## Search found 118 matches

Fri Mar 13, 2020 8:30 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7E.7
Replies: 2
Views: 41

### Re: 7E.7

It is also a different pathway because atoms in the transition state complex may have a different orientation, so the reactants take a different pathway to become the final products.
Fri Mar 13, 2020 8:28 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy vs Free Energy of Activation
Replies: 6
Views: 112

### Re: Activation Energy vs Free Energy of Activation

Activation energy can change for the reaction but I think free energy stays the same regardless of whether the activation energy is lower or higher.
Fri Mar 13, 2020 8:26 am
Forum: Second Order Reactions
Topic: 7B.17
Replies: 2
Views: 57

### Re: 7B.17

For the first part you can just use the numbers for [A] with the above equation. For part b, you would use the fact that delta[A]/delta t = 1/2 delta[B]/delta t. using that you can find out how much [A] changes as [B] increases to 0.19M. You can then use the above equation using [A]0 and [A] when [B...
Fri Mar 13, 2020 7:30 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7A.17
Replies: 2
Views: 63

### Re: 7A.17

Make sure to convert from mmol to mol before getting the final answer in mmol.
Fri Mar 13, 2020 7:29 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative overall order
Replies: 4
Views: 92

### Re: Negative overall order

Can the whole reaction have a negative overall order or only certain steps?
Fri Mar 13, 2020 7:25 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: K
Replies: 3
Views: 56

### Re: K

k doesn't have to have units M/s, but the overall rate does.
Sun Mar 08, 2020 12:31 pm
Forum: General Rate Laws
Topic: slow step
Replies: 9
Views: 112

### Re: slow step

I think the book said something like this:
- if the slow step is the second step, the rate law for that step determines the rate law for the reaction
- if the slow step is the first step, the rate law for that step must match the rate law for the reaction
Sun Mar 08, 2020 12:26 pm
Forum: First Order Reactions
Topic: 7B#3
Replies: 1
Views: 48

### Re: 7B#3

Yes, I think the negative is just because we flipped the final and initial. Also, remember that it's ln[final/initial] and not ln[final]/ln[initial].
Sun Mar 08, 2020 12:17 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: factors that affect k
Replies: 8
Views: 212

### Re: factors that affect k

A higher concentration of initial reactant usually indicates higher k as well.
Sun Mar 08, 2020 12:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L7 (b) HW
Replies: 3
Views: 75

### Re: 6L7 (b) HW

I think O2 is an intermediate that we see cancels out of the final chemical equation.
Tue Mar 03, 2020 11:38 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: HW 6.63
Replies: 1
Views: 38

### HW 6.63

The problem: When a pH meter was calibrated with a boric acid-borate buffer with a pH of 9.40, the cell potential was +0.060V. When the buffer was replaced with a solution of unknown hydronium ion concentration, the cell potential was +0.22V. What is the pH of the solution? My question: When using t...
Thu Feb 27, 2020 9:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 4L.7(a) - separating states in cell diagrams
Replies: 1
Views: 65

### 4L.7(a) - separating states in cell diagrams

For the reaction AgBr (s) <-- --> Ag+ (aq) + Br- (aq), why do you separate Ag(s) and AgBr(s) by a line in the cell diagram if they're both solids?
Thu Feb 27, 2020 9:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L7 (b) HW
Replies: 3
Views: 75

### Re: 6L7 (b) HW

Yeah I was a bit confused about how the oxidation numbers don't change, but it can be broken down to reduction and oxidation half reactions:

reduction: 4e- + O2 + 2H2O --> 4OH-
oxidation: 2H2O --> 4H+ + O2 + 2e-
Thu Feb 27, 2020 4:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Common Solutions in Salt Bridges
Replies: 2
Views: 26

### Common Solutions in Salt Bridges

What are some common solutions that are used to form salt bridges?
Thu Feb 27, 2020 4:06 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: log vs. ln in Nernst
Replies: 2
Views: 46

