## Search found 102 matches

Sat Mar 14, 2020 9:27 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: h20 in our rate law
Replies: 3
Views: 93

### Re: h20 in our rate law

I don't believe that I have ever seen H2O in a rate law, so I would assume that it would not be included in a rate law nor would there be a question like that!
Sat Mar 14, 2020 9:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A- frequency factor
Replies: 3
Views: 91

### Re: A- frequency factor

I am confused about A. Will we be given A? Because I am not really sure how to find it nor have I really encountered a problem that needed it.
Sat Mar 14, 2020 9:22 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts on Final
Replies: 6
Views: 156

### Re: Catalysts on Final

I would imagine there wouldn't be an incredibly difficult question on catalysts, especially one requiring math, since we only went over catalysts very briefly in class.
Thu Mar 12, 2020 12:46 am
Forum: Second Order Reactions
Topic: 7B.3
Replies: 5
Views: 125

### Re: 7B.3

Why do we use the first order formula for this problem? Since there is 2A does that mean it is second order, or is that only when there are 2 different reactants?
Thu Mar 12, 2020 12:24 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7A.17
Replies: 2
Views: 92

### 7A.17

I am confused on this question, because when I don't convert from mmol to mol, I get the answer k=2.85 L 4 /mmol -4 *s -1 . While this is the same numbers as the answer key, the answer converts all the values to moles first and gets the answer to be 2.85x10 12 L 4 /mol -4 *s -1 . Even when I convert...
Sun Mar 08, 2020 11:54 pm
Forum: General Rate Laws
Topic: Making one reactant concentration small
Replies: 3
Views: 70

### Making one reactant concentration small

In reactions with more than one reactant, why are we allowed to make one reactant small and the other ones large in order to find the rate law?
Sun Mar 08, 2020 11:48 pm
Forum: General Rate Laws
Topic: Overall rate law
Replies: 8
Views: 169

### Overall rate law

I am confused as to why the overall rate law is the rate law of just the slowest step. I understand why the slow step must determine the rest of it, but why are the species in the other steps not included in the overall rate law?
Sun Mar 08, 2020 11:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Ways to Approach Reaction Mechanisms
Replies: 3
Views: 47

### Ways to Approach Reaction Mechanisms

At the end of Friday 3/6 lecture, Dr. Lavelle discussed ways to approach proposed reaction mechanisms. However, I remember him saying that we would never use these methods (or something along those lines). So should we know these approaches?
Wed Mar 04, 2020 6:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61
Replies: 3
Views: 175

### 5.61

For the photosynthesis reaction, water is a reactant. So when it asked how the reaction would shift when more water was added, I assumed it would shift towards the products. However, the answer key says that because water is a liquid, it is by definition present at unit concentration, so changing th...
Wed Mar 04, 2020 1:58 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.17
Replies: 1
Views: 23

### 5G.17

Question: Depict the progress of the reaction graphically for the reaction in Exercise 5G.13. I understand why I is a reactant and I 2 is a product, but I do not understand why the lines do not intersect at all. In the example figures shown, the product always begins at 0 while later the reactant go...
Sun Mar 01, 2020 11:34 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Value of K
Replies: 2
Views: 68

### Re: Value of K

I believe it depends on the situation? You would still use the Nernst equation to figure out what the value of K is.
Sun Mar 01, 2020 11:32 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Amount of products and reactants
Replies: 2
Views: 67

### Re: Amount of products and reactants

I just know that when using the Nernst equation, having more products than reactants means that the Q value will be larger and a nice positive E standard potential value tells us that the reaction favors products when it reaches equilibrium.
Sun Mar 01, 2020 11:27 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Making a battery
Replies: 1
Views: 47

### Making a battery

In my notes I have written that we could make a battery by making an electron solution and diluting it, but that it'll have low voltage. I'm just wondering why this is true?
Sun Mar 01, 2020 11:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E of concentration cell
Replies: 1
Views: 26

### E of concentration cell

Why is the E value of a concentration cell always 0 V?
Sun Mar 01, 2020 11:22 pm
Forum: General Rate Laws
Topic: Preferred way to write reaction rate
Replies: 5
Views: 95

