Search found 100 matches

by Juliet Stephenson 4E
Sat Mar 14, 2020 10:38 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E vs Eo
Replies: 6
Views: 121

Re: E vs Eo

E0 represents Ecell at standard conditions.
by Juliet Stephenson 4E
Sat Mar 14, 2020 10:35 am
Forum: Balancing Redox Reactions
Topic: Oxidation number
Replies: 12
Views: 215

Re: Oxidation number

So what is the difference between oxidation number and the charge the atom carries? Charge says something about the relationship between the number of protons and electrons. Charge equals [Proton # - Electron #]. Oxidation numbers are more representations of the total number of electrons that an at...
by Juliet Stephenson 4E
Sat Mar 14, 2020 10:32 am
Forum: Second Order Reactions
Topic: Graphs
Replies: 7
Views: 105

Re: Graphs

Units of k also change for each order. Rate will always equal Moles/liter.seconds but since we are sometimes squaring or cubing concentration, K will have different units for each order. Most charts contain some reference to this.
by Juliet Stephenson 4E
Tue Mar 10, 2020 7:10 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 4
Views: 40

Re: Molecularity

Siddiq 1E wrote:does this mean molecularity corresponds with rate order?


I believe this is true. So reactions can be unimolecular (1st order), bimolecular (2nd order), or termolecular (3rd order).
by Juliet Stephenson 4E
Tue Mar 10, 2020 7:06 pm
Forum: Biological Examples
Topic: COVID-19
Replies: 6
Views: 149

Re: COVID-19

My friend's TA emailed and asked for students to email pictures of their week 10 homework, but I would wait for your TA to email you to be sure that they don't get flooded with emails.
by Juliet Stephenson 4E
Sun Mar 08, 2020 8:48 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Homework Problem 7.1
Replies: 1
Views: 23

Re: Homework Problem 7.1

At the lower temperature, when kinetics dominates, CH 3 CHBrCH=CH 2 is in a higher quantity. At the higher temperature, when thermodynamics dominates, CH 3 CH=CHCH 2 Br is in a higher quantity. The product formed at lower temperatures will have the lower activation energy, since it is forming as a r...
by Juliet Stephenson 4E
Sun Mar 08, 2020 8:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 10
Views: 64

Re: Platinum

What defines a solid conductor?
by Juliet Stephenson 4E
Sun Mar 08, 2020 8:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Diagram
Replies: 16
Views: 201

Re: Cell Diagram

Yes. I find it useful to remember that Reduction occurs on the Right in the Cathode (all consonants, two Rs) while Oxidation occurs in the Anode (vowels) on the left.
by Juliet Stephenson 4E
Sun Mar 08, 2020 8:36 pm
Forum: Balancing Redox Reactions
Topic: e- amount
Replies: 9
Views: 74

Re: e- amount

You need to multiply the reactions so that the number of moles of e- are the same and they will cancel out correctly.
by Juliet Stephenson 4E
Sun Mar 08, 2020 8:34 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: How to determine the order of a reactant
Replies: 3
Views: 59

Re: How to determine the order of a reactant

I don't think this is the easiest way, but one important distinction is that different orders have differently shaped graphs of concentration vs time. You can tell what the order is by observing which concentration vs. time graph is linear. For first order reactions, ln[A] vs. time is linear. For se...
by Juliet Stephenson 4E
Sun Mar 01, 2020 5:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic and Voltaic Cells
Replies: 1
Views: 33

Re: Galvanic and Voltaic Cells

Galvanic/Voltaic cells include spontaneous reactions and they release energy. I found this image helpful. Image
by Juliet Stephenson 4E
Sun Mar 01, 2020 5:27 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Equations
Replies: 2
Views: 52

Re: Equations

Which equation are you referring to?
by Juliet Stephenson 4E
Sun Mar 01, 2020 5:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical Series
Replies: 3
Views: 38