### log vs. ln in Nernst

What was Dr. Lavelle saying in lecture about showing an exponential relationship vs. a linear relationship using the Nernst equation? I think it was right after he talked about log/ln.
Sun Feb 23, 2020 5:40 pm
Forum: Balancing Redox Reactions
Topic: Half Reactions
Replies: 12
Views: 188

### Re: Half Reactions

An example of some half reactions would be:

Zn(s) --> Zn2+(aq)
Cu2+(aq) --> Cu (s)
Sun Feb 23, 2020 5:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potential
Replies: 4
Views: 71

### Re: Standard Cell Potential

If you keep each half-reaction as it is and just flip the cell diagram, then you know:
- if the right-hand electrode in the cell diagram is the cathode, you have a positive cell potential
- if the right-hand electrode in the cell diagram is the anode, you have a negative cell potential
Sun Feb 23, 2020 5:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Identify the state
Replies: 3
Views: 45

### Re: Identify the state

The element/compounds are expected to be written in a state that is in accordance with how it exists in nature. For instance, if you need to write H2, you know it will be a gas.
Sun Feb 23, 2020 5:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: neg vs pos
Replies: 9
Views: 62

### Re: neg vs pos

A positive voltage is associated with a positive Ecell, which means that a reaction has more pushing and pulling power to generate a high potential difference.
Sun Feb 23, 2020 5:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical series diagram
Replies: 2
Views: 24

### Re: Electrochemical series diagram

I think it means to reduce H+ to H2 gas.
Tue Feb 11, 2020 1:18 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal irreversible reactions
Replies: 3
Views: 57

### Isothermal irreversible reactions

Is the delta U of an isothermal irreversible reaction also equal to 0, like it is for an isothermal reversible reaction? If it's not equal to 0, why is that?
Tue Feb 11, 2020 1:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4.15
Replies: 1
Views: 47

### Re: Homework 4.15

You can then calculate the delta H of this reaction using enthalpy of formations and the fact that zinc is the limiting reactant. This delta H will be equal to the heat gained/lost from the HCl solution, and from there, the only variable you are missing is the final temperature, so you can directly ...
Tue Feb 11, 2020 1:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: how to find a heat capacity when not given
Replies: 3
Views: 42

### Re: how to find a heat capacity when not given

Usually it should be given, but if it's an ideal gas, Cv = (3/2)R and Cp = (5/2)R
Tue Feb 11, 2020 12:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp vs. Cv for ideal gas
Replies: 1
Views: 50

### Cp vs. Cv for ideal gas

If the problem only gives temperatures and doesn't specify anything about constant volume or pressure, how do you know whether you should use Cp or Cv?
Tue Feb 11, 2020 12:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4.17E: Calculating enthalpy change vs. assuming delta U = 0
Replies: 2
Views: 61

### 4.17E: Calculating enthalpy change vs. assuming delta U = 0

For the reaction 2SO2(g) + O2(g) --> 2SO3 (g), part c says to assume that temperature of the reaction remains constant. Part D asks to calculate work and Part E asks for enthalpy. Since temperature is constant, wouldn't the change in internal energy be zero? That's what I thought but the solutions m...
Thu Feb 06, 2020 10:30 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Question 4.37
Replies: 2
Views: 34

### Re: Question 4.37

I think delta(entropy of system) tells us about the spontaneity. If the entropy change is positive, it's spontaneous, but if the entropy change is negative, it isn't spontaneous. delta(entropy total) doesn't tell us about spontaneity because the total entropy should usually be positive since the ent...
Thu Feb 06, 2020 10:09 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: HW 4F.9
Replies: 2
Views: 33

### Re: HW 4F.9

You can use the pressures to determine the ratio of V2/V1, which is all you need to plug in to the equation.
Thu Feb 06, 2020 10:05 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4F12
Replies: 3
Views: 22