### Preferred way to write reaction rate

Can someone please explain why putting the fraction in front of a reaction rate is preferred? For example, with the example that Dr. Lavelle did in class, wouldn't it be easier to just place a 2 in front of one of the substances instead of a 1/2 in front of 2 different substances? Thank you!
Sun Feb 23, 2020 11:45 pm
Forum: Balancing Redox Reactions
Topic: half reaction
Replies: 10
Views: 153

### Re: half reaction

I am confused about the same thing. In my discussion, my TA included water in the acidic redox reaction (with H2O and H3O+) but not the basic one (she only included OH- with no H2O). I am confused as to why.
Sun Feb 23, 2020 11:43 pm
Forum: Balancing Redox Reactions
Topic: Tips for Balancing Reactions
Replies: 3
Views: 64

### Re: Tips for Balancing Reactions

My TA gave us these tips! In an acidic solution: If there is more O in the reactants, use H30+--->H2O If there is more O in the products, use H2O--->H3O+ In a basic solution: If there is more O in the reactants, use H2O--->OH- If there is more O in the products, use OH- ---> H2O Hope this helps!
Sun Feb 23, 2020 11:40 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Estimating Delta G
Replies: 2
Views: 58

### Estimating Delta G

I heard Dr. Lavelle say multiple times that the closest you can get to estimating the delta G is by calculating the voltage difference, but I am kind of confused as to what this means and as to why this is true? If someone could explain it I would really appreciate it, thank you!
Sun Feb 23, 2020 11:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Max Cell Potential and Free Energy Difference
Replies: 2
Views: 100

### Re: Max Cell Potential and Free Energy Difference

The maximum work of the cell Wmax is equal to the delta G Gibbs free energy in a redox reaction in a battery at constant temperature and pressure.
Sun Feb 23, 2020 11:36 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Convention for cell diagrams
Replies: 3
Views: 59

### Convention for cell diagrams

In the shorthand notation for cell diagrams (with the single and double lines), Dr. Lavelle said that he wrote it differently in his notes and that the convention is usually that the two electrodes are at both ends. I was wondering what this means exactly? And which way should we write it?
Sun Feb 16, 2020 11:27 pm
Forum: Van't Hoff Equation
Topic: Constant delta H
Replies: 4
Views: 81

### Constant delta H

I am confused why delta H remains constant in the Van't Hoff equation. Can someone explain this to me please?
Sun Feb 16, 2020 11:24 pm
Forum: Balancing Redox Reactions
Topic: oxidation number
Replies: 10
Views: 140

### Re: oxidation number

You look at the known charges or the charges that are present on the specific element in the reaction, and make it equal that charge. If there is no charge present on a compound then the oxidation numbers cancel out!
Sun Feb 16, 2020 11:23 pm
Forum: Balancing Redox Reactions
Topic: Rules for oxidation numbers
Replies: 6
Views: 53

### Re: Rules for oxidation numbers

Ions always have a charge! The definition of ions is that they have a charge.
Wed Feb 12, 2020 12:43 am
Forum: Calculating Work of Expansion
Topic: Positive or negative work
Replies: 15
Views: 326

### Positive or negative work

Is work positive when work is done on the system? I am finding varying answers online which is making me confused.
Tue Feb 11, 2020 11:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Formula Sheet
Replies: 7
Views: 138

### Formula Sheet

Does anyone know what formula sheet will be given on the midterm? Is it the same one as the one given for Test 1, or is it the one online on his website? Because the one on his website has many more equations than the one given for Test 1...
Sun Feb 09, 2020 6:46 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Delta S Universe
Replies: 3
Views: 67

### Delta S Universe

Can the equation $\bigtriangleup S_{univ}=\bigtriangleup S_{sys}+\bigtriangleup S_{surr}$ only apply to reversible reactions? Or can it apply to irreversible reactions as well?
Sun Feb 09, 2020 6:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Favorability of Endothermic Reactions
Replies: 5
Views: 79

