most accurate answers. In the slides, it stated that if bond enthalpies are not available, then standard reaction enthalpies should be used.
by Charisse Vu 1H
Sun Jan 26, 2020 11:46 pm
Forum: Phase Changes & Related Calculations
Topic: Hess's Law
Replies: 5
Views: 32

Re: Hess's Law

Hess's Law states that enthalpy change at each step of a reaction can be added together to give a total enthalpy change because enthalpy is a state function and is therefore additive.
by Charisse Vu 1H
Sun Jan 26, 2020 11:44 pm
Forum: Phase Changes & Related Calculations
Topic: State Property
Replies: 6
Views: 41

Re: State Property

State properties are the same as state functions. The path that is taken to get from one point to another is not important. An example Professor Lavelle gave in class was altitude. Enthalpy is another example.
by Charisse Vu 1H
Mon Jan 13, 2020 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The Value of Kw
Replies: 3
Views: 21

The Value of Kw

Can the value of Kw ever change? I remember Professor Lavelle talking about temperature being able to change Kw but I don't really recall why or if temperature was the only factor that could change its value.
by Charisse Vu 1H
Mon Jan 13, 2020 5:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Are Lectures Bruincasted?
Replies: 10
Views: 136

Re: Are Lectures Bruincasted?

I don't believe that lectures are bruincasted! They aren't found anywhere on his website.
by Charisse Vu 1H
Mon Jan 13, 2020 4:12 pm
Forum: Ideal Gases
Topic: Kc and Kp
Replies: 5
Views: 34

Re: Kc and Kp

Kc and Kp both measure the equilibrium constant of a reaction. Kc is used when calculating in terms of concentration whereas Kp is used when calculating in terms of pressure. Typically, you would calculate the Kp of a reaction that is made up of all gases, but both Kp and Kc should be the same since...
by Charisse Vu 1H
Mon Jan 13, 2020 4:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.3
Replies: 5
Views: 33

Re: 5J.3

When you remove NO, the reaction favors the products because it wants to reach equilibrium. Since there is now less NO, and therefore products, the reaction proceeds forward to produce more products. This causes NH3 (reactant) to decrease.
by Charisse Vu 1H
Mon Jan 13, 2020 4:02 pm
Forum: Student Social/Study Group
Topic: F19 Final
Replies: 4
Views: 62

Re: F19 Final

They will be available third week at 3034 Young Hall as per Professor Lavelle's email.
by Charisse Vu 1H
Mon Jan 06, 2020 10:40 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure's Effect on Equilibrium
Replies: 6
Views: 91

Pressure's Effect on Equilibrium

Why is it that when pressure is increased by adding an inert gas to a reaction, the K value does not change? Also, what happens when pressure is decreased?
by Charisse Vu 1H
Mon Jan 06, 2020 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.23
Replies: 1
Views: 39

Re: 5I.23

Hi! When you make your ICE table, the x value that you use to add and subtract to and from the reactants/products is actually equal to .478 M, which was given in the original problem because it is given that the equilibrium concentration (the E section of the ICE table) is 0.478 M.
by Charisse Vu 1H
Mon Jan 06, 2020 10:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant for Solids/Gases
Replies: 5
Views: 54

Re: Equilibrium Constant for Solids/Gases

You do take solids and liquids out of the equilibrium constant equation, but not including them does not eliminate the numerator. A quick google search indicated that the activity (I believe Professor Lavelle briefly mentioned that we would be considering concentrations to be the same as the activit...
by Charisse Vu 1H
Mon Jan 06, 2020 10:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module: Equilibrium Part 3 Question 17
Replies: 3
Views: 48

Re: Module: Equilibrium Part 3 Question 17

Remember that when solving a quadratic equation, x will have two values. The other value that you have not yet solved for will probably give you the right answer to the question! (Your quadratic equation is correct, you just need to solve for the other x).
by Charisse Vu 1H
Mon Jan 06, 2020 10:20 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Equilibrium and Gases
Replies: 3
Views: 49

Re: Equilibrium and Gases

When pressure is increased by decreasing the volume, equilibrium shifts to to the side with less moles of gas because the concentrations of each compound is being increased according to the equation P=n/v. If pressure is increased by decreasing the volume, then the concentration increases since v is...
by Charisse Vu 1H
Wed Dec 04, 2019 12:27 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Drawing structures on the final
Replies: 3
Views: 46

Re: Drawing structures on the final

I don't believe you need to know how to draw these compounds. I think you just need to know how to name/identify them.
by Charisse Vu 1H
Wed Dec 04, 2019 12:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Videos on polydentate ligands?
Replies: 2
Views: 28

Re: Videos on polydentate ligands?