### Re: 4F12

The first equation is for a process where temperature changes and for the second equation, I think you mean volume instead of temperature, so that would be for an isothermal process.
Thu Feb 06, 2020 9:57 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Decreasing, Temperature Increasing
Replies: 6
Views: 58

### Re: Entropy Decreasing, Temperature Increasing

Entropy doesn't decrease with temperature, but the entropy change decreases with higher temperature. This is because a change to a lower temperature system will affect it more drastically than it would affect the higher temperature system, since it already has a higher entropy.
Thu Feb 06, 2020 9:45 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat capacity
Replies: 4
Views: 41

### Re: Heat capacity

For an ideal gas, Cv = (3/2)R and Cp = (5/2)R.
Thu Jan 30, 2020 12:05 pm
Forum: Calculating Work of Expansion
Topic: Irreversible vs. Reversible Reactions
Replies: 6
Views: 66

### Re: Irreversible vs. Reversible Reactions

During a reversible reaction, a small infinitesimal change can immediately affect the movement of the piston and reversing that small change would also reverse the movement of the piston.
Thu Jan 30, 2020 12:02 pm
Forum: Calculating Work of Expansion
Topic: Reversible processes and greatest work
Replies: 3
Views: 35

### Reversible processes and greatest work

Why do reversible processes do the greatest amount of work?
Thu Jan 30, 2020 12:00 pm
Forum: Calculating Work of Expansion
Topic: Integral
Replies: 4
Views: 46

### Re: Integral

I think you should just know that an integral is used to sum a series of steps, and in this case infinitesimal changes. It's basically the area under a curve, so the reason we use it to sum up infinitesimal changes is so we can sum the change in a pressure/volume curve.
Thu Jan 30, 2020 11:28 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Thermal Equilibrium
Replies: 1
Views: 17

### Thermal Equilibrium

In what cases would we have thermal equilibrium, where temperatures of system and surroundings are the same and energy flows as heat in both directions at the same rate?
Thu Jan 30, 2020 11:12 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.9
Replies: 4
Views: 54

### Re: 4A.9

Yeah, you can do (Tfinal - 100) and then add a negative sign to the other side with water to show that the heat lost by copper is that gained by water.
Sun Jan 26, 2020 11:33 am
Forum: Phase Changes & Related Calculations
Topic: motion of atoms
Replies: 2
Views: 24

### Re: motion of atoms

Not sure what context you're referring to, but maybe orderly vs. disorderly is just a way to assess the phase the molecules are in. So a solid would have more orderly motion of atoms, while a gas would have more disorderly motion of atoms.
Sun Jan 26, 2020 11:31 am
Forum: Phase Changes & Related Calculations
Topic: thermochemistry vs thermodynamics
Replies: 2
Views: 26

### Re: thermochemistry vs thermodynamics

Based on the outlines, in thermochemistry it seems like we'll mostly be discussing enthalpy, heat, and work in reactions, while in thermodynamics we'll also start learning about entropy and free energy.
Sun Jan 26, 2020 11:27 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: L.atm to Joules
Replies: 2
Views: 39

### Re: L.atm to Joules

Technically, yes. Use whichever is most convenient considering the units you have in the rest of your equation.
Sun Jan 26, 2020 11:25 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state functions and properties
Replies: 11
Views: 2621

### Re: state functions and properties

A good way to think about it is with the mountain example Dr. Lavelle presented in class: - altitude is a state function, as the height of an object does not depend on the path taken to get there - work is not a state function, as it depends on the energy taken to get there, so someone who took a lo...
Sun Jan 26, 2020 11:24 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4A.1
Replies: 12
Views: 75

### Re: 4A.1

Closed systems cannot exchange matter, but can exchange energy with their surroundings. Isolated systems are completely isolated and both matter and energy are constant.
Wed Jan 15, 2020 3:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic and Exothermic Reactions Class Example
Replies: 5
Views: 61