### Favorability of Endothermic Reactions

Would we expect an endothermic reaction to be more favorable at a very high temperature?
Sun Feb 09, 2020 6:39 pm
Forum: Calculating Work of Expansion
Topic: Isobaric and Isochoric
Replies: 5
Views: 116

### Isobaric and Isochoric

Are we expected to know the definitions of isobaric and isochoric? I don't recall ever going over these terms in class.
Sun Feb 09, 2020 6:37 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: System releasing energy
Replies: 2
Views: 24

### System releasing energy

To clarify, if a system releases energy this energy is now free and available to do work. Does this result in a negative change in Gibbs free energy?
Thu Feb 06, 2020 12:08 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.9
Replies: 1
Views: 19

### 4A.9

The answer key says that the heat lost by the metal= -heat gained by water. I was just wondering why the negative sign wasn't the other way around? Shouldn't the heat lost by the metal be negative since lost heat is negative?
Sun Feb 02, 2020 11:13 pm
Forum: Calculating Work of Expansion
Topic: reversible expansion
Replies: 6
Views: 53

### Re: reversible expansion

This small change in parameter or pressure can be done using a piston.
Sun Feb 02, 2020 11:10 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: when is w=0 and when is q=0?
Replies: 6
Views: 487

### Re: when is w=0 and when is q=0?

Sun Feb 02, 2020 11:07 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Resources
Replies: 3
Views: 54

### Re: Resources

Although these are not online resources, the sessions that Dr. Lavelle have set up are very helpful and extensive!
Sun Feb 02, 2020 11:05 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: internal energy and work
Replies: 4
Views: 50

### Re: internal energy and work

I believe that the change in internal energy is always equal to the sum of heat gained or lost by the system and the work done on or by the system.
Sun Feb 02, 2020 10:54 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: expansion work
Replies: 4
Views: 72

### Re: expansion work

I believe that a force opposing the expansion of a piston would be the air that is in the surroundings, although I don't believe that the force would be too much unless there was some other outlying force.
Sun Jan 26, 2020 6:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of formation of O2
Replies: 4
Views: 39

### Standard enthalpy of formation of O2

Why is the standard enthalpy of formation of O2 0? I don't believe I caught the reason why in class.
Sun Jan 26, 2020 6:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Method 2
Replies: 2
Views: 28

### Using Method 2

Since method 2 is the most inaccurate method, when should we ever use it? It seems as though this is the most complicated a time consuming method with the bond enthalpies, so would there ever be a case where we should use this method as opposed to methods 1 or 3?
Sun Jan 26, 2020 6:26 pm
Forum: Phase Changes & Related Calculations
Topic: Why does steam cause burns?
Replies: 29
Views: 316

### Re: Why does steam cause burns?

When steam comes into contact with skin, it encounters a phase change to a liquid and immediately releases many more kJ of energy as opposed to just boiling water which does not have to go through a phase change and therefore releases less kJ of energy.
Sun Jan 26, 2020 6:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta H and delta U
Replies: 2
Views: 20

### Re: delta H and delta U

Did we ever learn about delta U in class? I do not believe I am familiar with it.
Sun Jan 26, 2020 6:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy Use
Replies: 1
Views: 17

### Standard Reaction Enthalpy Use

It seems as though standard reaction enthalpies are never how they actually are in real life in the lab. How would this be accurate then when using the standard reaction enthalpies to compare reactions?
Sun Jan 19, 2020 11:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Autoprotolysis
Replies: 5
Views: 110

### Re: Autoprotolysis

Dr. Lavelle gave an example of autoprotolysis in class, which is 2H2O ---> H3O+ + OH-. This is one of the most common equilibrium reactions that shows the equilibrium constant and therefore the autoprotolysis constant Kw.
Sun Jan 19, 2020 11:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ice Tables
Replies: 4
Views: 51

### Re: Ice Tables

Yes, we use ICE tables when we want to find the concentration of a product in an equilibirum reaction involving either a weak acid or base.
Sun Jan 19, 2020 11:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 6
Views: 145