I think that this video is pretty helpful! https://www.youtube.com/watch?v=r4H5XjJPn58. Hope this helps :)
by Charisse Vu 1H
Wed Dec 04, 2019 12:20 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Review Session
Replies: 6
Views: 110

Re: Final Review Session

Yes! Lyndon, one of the UAs, posted another review packet under the name "Marshmallow". There is also a chemistry review session this Friday!
by Charisse Vu 1H
Wed Dec 04, 2019 12:18 pm
Forum: Identifying Acidic & Basic Salts
Topic: pH of salt solutions
Replies: 2
Views: 26

pH of salt solutions

Why do certain ions in salts not affect the pH of the solution?
by Charisse Vu 1H
Wed Dec 04, 2019 12:11 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 6.4
Replies: 1
Views: 34

Re: 6.4

The pH of pure water is 7. The equation to find pH is pH=-log[H3O+]. Substituting 7 into the equation, you would find that the concentration of hydronium ions is 1*10^-7. Then, to find the number of ions present, you would then do the following: \frac{1*10^-7mol}{L} (\frac{0.100L}{1})(\f...
by Charisse Vu 1H
Wed Dec 04, 2019 12:05 pm
Forum: Hybridization
Topic: Hybridization of terminal atoms
Replies: 2
Views: 40

Re: Hybridization of terminal atoms

No, I don't believe you need to know the hybridization of terminal atoms. I believe you just need to know the hybridization of central atoms.
by Charisse Vu 1H
Tue Nov 26, 2019 9:44 am
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Content
Replies: 14
Views: 138

Re: Final Exam Content

I believe that the final exam will cover everything we learned this quarter. Just as how the midterm also covered the high school material that we covered in the first two weeks, the final will probably be similarly formatted and pull questions from the different topics we learned this quarter.
by Charisse Vu 1H
Tue Nov 26, 2019 9:38 am
Forum: Bronsted Acids & Bases
Topic: Lewis Structures of Acid/Base reactions
Replies: 3
Views: 40

Re: Lewis Structures of Acid/Base reactions

I don't believe you would have to know how to draw out the lewis structures for acid/base reactions! However, I feel that knowing the lewis structures of acid/base reactions will strengthen and further your understanding of how these reactions work.
by Charisse Vu 1H
Tue Nov 26, 2019 9:34 am
Forum: Bronsted Acids & Bases
Topic: Equlibrium Constant Expression for Strong Acids/Bases
Replies: 3
Views: 25

Re: Equlibrium Constant Expression for Strong Acids/Bases

Ka and Kb don't exist for strong acids and bases because they dissociate completely in solution. If you recall the formula for calculating the equilibrium constants, K_{a}=\frac{[H^{+}][A^{-}]}{[HA]} you will see that the concentration of the acid itself is in the denominator. Since strong acids/bas...
by Charisse Vu 1H
Tue Nov 26, 2019 9:24 am
Forum: Sigma & Pi Bonds
Topic: Strength of the Bonds
Replies: 2
Views: 37

Re: Strength of the Bonds

Sigma bonds are actually stronger than pi bonds. Sigma bonds have more of a linear overlap whereas pi bonds have a "parallel" overlap. The electrons are held more tightly to the nuclei of sigma bonds than pi bonds. https://chem.libretexts.org/@api/deki/files/78352/CK12_Screenshot_9-20-3.pn...
by Charisse Vu 1H
Tue Nov 26, 2019 9:20 am
Forum: Dipole Moments
Topic: Intermolecular force
Replies: 5
Views: 358

Re: Intermolecular force

Yes! It would be perfectly fine to refer to intermolecular forces as stronger or weaker. It is true that the stronger the intermolecular force is, the harder it is to break the bonds between the molecules.
by Charisse Vu 1H
Sun Nov 24, 2019 11:57 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: bonds
Replies: 2
Views: 80

Re: bonds

It can be nonpolar if the dipole moments cancel each other out. For example, carbon dioxide has polar bonds but the overall molecule is nonpolar. The dipole moments face each other and the molecule is also symmetrical, cancelling each other out and making the molecule nonpolar.
by Charisse Vu 1H
Sun Nov 24, 2019 11:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: electron and molecular geometry of H20
Replies: 3
Views: 38

Re: electron and molecular geometry of H20

The electron geometry of H2O is tetrahedral because of the two sets of lone pairs. Therefore, its molecular geometry is bent (AX2E2).
by Charisse Vu 1H
Sun Nov 24, 2019 11:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shape of carbon Dioxide
Replies: 10
Views: 65