### Re: Endothermic and Exothermic Reactions Class Example

Since N2 is more stable, it's triple bond is pretty strong. Breaking that bond requires the addition of heat, while forming bonds releases heat. In this example, the product has a higher enthalpy (or energy) so the enthalpy change is positive, and thus, the reaction is exothermic.
Wed Jan 15, 2020 3:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I29
Replies: 2
Views: 46

### Re: 5I29

Yes, remember that when we were learning about Kc and Kp, when we were asked to find just K in general we could use concentration or pressure depending on what was given. The same goes here.
Wed Jan 15, 2020 3:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conjugate Seesaw and Kw
Replies: 3
Views: 50

### Re: Conjugate Seesaw and Kw

We add the two expressions together so that we are left with the equation for the autoprotolysis of water. Prof. Lavelle used NH3 and NH4+ to demonstrate the relationship between Ka and Kb for a base and its conjugate acid, and ultimately he derived the equation that relates Ka, Kb, and Kw. This is ...
Wed Jan 15, 2020 3:18 pm
Forum: Ideal Gases
Topic: mole fraction
Replies: 4
Views: 44

### Re: mole fraction

Yes, because as we see in Kc vs. Kp, concentration and pressure work about the same way. Just like how moles make up a certain fraction of total moles, partial pressure make up a certain fraction of total pressure.
Wed Jan 15, 2020 3:16 pm
Forum: Ideal Gases
Topic: Ideal Gas Law
Replies: 5
Views: 67

### Re: Ideal Gas Law

Use it any time you think you need to obtain anything included in the equation (pressure, volume, moles, temperature), but aren't given values for one or more of the components of the equation.
Wed Jan 08, 2020 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.11
Replies: 2
Views: 30

### Re: 5G.11

Hg is in pure liquid form and we've been told to only use what is aqueous or gaseous for Kc and Kp, as changes in amount of liquid are usually not quantitatively significant.
Wed Jan 08, 2020 9:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.35
Replies: 4
Views: 62

### Re: 5.35

I'm not completely sure about my reasoning for this, but the balanced equation might be 2A <-- --> B + 2C. A and C decrease and increase respectively at the same rate, and C increases twice as fast as B. Then you would just use the pressure where they each end on the graph and insert that into the K...
Wed Jan 08, 2020 9:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Multiples of Chemical Equation
Replies: 3
Views: 39

### Re: Multiples of Chemical Equation

I believe it still would because multiplying a chemical equation by any factor should raise K to that power.
Wed Jan 08, 2020 9:15 pm
Forum: Ideal Gases
Topic: PV=nRT equation manipulation
Replies: 13
Views: 232

### Re: PV=nRT equation manipulation

If you manipulate the equation to solve for P or concentration, then you can use the resulting pressure or concentration in when calculating Kc (concentration) or Kp (pressure).
Wed Jan 08, 2020 9:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 5G.1b
Replies: 1
Views: 34

### Re: Problem 5G.1b

I think it does mean that the concentration of products is increased at equilibrium, so yes the reaction would shift to the left to reach equilibrium.
Thu Dec 05, 2019 11:07 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Deciding shape
Replies: 3
Views: 119

### Deciding shape

How do you decide if a coordination compound is tetrahedral, octahedral, square planar, etc. when you have a compound that is the result of a transition metal reacting with water? For example, in 6D.11, Al3+ and Cu2+ form octahedral coordination compounds, but how do we determine this?
Thu Dec 05, 2019 11:04 pm
Forum: Lewis Acids & Bases
Topic: Hw 6.5
Replies: 4
Views: 73

### Re: Hw 6.5

In the solutions manual, why is SO3 drawn as having 1 double bond and 2 single bonds instead of 3 double bonds?
Thu Dec 05, 2019 3:21 pm
Forum: Biological Examples
Topic: EDTA
Replies: 3
Views: 94

### Re: EDTA

005162520 wrote:How does EDTA remove deadly metals from the bloodstream?