### Re: Q

Q is the ratio between products and reactants that is found when the reaction has not yet reached equilibrium. K is the ratio when the reaction is already at equilibrium. Therefore, we can use Q to see which way the reaction will proceed.
Sun Jan 19, 2020 11:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approximations
Replies: 3
Views: 39

### Re: Approximations

I believe that this means that x was not small enough to approximate in the first place, which means that the K was not small enough either.
Sun Jan 19, 2020 11:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different ways to write K
Replies: 3
Views: 40

### Different ways to write K

I know that there are multiple different versions of K, such as Kc, Keq, etc. I was wondering if it mattered what we wrote as the subscript or if it is fine if we simply just write K (with no subscript)? Thank you!
Fri Jan 10, 2020 12:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Why Q would be greater than K
Replies: 5
Views: 39

### Why Q would be greater than K

When a reaction is at equilibrium, I think that it stays at equilibrium. I presume that Q would not become greater than K if the reaction at equilibrium was left to run for a very long period of time. Is this correct?
Fri Jan 10, 2020 12:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating eq with percentages of reaction
Replies: 3
Views: 20

### Re: Calculating eq with percentages of reaction

You can use the percentages in order to find the concentrations of the reactants and products. When you know the percentages you can calculate the moles and therefore the molarity if you are given enough information.
Thu Jan 09, 2020 2:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Initial Concentrations of Reactants and Products
Replies: 2
Views: 25

### Re: Initial Concentrations of Reactants and Products

The reaction continues until it reaches equilibrium, at which that point the equilibrium constant ratio is reached. But remember that equilibrium is dynamic so the reaction never really stops going!
Thu Jan 09, 2020 2:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Using the "ICE" box
Replies: 8
Views: 107

### Re: Using the "ICE" box

You would only include gases and aqueous substances in these calculations!
Thu Jan 09, 2020 1:59 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Chemical Activity of a Compound
Replies: 5
Views: 45

### Re: Chemical Activity of a Compound

Dr. Lavelle said that chemical activity is a very advanced concept and that we don't need to worry about it! I think all we have to know is that it is the reason why there are no units for K, since chemical activity has no units.
Sat Dec 07, 2019 7:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Is carbonato a chelating ligand
Replies: 1
Views: 40

### Is carbonato a chelating ligand

Would carbonato (CO32-) be considered a chelating ligand? Is it monodentate or bidentate?
Sat Dec 07, 2019 6:51 pm
Forum: Lewis Acids & Bases
Topic: 6.21
Replies: 2
Views: 37

### Re: 6.21

I am also confused about this. I know the formal charge of Oxygen is 0 so we wouldn't want to change it, but wouldn't the nitrogen accepting a proton also change its formal charge to make it not 0?
Sat Dec 07, 2019 5:55 pm
Forum: Calculating the pH of Salt Solutions
Topic: HW 6D.11
Replies: 1
Views: 122

### HW 6D.11

I understand that for part e, Al3+ is a small highly charged transition metal therefore it attracts water molecules. However, how do we know that it binds to 6 H2O molecules?
Sat Dec 07, 2019 4:25 am
Forum: Lewis Acids & Bases
Topic: HW Problem J.9
Replies: 1
Views: 50

### HW Problem J.9

I find that I have a difficult time knowing what salt is produced in a neutralization reaction, especially between a weak acid and base such as in part b. How would we just know that NH3 and H3PO4 would form the salt (NH4)3PO4?
Tue Dec 03, 2019 12:15 am
Forum: Lewis Acids & Bases
Topic: Memorizing Charges of Transition Metals
Replies: 9
Views: 222

### Memorizing Charges of Transition Metals

I was just wondering if we have to know the charges of the transition metals? For example, if they say Zinc Nitrite for a neutralization reaction are we just supposed to know that zinc has a +2 charge?
Sun Dec 01, 2019 11:53 pm
Forum: Bronsted Acids & Bases
Topic: Acid/Base strength
Replies: 2
Views: 60