Re: Molecular shape of carbon Dioxide

The molecular shape of carbon dioxide is bent because it has no lone pairs.
by Charisse Vu 1H
Sun Nov 24, 2019 11:47 pm
Forum: Bond Lengths & Energies
Topic: Polarity
Replies: 5
Views: 119

Re: Polarity

Polar molecules tend to have higher boiling/melting points because they have greater intermoleculr forces than nonpolar molecules do. Nonpolar molecules only have van der Waals forces acting between molecules., which is the weakest form of intermolecular force. Polar molecules have dipoles that give...
by Charisse Vu 1H
Sun Nov 24, 2019 11:44 pm
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 21
Views: 114

Re: Sigma and Pi Bonds

In a molecule, you can identify sigma and pi bonds by counting the number of single, double, and triole bonds it has. Every single bond is a sigma bond, every double bond has 1 sigma bond and 1 pi bond, and every triple bond has 1 sigma bond and 2 pi bonds.
by Charisse Vu 1H
Sat Nov 16, 2019 10:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: dipole-dipole
Replies: 3
Views: 45

Re: dipole-dipole

The OH group on the molecule is what makes the molecule polar. Its shape is a tetrahedral and the OH group is much more negative than the rest of the molecule.
by Charisse Vu 1H
Sat Nov 16, 2019 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moments
Replies: 2
Views: 24

Re: Dipole moments

You would add an arrow. Make sure the bonds in the lewis structure are just lines!
by Charisse Vu 1H
Sat Nov 16, 2019 10:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 45

Re: Bond Angles

Sometimes, the angles can differ slightly because of how electronegative the atoms are in a molecule. If an atom is more electronegative, then the bond angle may be reduced.
by Charisse Vu 1H
Sat Nov 16, 2019 10:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Subscript on E
Replies: 5
Views: 52

Re: Subscript on E

Hi!

You can write it however you want :) they are the same thing, but putting a subscript of 1 may make it clearer for the person grading the exams.
by Charisse Vu 1H
Sat Nov 16, 2019 10:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent and Angular?
Replies: 6
Views: 61

Re: Bent and Angular?

Bent and angular are synonymous but typically, bent is used more often!
by Charisse Vu 1H
Fri Nov 08, 2019 12:41 pm
Forum: Photoelectric Effect
Topic: frequency and ejection of electrons
Replies: 7
Views: 195

Re: frequency and ejection of electrons

The photoelectric effect states that there is a certain amount of energy (threshold energy) needed for an electron to be ejected. The frequency of the incoming photon is what determines whether an electron can be ejected. If the photon has a high enough frequency so that its energy surpasses that of...
by Charisse Vu 1H
Fri Nov 08, 2019 12:33 pm
Forum: DeBroglie Equation
Topic: Light waves
Replies: 2
Views: 92

Re: Light waves

You can only use c=(wavelength)(frequency) and E=h(frequency) for light waves. De Broglie's equation is used only for things with mass, and light does not have mass. Therefore, De Broglie can not be used for light waves.
by Charisse Vu 1H
Fri Nov 08, 2019 12:27 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Interaction Potential Energy
Replies: 3
Views: 33

Re: Interaction Potential Energy

Alpha represents the polarizability of an atom and depends on the number of electrons and size of the atom. R in the equation represents the radius. So, according to the equation, the interaction potential energy is proportional to .
by Charisse Vu 1H
Fri Nov 08, 2019 12:23 pm
Forum: DeBroglie Equation
Topic: De Broglie Equation Derivation and Use
Replies: 7
Views: 184

Re: De Broglie Equation Derivation and Use

We don't necessarily need to know how to derive De Broglie's Equation. Just know that De Broglie's Equation is used when calculating the wavelength or frequency of anything with mass, such as electrons.
by Charisse Vu 1H
Sun Nov 03, 2019 5:18 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power
Replies: 3
Views: 35

Re: polarizing power

Large distortion refers to the distortion of the electron cloud when an ionic compound is formed. The cation in the ionic compound pulls the anion's electrons closer to itself, distorting the electron cloud in the direction of the cation. That is why small cations have such high polarizing power.
by Charisse Vu 1H
Sun Nov 03, 2019 5:13 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power vs. polarizability
Replies: 1
Views: 35

Re: polarizing power vs. polarizability

Polarizing power is the ability of an atom/ion to cause large distortions in the electron cloud of another, whereas polarizability refers to atoms or ions that readily undergo large distortions, such as iodide. Iodide is highly polarizable because it has a low effective nuclear charge and its outerm...
by Charisse Vu 1H
Sun Nov 03, 2019 5:11 pm
Forum: Lewis Structures
Topic: structure stability
Replies: 2
Views: 20

Re: structure stability

Bond order is simply the number of bonds that link a specific pair of atoms (from the textbook). For example, the bond order in the molecule is three, since they are bound by a triple bond. To determine the most stable structure, you should try to get the formal charges on each atom of the molecule ...
by Charisse Vu 1H
Sun Nov 03, 2019 5:03 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Pattern?
Replies: 1
Views: 40

Re: Electron Configuration Pattern?