EDTA is a hexadentate ligand that can bind to metals, so by binding to metals, the metal cations are no longer floating freely in the bloodstream.
Thu Dec 05, 2019 2:53 pm
Forum: Biological Examples
Topic: Cisplatin binding
Replies: 1
Views: 50

### Cisplatin binding

How does the lone pair of the guanine bind to cisplatin? Does it bind to the chlorines of cisplatin? Or is the chlorine displaced by nitrogen or water?
Thu Dec 05, 2019 2:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 6
Views: 77

### Re: coordination number

The coordination number is just the number of bonds formed. So for A, the answer would be 4 bonds because 4 chlorines are bonded to one nickel atom.
Thu Dec 05, 2019 2:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: water
Replies: 3
Views: 64

### Re: water

Monodentate means a ligand can bind at one site and donate one electron pair. In the structure of water, both electron pairs are on a single central oxygen atom. That same oxygen atom cannot simultaneously bind to two sites, so water must be monodentate.
Thu Dec 05, 2019 2:35 pm
Forum: *Crystal Field Theory
Topic: Electric Field
Replies: 5
Views: 1548

### Re: Electric Field

brennayoung wrote:Does anyone know if this will be on the final?

I don't think we discussed it in class, so I don't think so.
Thu Dec 05, 2019 2:30 pm
Forum: Industrial Examples
Topic: Which examples?
Replies: 3
Views: 132

### Re: Which examples?

In addition to what's on the outlines, also the examples he introduced in lecture. Like cisplatin, hemoglobin, myoglobin, etc.
Fri Nov 29, 2019 1:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: polydentate and shape
Replies: 3
Views: 47

### polydentate and shape

How should we take molecular shape into account when deciding how many binding sites a polydentate ion has?
Fri Nov 29, 2019 1:06 pm
Forum: Naming
Topic: Naming Convention of Metal Anions
Replies: 5
Views: 61

### Re: Naming Convention of Metal Anions

If we do use the -ate, would be cobate or cobaltate?
Fri Nov 29, 2019 12:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Compound Naming
Replies: 1
Views: 30

### Re: Compound Naming

K4 [Ni(N)4] The potassium is outside the brackets, so the name will start with potassium. The transition metal name goes at the end. Did you intend for the ligand to be CN or is it just N? Not sure how to do it with N, but for CN, you would do potassium tetracyanidonickelate(IV). Try going about the...
Fri Nov 29, 2019 12:04 pm
Forum: Hybridization
Topic: Unhybridized Orbitals
Replies: 1
Views: 28

### Re: Unhybridized Orbitals

I'm not completely sure about this, but won't s orbitals never be unhybridized? S orbitals seem to always be involved in hybridization - sp, sp2, sp3, sp3d, etc. so extra electrons will go in unhybridized p orbitals.
Fri Nov 29, 2019 12:02 pm
Forum: Hybridization
Topic: Hybridization for elements like S, Xe, Br, etc.
Replies: 4
Views: 94

### Hybridization for elements like S, Xe, Br, etc.

How does hybridization work for elements where some or all of the valence electrons are paired? Do the paired electrons get promoted to d orbitals?
Fri Nov 29, 2019 11:54 am
Forum: Sigma & Pi Bonds
Topic: Need to Know
Replies: 3
Views: 80

### Re: Need to Know

I think you should also know what types of orbitals form each. For example, in ethene (C2H4), there are 4 sigma bonds between 1s and 2sp2, 1 sigma bond between 2sp2 and 2sp2, and 1 pi bond between the unhybridized p orbitals.
Fri Nov 29, 2019 11:34 am
Forum: Hybridization
Topic: Hybridization in Pi Bonds
Replies: 4
Views: 109

### Re: Hybridization in Pi Bonds

A pi bond is formed when two p-orbitals overlap side to side. When C double bonds with C as in ethylene, the C atom has sp2 hybridization, leaving one unhybridized p-orbital with 3 hybridized sp orbitals. These sp orbitals form sigma bonds with other atoms while the unhybridized p-orbital of one C ...
Fri Nov 29, 2019 11:28 am
Forum: Hybridization
Topic: Reason for 1 sigma and multiple pi bonds
Replies: 3
Views: 38