### Re: Acid/Base strength

For this particular example, I believe we take the bonds into account. Since tricholoracetic acid has Cl present instead of H as in acetic acid, the bonds are longer and therefore weaker since Cl is much larger than H. Since the bond is longer and weaker, it makes it easier to remove H+ ions, theref...
Sun Dec 01, 2019 11:48 pm
Forum: Bronsted Acids & Bases
Topic: bronsted vs lewis
Replies: 2
Views: 35

### Re: bronsted vs lewis

Bronsted and Lewis are simply definitions of how to describe an acid or a base. A Bronsted acid is a proton donor while a Lewis acid accepts an electron pair. It just depends on how you look at it. In high school, I was taught that we generally use the Bronsted definition more so perhaps that one is...
Sun Dec 01, 2019 11:44 pm
Forum: Bronsted Acids & Bases
Topic: Equilibrium Arrows for Strong Acid/Base Equations
Replies: 1
Views: 32

### Equilibrium Arrows for Strong Acid/Base Equations

I know the strong acids/bases completely dissociate in water. Therefore, should we use a single way arrow when writing the chemical equation or should we still use the two-way equilibrium arrow like we do for weak acids/bases?
Sun Dec 01, 2019 11:41 pm
Forum: Amphoteric Compounds
Topic: Memorizing Amphoteric Oxides
Replies: 2
Views: 56

### Memorizing Amphoteric Oxides

I know Dr. Lavelle mentioned that there is a diagonal band of amphoteric oxides that is between the metal and nonmetal oxides. Will we have to memorize all of the amphoteric oxides?
Sun Dec 01, 2019 11:30 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Relative Acidity
Replies: 1
Views: 26

### Relative Acidity

I do not believe I fully understand what relative acidity is. Is there some way to calculate this or is it just a set or properties used to determine the strength of an acid?
Tue Nov 26, 2019 2:46 am
Forum: Naming
Topic: H2O vs OH2
Replies: 3
Views: 65

### H2O vs OH2

I have noticed that in the answer key, the answers for aqua are sometimes written as H2O and sometimes they are written as OH2 to emphasize that the oxygen is attached to the metal atom. Is there a way to know which one to use when writing the formula for a coordination compound? Thank you!
Sun Nov 24, 2019 11:52 pm
Forum: Biological Examples
Topic: TM switching between oxidation states
Replies: 1
Views: 48

### TM switching between oxidation states

I know Dr. Lavelle said that transition metals have many oxidation states that make it good for electron transfer, and that since the energy difference between the energy states it not that large they can switch between oxidation states. This part confused me slightly. How and why would the oxidatio...
Sun Nov 24, 2019 11:50 pm
Forum: Biological Examples
Topic: Porphyrin Ligand Drawing
Replies: 1
Views: 60

### Porphyrin Ligand Drawing

I think I missed this one part during lecture: When Dr. Lavelle drew the curly squiggly line surrounding the whole porphyrin ligand part, what was that supposed to represent? Thank you!
Sun Nov 24, 2019 11:47 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Inorganic vs Organic Acids
Replies: 3
Views: 76

### Inorganic vs Organic Acids

Can someone please explain why inorganic acids tend to be stronger while organic acids tend to be weaker?
Sun Nov 24, 2019 11:45 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: lecture notes
Replies: 2
Views: 37

### Re: lecture notes

Just like how the octahedral VSEPR geometry meant that there are 6 atoms around the central atom, the same goes for ligands. If there are 6 ligands around the central transition metal then it is an octahedral complex.The same goes for the tetrahedral complex.
Sun Nov 24, 2019 11:44 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating compounds
Replies: 1
Views: 33

### Re: chelating compounds

I think that it does not absolutely always have to be that the attachments are on the same side, but I think that it is better this way so that the bonds/forces will be stronger with more sites to attach to.
Sun Nov 17, 2019 7:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear molecule with lone pairs
Replies: 3
Views: 57