Hi! There's actually a really handy diagram that helps you determine electron configuration of an atom much easier. https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwi5gaHKrM_lAhUToZ4KHZjxBGwQjRx6BAgBEAQ&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F326511041712732752%2F&...
by Charisse Vu 1H
Fri Nov 01, 2019 2:05 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 4
Views: 59

Re: Resonance

I don't believe that resonance structures are more reactive. In fact, I believe thay resonance actually stabilizes molecules because it delocalizes the molecule and lowers the overall energy. The electrons have a greater space to occupy.
by Charisse Vu 1H
Sun Oct 27, 2019 3:25 pm
Forum: Ionic & Covalent Bonds
Topic: ionization
Replies: 5
Views: 44

Re: ionization

Ionization energy is the energy needed to remove an electron from an atom. It has a trend in the periodic table because as you move across a period from left to right, the ionization energy increases, and as you move up a group the ionization energy also increases. It increases from left to right be...
by Charisse Vu 1H
Sun Oct 27, 2019 3:18 pm
Forum: Trends in The Periodic Table
Topic: Ionization and Electron Affinity
Replies: 5
Views: 72

Re: Ionization and Electron Affinity

Ionization energy refers to the energy needed to remove an electron from an atom (in its gas phase) while electron affinity refers to the energy released when an electron is added to an atom (in its gas phase). Electron affinity could also be explained as how much an atom attracts/gains electrons!
by Charisse Vu 1H
Sun Oct 27, 2019 3:13 pm
Forum: Trends in The Periodic Table
Topic: Central Atom
Replies: 13
Views: 94

Re: Central Atom

The atom with the lowest ionization energy is commonly used as the central atom when drawing lewis structures! Dr. Lavelle talked about this briefly in lecture :)
by Charisse Vu 1H
Sun Oct 27, 2019 3:11 pm
Forum: Quantum Numbers and The H-Atom
Topic: 1D.23
Replies: 1
Views: 38

Re: 1D.23

For b, there is actually only 1 orbital because n=4 refers to the 4th shell, l=2 refers to the d subshell, and m(l)=-2 specifies a single orbital. Therefore, part b only has 1 orbital. For part c, there are 4 orbitals because n=2 refers to the 2nd shell. In the second shell, the s and p subshells ex...
by Charisse Vu 1H
Sun Oct 27, 2019 2:55 pm
Forum: Resonance Structures
Topic: Bond lenghts.
Replies: 11
Views: 91

Re: Bond lenghts.

I don't believe that we have to know how to find specific bond lengths. We just have to understand the differences in lengths of double and single bonds. Bond lengths within molecules with resonance must also be considered. The bond lengths in molecules with resonance are more like an "average&...
by Charisse Vu 1H
Sun Oct 20, 2019 5:35 pm
Forum: Quantum Numbers and The H-Atom
Topic: 1D.23
Replies: 1
Views: 31

Re: 1D.23

Yes, your answer would be a summation of all the possible values for m and l given that n=2. If n=2, l must be 0 or 1 and m could therefore be -1, 0, or 1 if l=1. If l=0, then m could only be 0. The total number of orbitals then would be 4.
by Charisse Vu 1H
Sun Oct 20, 2019 5:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Spin
Replies: 2
Views: 44

Re: Electron Spin

When two electrons are paired, it means that they exist in the same orbital within a subshell. When electrons are parallel, they are filling the orbitals singly before pairing. According to Hund's Rule, this happens because when there are two or more orbitals with equal energies, electrons will fill...
by Charisse Vu 1H
Sun Oct 20, 2019 5:19 pm
Forum: DeBroglie Equation
Topic: 1B.21
Replies: 3
Views: 79

Re: 1B.21

This question is dealing with deBroglie's equation, as it is asking for the wavelength of something that has mass and velocity (momentum). Since the units are not what we want, we must use dimensional analysis to convert ounces to kilograms and miles per hour to meters per second. It is given that o...
by Charisse Vu 1H
Sun Oct 20, 2019 5:09 pm
Forum: DeBroglie Equation
Topic: DeBroglie Equation
Replies: 11
Views: 125