### Reason for 1 sigma and multiple pi bonds

How come when you have a double or triple bond, there is only one sigma bond and the rest are pi bonds?
Thu Nov 21, 2019 10:01 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: induced-dipole-induced-dipole VS. dipole-dipole in gas
Replies: 2
Views: 51

### induced-dipole-induced-dipole VS. dipole-dipole in gas

Why are induced-dipole-induced-dipole forces just as strong as dipole-dipole forces in a gas?
Thu Nov 21, 2019 9:58 am
Forum: Student Social/Study Group
Topic: Lydon's Week 8 Learning Session
Replies: 4
Views: 151

### Re: Lydon's Week 8 Learning Session

For 26b, how does size of the atoms impact bond angles?
Thu Nov 21, 2019 8:36 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Comparing Strength of Hydrogen Bonds
Replies: 1
Views: 39

### Comparing Strength of Hydrogen Bonds

If you have 2 molecules with hydrogen bonding, how can you tell which one is stronger?
Wed Nov 20, 2019 9:09 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: London forces vs. dipole-dipole for halogen-containing molecules
Replies: 3
Views: 50

### Re: London forces vs. dipole-dipole for halogen-containing molecules

To expand upon @Brittney Hun 1K and clarify a couple of things, both CHF 3 and CHI 3 exhibit dipole-dipole forces, so this doesn't matter in determining the melting/boiling points. What matters, therefore, is the LDFs of each molecule. CHI 3 is a larger molecule/has a higher molar mass, and this co...
Wed Nov 20, 2019 11:01 am
Forum: Sigma & Pi Bonds
Topic: Resonance Structures in 2F.3
Replies: 4
Views: 56

### Re: Resonance Structures in 2F.3

I was also confused about this. On the test, should we be drawing all resonance structures or just the most stable structure?
Wed Nov 20, 2019 10:59 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F19 Part C
Replies: 2
Views: 73

### 3F19 Part C

The boiling point of pentane - CH3(CH2)3 CH3 is 36.1 C, whereas that of C(CH3)4 is 9.5C. The solutions say that pentane has a higher surface area and thus stronger London forces than C(CH3)4 because C(CH3)4 is spherical and more compact, but how do you draw the lewis structure of C(CH3)4 to determin...
Wed Nov 20, 2019 10:56 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Intermolecular Forces
Replies: 6
Views: 119

### Re: Intermolecular Forces

Also the interactions between the atoms in the molecule. Pay attention to electronegativity to determine strength of dipole-dipole forces and whether hydrogen is in the molecule to determine if there are hydrogen bonds.
Wed Nov 20, 2019 10:53 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F.19
Replies: 5
Views: 129

### Re: 3F.19

Just to clarify, does high vapor pressure indicate higher boiling point?
Wed Nov 20, 2019 10:50 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F13
Replies: 6
Views: 200

### Re: 3F13

Make sure you aren't looking at each option as different angles of one molecule - that's why I was confused at first until I realized I needed to pay attention to intermolecular attractions and not intramolecular attractions!
Wed Nov 20, 2019 10:44 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: London forces vs. dipole-dipole for halogen-containing molecules
Replies: 3
Views: 50

### London forces vs. dipole-dipole for halogen-containing molecules

How do you determine which forces to prioritize when dealing with a molecule that has a halogen? For example, for 3F.5 part c, it says CHI3 has a higher melting/boiling point than CHF3 because of London forces. However, doesn't CHF3 have stronger dipole-dipole forces and aren't dipole-dipole forces ...
Wed Nov 20, 2019 10:40 am
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 3
Views: 52

### Re: Hydrogen Bonds

Hydrogen bonding is the dominant intermolecular force whenever N, O, or F is bonded to a hydrogen atom.
Sat Nov 16, 2019 4:45 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Electron configuration
Replies: 7
Views: 211