### Re: Linear molecule with lone pairs

I believe that the linear part of a greater shape can have lone pairs, for example the linear region of the trigonal bipyramidal shape (the axial bond angle that is 180 degrees). However, I do not think it would be possible for a purely linear shape to have lone pairs on the central atom, or at leas...
Sun Nov 17, 2019 7:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 5
Views: 101

### Re: VSEPR

The shape is always determined by the number of bonding pairs and lone pairs for the VSEPR model. And then once we determine the shape based on those things, we can also see the bond angles according to that shape.
Sun Nov 17, 2019 7:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Other VSEPR shapes?
Replies: 2
Views: 37

### Other VSEPR shapes?

Are we only responsible for knowing the VSEPR shapes that Dr. Lavelle went over in lecture? I know that there is also T-shaped as I have learned in high school, but I don't believe that Dr. Lavelle went over that one. Thanks!
Sun Nov 17, 2019 7:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles for all VSEPR shapes?
Replies: 2
Views: 54

### Bond angles for all VSEPR shapes?

Do we have to know the bond angles for each VSEPR shape? I know in lecture Dr. Lavelle only went over the bond angles up to the bent/angular shape, but do we have to know them for seesaw and square planar too? Thank you!
Sun Nov 17, 2019 7:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Influence on Molecular Shape
Replies: 4
Views: 47

### Re: Influence on Molecular Shape

The lone pairs have an effect on both the shape and the name, because according to the shapes determined by VSEPR, the names are based upon the shapes. For example, the square planar shape is determined because of the placement of both the bonding pairs and the lone pairs.
Sun Nov 10, 2019 11:48 pm
Forum: Sigma & Pi Bonds
Topic: hybridization
Replies: 3
Views: 114

### Re: hybridization

From what we briefly learned in my discussion section, hybridization is the combining of atomic orbitals into new hybrid orbitals to pair electrons and form chemical bonds. We did several examples where we would first draw the lewis structure of the compound, for example BeCl 2 . Then we would deter...
Sun Nov 10, 2019 11:42 pm
Forum: Dipole Moments
Topic: Dipole Moment vs Interactions
Replies: 2
Views: 39

### Re: Dipole Moment vs Interactions

Dipole interactions form between two molecules that each exhibit dipole moments (meaning that the molecules has uneven charge). So within the molecule itself it would be called a dipole moment, but with two or more molecules it would be a dipole interaction because the molecules with dipole moments ...
Sun Nov 10, 2019 11:38 pm
Forum: Bond Lengths & Energies
Topic: Size
Replies: 13
Views: 159

### Re: Size

Bond distance/length increases with atomic size. For example, PF3 and NF3 have the same number of valence electrons but PF3 has a longer bond length bc P is large in atomic size/radius than F.
Sun Nov 10, 2019 11:35 pm
Forum: Bond Lengths & Energies
Topic: Boiling Points
Replies: 2
Views: 53

### Re: Boiling Points

Compounds with higher boiling points generally means that the bonds present in the compound are stronger, since it will require a higher temperature for the substance to change state. It requires a higher temperature because the bonds are stronger and therefore harder to break apart. This could sign...
Wed Nov 06, 2019 1:59 am
Forum: Octet Exceptions
Topic: 2C.5a
Replies: 1
Views: 59

### 2C.5a

I am confused as to how to draw the lewis structure for the ClO radical. Why wouldn't there be a double bond between Cl and O and how do we know that the unpaired electron belongs to Cl instead of O?
Sun Nov 03, 2019 2:28 am
Forum: DeBroglie Equation
Replies: 7
Views: 123

According to the review session I went to, you would use c = λv only for light since it incorporates the speed of light. You would then use the DeBroglie equation for anything else, as these items will most likely be given with a mass in the problem. You can incorporate that with the E=hv equation b...
Sun Nov 03, 2019 2:25 am
Forum: Properties of Electrons
Topic: Knowing masses
Replies: 2
Views: 156

### Re: Knowing masses

When you look at the formula sheet that Dr. Lavelle posted on his website, you can see that the masses of all of these are given. :)
Sun Nov 03, 2019 2:22 am
Forum: Properties of Electrons
Topic: Resonance Structures
Replies: 2
Views: 134