Re: DeBroglie Equation

You would use the DeBroglie equation when trying to determine the wavelength of anything with momentum (mass * velocity). It is used in particular for items with very small masses, such as electrons. Typically, when the question is asking about the wavelength or velocity of an electron or a small pa...
by Charisse Vu 1H
Sun Oct 20, 2019 5:04 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 8
Views: 97

Re: Orbitals

The reason why Scandium is written as [Ar] 3d1 4s2 is because after the 20th element in the periodic table (Calcium), the 3d orbitals have a slightly lower energy than the 4s orbitals. Therefore, you would start filling the 3d orbitals until it is full. The 4s orbital is filled first because it is i...
by Charisse Vu 1H
Fri Oct 11, 2019 12:51 pm
Forum: Empirical & Molecular Formulas
Topic: Molecular formula
Replies: 6
Views: 390

Re: Molecular formula

You would first need to find the empirical formula using the mass percentages. You would assume that there is 100g of the molecule and convert the grams of each atom into moles. Then, you would divide the moles by the smallest number of moles to find the ratio of atoms in the molecule. To find the m...
by Charisse Vu 1H
Fri Oct 11, 2019 12:47 pm
Forum: SI Units, Unit Conversions
Topic: How to express answers
Replies: 13
Views: 262

Re: How to express answers

I don't believe that sig figs are too important in this class. My TA told us that sig figs are not too big of a deal, as long as you do not round to whole numbers or to only 1 decimal place when the answer should clearly have 2 or 3 decimal places. As for scientific notation, I believe that it is mo...
by Charisse Vu 1H
Fri Oct 11, 2019 12:38 pm
Forum: Administrative Questions and Class Announcements
Topic: Posts
Replies: 6
Views: 77

Re: Posts

The 5 homework questions are always due in your discussion! As for the 5 posts for chemistry community, you need to have all your posts published by 11:59 PM Sunday night. I recommend that you contribute to discussions asking more conceptual questions, rather than homework problems. I feel that it i...
by Charisse Vu 1H
Fri Oct 11, 2019 12:20 pm
Forum: Empirical & Molecular Formulas
Topic: Decimals to Whole Numbers
Replies: 6
Views: 257

Re: Decimals to Whole Numbers

I believe that rounding from 3.1 to 3 would be okay if you are solving for empirical formulas. If the number is about .1 away from a whole number, I don't believe that it would hurt to round it to a whole number. However, rounding to whole numbers in other problems besides solving for empirical/mole...
by Charisse Vu 1H
Fri Oct 11, 2019 12:08 pm
Forum: General Science Questions
Topic: Balancing Chemical Equations
Replies: 5
Views: 97

Re: Balancing Chemical Equations

This reaction is a combustion reaction, so O2 would be one of the reactants. Therefore, the chemical equation would be O2 + C7H16 -> CO2 + H2O. You would first balance the carbon, so you would put 7 as the stoichiometric coefficient in front of the carbon dioxide on the products side. Then, you woul...
by Charisse Vu 1H
Thu Oct 03, 2019 10:45 pm
Forum: SI Units, Unit Conversions
Topic: Advice
Replies: 3
Views: 80

Re: Advice

You just need to use dimensional analysis! Dimensional analysis utilizes the cancellation of units.
by Charisse Vu 1H
Thu Oct 03, 2019 10:37 pm
Forum: SI Units, Unit Conversions
Topic: Mass % comp accuracy F5
Replies: 5
Views: 127

Re: Mass % comp accuracy F5

Yes, I believe it's totally fine! It depends on the periodic table you are using too. Some periodic tables round off at different sig figs so you should be fine.
by Charisse Vu 1H
Wed Oct 02, 2019 1:29 am
Forum: Empirical & Molecular Formulas
Topic: Homework problem E3 [ENDORSED]
Replies: 1
Views: 64

Re: Homework problem E3 [ENDORSED]

I believe this question is simpler than what it seems. In the question, the gallium atoms are literally represented by the blue circles on the scale. If you count them, you would see that there are 9 "atoms" of gallium on the left hand side of the scale. Comparing the molar masses of galli...
by Charisse Vu 1H
Wed Oct 02, 2019 1:24 am
Forum: Molarity, Solutions, Dilutions
Topic: G 25
Replies: 7
Views: 97

Re: G 25

Since you are doubling the volume of the solution 90 times, the final volume would be much greater than the initial volume. The question asks how many molecules would be present in only 10. mL of the final solution. Since the volume has increased so dramatically, 10. mL of the final solution would c...

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