### Re: Electron configuration

Yes, the 4s orbital is lower energy than 3d, but once 4s is filled, it becomes higher energy than 3d, which is why electrons will be removed from 4s before 3d during ionization. So to clarify, if we need to remove electrons we would go to 4s before 3d, because this confused me. Yes, that is correct.
Sat Nov 16, 2019 4:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Structure of H2SeO4
Replies: 1
Views: 55

### Structure of H2SeO4

How would you draw dipole moment arrows for H2SeO4? Is this molecular polar and does the presence of the two hydrogen atoms affect its polarity?
Sat Nov 16, 2019 4:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octahedral Arrangement
Replies: 2
Views: 53

### Octahedral Arrangement

Why can't a central atom have more than 6 bonds/lone pairs? This allows for 12 electrons which is already an expanded octet, but why can't it expand more if the d subshell has 10 electrons and s, p, and d together have 18 electrons?
Sat Nov 16, 2019 4:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lewis structure of organic compunds
Replies: 5
Views: 78

### Re: lewis structure of organic compunds

You could try different orders of the atoms in the molecule and see which structure has the most favorable formal charges. For particularly long molecules, sometimes they group atoms attached to one another together. For example if you see CH3 or NH3 in a long molecular formula, you can likely assum...
Sat Nov 16, 2019 4:30 pm
Forum: Bond Lengths & Energies
Topic: Deep Potential Energy
Replies: 1
Views: 43

### Re: Deep Potential Energy

Chemical bonds store potential energy, so the higher the potential energy of a chemical bond (determined by the stability of the molecule --> lower potential energy = more stable molecule), the greater the dissociation energy because it will take more energy to break a higher energy chemical bond.
Sat Nov 16, 2019 4:26 pm
Forum: Ionic & Covalent Bonds
Topic: Types of Covalent Bonds
Replies: 4
Views: 53

### Re: Types of Covalent Bonds

The reason polar bonds are stronger is because the more electronegative atom attracts electrons of the other atom, shortening and strengthening the bond. As for coordinate covalent bonds, I think they are just as strong as any other covalent bond, but if someone else could confirm this that would be...
Sat Nov 16, 2019 4:21 pm
Forum: Ionic & Covalent Bonds
Topic: Polarity
Replies: 6
Views: 86

### Re: Polarity

It's important to note that the atoms in a molecule may have large differences in electronegativity, but the molecule itself still isn't polar because the dipole moments cancel. An example of this would be CCl4.
Tue Nov 05, 2019 7:51 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty in Position
Replies: 4
Views: 168

### Re: Heisenberg Uncertainty in Position

Yeah, I have the same question because I would think you'd multiply by 2 but I saw in one of the textbook question answers that they didn't...
Tue Nov 05, 2019 7:51 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Module Question
Replies: 2
Views: 77

### Re: Heisenberg Uncertainty Module Question

No, because if we know the mass of the object the uncertainty in velocity will be VERY miniscule.
Tue Nov 05, 2019 7:43 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg equation [ENDORSED]
Replies: 73
Views: 3929

### Re: Rydberg equation[ENDORSED]

For anyone confused about how the negative sign comes into play, you basically use the Rydberg equation to do Efinal - Einitial. So if an electron was going from n=1 to n=3, you'd do: -hR/9 - -hR/1
This would become positive, which makes sense because the electron is gaining energy.
Mon Nov 04, 2019 10:07 am
Forum: Photoelectric Effect
Topic: Threshold
Replies: 3
Views: 143

### Re: Threshold

It is not a constant value and may come with units like kJ/mol, so you can change it's value by changing the units.
Mon Nov 04, 2019 10:06 am
Forum: Photoelectric Effect
Topic: Work Function Units
Replies: 1
Views: 59