### Re: Resonance Structures

Whenever you are drawing a lewis structure, no matter if it is resonance or not, it is optimum to try to draw it with the least formal charge possible. But for different variations of a resonance structure, the overall formal charge should remain the same.
Sun Nov 03, 2019 2:20 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in Position and Uncertainty in Momentum
Replies: 4
Views: 176

### Re: Uncertainty in Position and Uncertainty in Momentum

I have the same issue understanding this concept. I understand how it works mathematically using the Heisenberg indeterminacy equation, but I do not quite understand it conceptually. If there is more uncertainty regarding the position, shouldn't there be more uncertainty about the momentum as well?
Sun Nov 03, 2019 2:16 am
Forum: Properties of Light
Topic: Wavelength and Type of Light
Replies: 3
Views: 128

### Wavelength and Type of Light

For the midterm, do we have to memorize the cutoffs for what wavelength corresponds with what type of light? For example, how visible light is a wavelength of 400-700nm. Do we have to know this for all the different types of light?
Tue Oct 29, 2019 2:41 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Number of orbitals
Replies: 1
Views: 36

### Number of orbitals

Can someone explain why s has 1 orbital, p has 3 orbitals, d has 5 orbitals, and f has 7? Is there a conceptual understanding behind this or is it something that we must memorize? Thank you!
Sun Oct 27, 2019 11:30 pm
Forum: Lewis Structures
Topic: Expanded valence shells
Replies: 3
Views: 43

### Re: Expanded valence shells

I was also wondering the same thing. Is it just P, S, and Cl or is it all the elements in the periods below (including Ga, Ge, etc.) that follow this expanded valence shell rule?
Sun Oct 27, 2019 11:27 pm
Forum: Ionic & Covalent Bonds
Topic: Boron's valence electrons
Replies: 2
Views: 46

### Boron's valence electrons

Can someone explain why boron can be satisfied by 6 valence electrons in its outer shell instead of 8? My classmate and I are confused as to the explanation behind this concept.
Sun Oct 27, 2019 11:24 pm
Forum: Ionic & Covalent Bonds
Topic: d-block Exceptions
Replies: 2
Views: 45

### d-block Exceptions

Are the only exceptions for the d5 and d10 rule Chromium, Copper, Molybdenum, and Silver? Or does it go to the periods below that too in the same group? (I know that Tungsten does not follow this rule, however.)
Sun Oct 27, 2019 11:19 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State
Replies: 11
Views: 188

### Re: Ground State

When one says ground state electron configuration, one can just assume to find the configuration with the lowest energy, meaning just the normal electron configuration. The word "ground-state" isn't asking you to find anything special in particular--just find the electron configuration as ...
Sun Oct 27, 2019 11:17 pm
Forum: Ionic & Covalent Bonds
Topic: 4s before 3d
Replies: 4
Views: 74

### Re: 4s before 3d

When looking at the periodic table and its blocks, one can see that the s block comes before the d block. So when going left to right through the periodic table and writing the electron configuration, you hit the 4th period of the s block before you hit the 3rd period of the d block (since s is to t...
Sun Oct 20, 2019 11:46 pm
Forum: DeBroglie Equation
Topic: Deriving the DeBrogile Equation
Replies: 8
Views: 112

### Re: Deriving the DeBrogile Equation

While I think it's not totally necessary to memorize and know the derivation, it might prove to be helpful since the equations used to derive it are equations that we should know and memorize anyways! This way we can have a greater knowledge of how these concepts work together which could hopefully ...
Sun Oct 20, 2019 11:42 pm
Forum: DeBroglie Equation
Topic: When to combine equations
Replies: 10
Views: 224

### Re: When to combine equations

I have had trouble understanding this as well. I never seem to know when to use which equation and when to manipulate them. I think the only thing that could help is maybe doing many more examples and going to the peer learning sessions!
Sun Oct 20, 2019 11:39 pm
Forum: DeBroglie Equation
Topic: Photon Equation
Replies: 4
Views: 95