### Work Function Units

Sometimes the work function is given with units kJ/mol so you know to convert to J/atom, but what if no units are given? Should you assume you're given the energy to eject a mol or one electron?
Mon Nov 04, 2019 10:01 am
Forum: Formal Charge and Oxidation Numbers
Topic: Electron configuration
Replies: 7
Views: 211

### Re: Electron configuration

Yes, the 4s orbital is lower energy than 3d, but once 4s is filled, it becomes higher energy than 3d, which is why electrons will be removed from 4s before 3d during ionization.
Mon Nov 04, 2019 9:58 am
Forum: Formal Charge and Oxidation Numbers
Topic: Chlorine in center: electronegativity vs. formal charge
Replies: 4
Views: 94

### Chlorine in center: electronegativity vs. formal charge

What if the central atom is the most electronegative atom? (Ex. chlorine in the center in ClO4-) Would you want chlorine to be 0 or more negative than the oxygens since chlorine is more electronegative? What would the correct structure be for Cl04-? I've seen two different answers - one with 3 doubl...
Fri Nov 01, 2019 4:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d-orbital electrons and valence shell
Replies: 1
Views: 42

### d-orbital electrons and valence shell

How come d electrons usually aren't considered part of the valence shell? How come we usually just regard s2p6 as the valence electrons?
Fri Nov 01, 2019 4:09 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Configurations in 4d, 5d, etc. orbitals
Replies: 3
Views: 60

### Configurations in 4d, 5d, etc. orbitals

So we discussed that chromium and copper have exceptions in that they become 3d54s1 and 3d104s1. Does this also happen to elements in the same group as these two, like in 4d, 5d, etc?
Fri Nov 01, 2019 4:07 pm
Forum: Properties of Electrons
Topic: Diffraction patterns for neutrons
Replies: 1
Views: 53

### Diffraction patterns for neutrons

Since neutrons also show diffraction patterns after passing through a crystal, do they also have dual wave-particle properties? What about protons? How come their wave-particle duality isn't emphasized and we always focus on electrons?
Fri Nov 01, 2019 4:06 pm
Forum: DeBroglie Equation
Topic: Determining Wave-like Properties
Replies: 4
Views: 69

### Determining Wave-like Properties

How do you determine if an object has wave-like properties based on its mass and velocity? I know objects of high mass don't have significant wave-like properties, but for questions where you're asked to justify if a particular subatomic particle has wave-like properties, how would you justify it?
Fri Nov 01, 2019 3:58 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge vs Actual Charge
Replies: 2
Views: 52

### Re: Formal Charge vs Actual Charge

Yes, the formal charges on each atom adds up to the charge of the compound. I think it's a good way to check that your Lewis structure is correct. For example, if you have a chlorine in the center with a formal charge of +3, that is very unstable - especially since chlorine's usual anion has a -1 ch...
Fri Nov 01, 2019 3:51 pm
Forum: Trends in The Periodic Table
Topic: electron affinity and electronegativity
Replies: 2
Views: 41

### electron affinity and electronegativity

What are the similarities and differences between electron affinity and electronegativity?
Fri Nov 01, 2019 3:48 pm
Forum: Trends in The Periodic Table
Topic: s-block vs. p-block effective nuclear charge
Replies: 1
Views: 38

### s-block vs. p-block effective nuclear charge

so s electrons are found close to the nucleus and are therefore more tightly bound to the nucleus but p electrons (assume same principal energy level) have higher effective nuclear charge than s electrons because they have more protons and electrons Both of those statements seem contradictory, so co...
Sun Oct 27, 2019 10:20 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 4
Views: 54

Yeah, I saw that in the textbook too but he never mentioned it in class so I doubt it.
Sun Oct 27, 2019 10:17 am
Forum: Trends in The Periodic Table
Topic: Question on 1E.5
Replies: 2
Views: 25

### Question on 1E.5

For b, why are s electrons better at shielding than p electrons?

For d, how come effective nuclear charge is lower for p electrons than s electrons in the same shell? Doesn't higher effective nuclear charge = more protons, and p-orbital elements have higher atomic numbers?