### Re: Photon Equation

To add onto this, my TA stated that upon his further research, this concept of a photon having momentum but no mass is something that is simply something in physics and chemistry that is not very well understood and is simply accepted. So I don't think we have to worry too much about this!
Sun Oct 20, 2019 11:36 pm
Forum: DeBroglie Equation
Topic: equation conversions
Replies: 2
Views: 57

### Re: equation conversions

I have not seen this before. The DeBroglie equation cannot be used for light, so I'm not sure if it can be applied or combined with the equation for the energy of a photon?
Mon Oct 14, 2019 1:41 pm
Forum: DeBroglie Equation
Topic: Derivation of de Broglie's Equation
Replies: 1
Views: 41

### Re: Derivation of de Broglie's Equation

I was wondering the same thing and was slightly confused as to why we were using the equation for the speed of light and looking at a photon when the equation is not even to be used for light. I understand that conceptually the equation can only be used for particles with rest mass (so not light), b...
Mon Oct 14, 2019 1:37 pm
Forum: DeBroglie Equation
Topic: Objects equation is used for
Replies: 2
Views: 47

### Re: Objects equation is used for

In my notes, I wrote that Dr. Lavelle stated that we should only use this equation for particles with rest mass (so cannot be applied to light), but that it could be applied to everything else but light. However, it was then said that the equation works for any particle with momentum and that it sho...
Mon Oct 14, 2019 1:34 pm
Forum: DeBroglie Equation
Topic: Quantum Mechanics Electron Diagram
Replies: 1
Views: 63

### Quantum Mechanics Electron Diagram

Could someone explain the diagram of the electrons with the "Allowed energy level" and "Not allowed" under the QM Description of Atoms slide from his lecture on 10/11? I know that these images were still ones from a how it is supposed to be moving in real life, but I still don't ...
Mon Oct 14, 2019 1:30 pm
Forum: DeBroglie Equation
Topic: De Broglie's Equation
Replies: 17
Views: 277

### Re: De Broglie's Equation

While all the previous replies have stated that light doesn't have mass and I agree, I just wanted to add that I remember Dr. Lavelle saying that the equation can only be used for particles with rest mass (mass at rest). It can be applied to everything else but light.
Mon Oct 14, 2019 1:26 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy in Position (delta x)
Replies: 1
Views: 28

### Indeterminacy in Position (delta x)

Hi, I am slightly confused about the example that Dr. Lavelle showed in class today: "For H-atom the electron is confined to its nuclear diameter, 1.7x10^-15m." He stated that this number would be the electron's uncertainty in position (delta x) in the Heisenberg and I am just slightly con...
Mon Oct 14, 2019 1:18 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Question
Replies: 3
Views: 51

### Re: Uncertainty Question

In Dr. Lavelle's lecture today (Monday), he showed a great example of a baseball being hit by photons and continuing on its pathway and then compared it to an electron going through the same thing. Since the mass of the baseball is so large, it has little to no uncertainty and effect in its velocity...
Sun Oct 06, 2019 11:35 pm
Forum: Molarity, Solutions, Dilutions
Topic: E.15
Replies: 2
Views: 108

### Re: E.15

After doing what the previous person stated, combine the unknown metal that you found with S to make it MS, and then find the molar mass of that compound for the answer! :)
Sun Oct 06, 2019 11:30 pm
Forum: Limiting Reactant Calculations
Topic: Net Ionic Equation
Replies: 6
Views: 136

### Re: Net Ionic Equation

Yes, a net ionic equation is basically everything the previous reply stated. Just wanted to add that the net ionic equation is not the full equation-- it is the equation after removing the "spectator ions", or the ions that are basically useless in forming the desired product and do not ta...
Sun Oct 06, 2019 11:27 pm
Forum: Limiting Reactant Calculations
Topic: Different Way to Find the Limiting Reactant
Replies: 3
Views: 108

### Re: Different Way to Find the Limiting Reactant

Thank you this is actually very helpful! Just curious, but I don't believe this method works if the problem just gives you the number of grams of each reactant? (Or it just wouldn't be as simple and straightforward)