Re: Electrochemical Series

I think the electrochemical series is a sort of list of reactions that allows us to classify elements or molecules in order of their reduction potentials, but outside of this I am not really sure what we need to know.
by Juliet Stephenson 4E
Sun Mar 01, 2020 5:21 pm
Forum: First Order Reactions
Topic: Order of the Reaction
Replies: 2
Views: 49

Order of the Reaction

What exactly does the order of the reaction mean and how do we determine it? I read in my notes that it is equivalent to the number of molecules of the reactant which are colliding during the slowest step of the reaction, but I feel like I'm missing some context.
by Juliet Stephenson 4E
Sun Mar 01, 2020 5:11 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: electrolysis
Replies: 6
Views: 77

Re: electrolysis

Yes, the reaction will be electrolyzed to allow it to proceed when it cannot otherwise proceed because it is non-spontaneous.
by Juliet Stephenson 4E
Sun Feb 16, 2020 6:29 pm
Forum: Balancing Redox Reactions
Topic: Half reactions
Replies: 7
Views: 71

Re: Half reactions

ng1D wrote:When balancing redox reactions, are we balancing the number of atoms or electrons?

Both!
by Juliet Stephenson 4E
Sun Feb 16, 2020 6:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Autoprotolysis
Replies: 6
Views: 129

Re: Autoprotolysis

Yes! After doing a little internet research I found that, generally, a substance containing both hydrogen bonds and lone pairs can potentially experience autoprotolysis. For example, ammonia and acetic acid can both experience autoprotolysis.
by Juliet Stephenson 4E
Sun Feb 16, 2020 6:20 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Delta E
Replies: 11
Views: 197

Re: Delta E

Delta E and Delta U both represent the change in internal energy in a system. Both values are equal to the Final Energy of the System-Initial Energy of the System.
by Juliet Stephenson 4E
Sun Feb 16, 2020 6:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8017
Views: 1403377

Re: Post All Chemistry Jokes Here

Q: What is the chemical formula for a banana?
A: BaNa2
by Juliet Stephenson 4E
Sun Feb 16, 2020 6:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Volume of the Universe
Replies: 4
Views: 54

Re: Volume of the Universe

Yes, I would say this is a correct assumption.
by Juliet Stephenson 4E
Sun Feb 09, 2020 10:58 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal Irreversible
Replies: 3
Views: 28

Re: Isothermal Irreversible

I agree! I believe isothermal expansions are irreversible because they progress towards a uniform state, which is an irreversible change.
by Juliet Stephenson 4E
Sun Feb 09, 2020 10:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A11
Replies: 3
Views: 40

Re: 4A11

It looks like you're using 25 kJ as the value for qcal but it should be 22.5 kJ.
by Juliet Stephenson 4E
Sun Feb 09, 2020 10:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Intensive
Replies: 8
Views: 102

Re: Intensive

For these questions, I find it really helpful to imagine a glass half-full of water. For this glass, as for any system, you would be able to assign specific values to different properties. If, by filling the glass up all the way, one of these values would change, then that corresponding property is ...
by Juliet Stephenson 4E
Sun Feb 09, 2020 10:33 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: q rev
Replies: 4
Views: 56

Re: q rev

A process is reversible if the system maintains thermodynamic equilibrium with its surroundings throughout the whole process. Reversible processes are less common than irreversible processes, and a perfectly reversible process is not possible.
by Juliet Stephenson 4E
Sun Feb 09, 2020 3:57 pm
Forum: Administrative Questions and Class Announcements
Topic: memorizing things?
Replies: 13
Views: 124

Re: memorizing things?

I am at Lyndon's review session and he said we won't be provided the equation for degeneracy (W=# of microstates# of particles), so be sure to memorize that!
by Juliet Stephenson 4E
Sun Feb 09, 2020 9:53 am
Forum: Calculating Work of Expansion
Topic: Irreversible Expansion Explained
Replies: 7
Views: 95

Re: Irreversible Expansion Explained

This is kind of irrelevant to the question but will the question always say if it is reversible or irreversible? Or is there another way we will know which equation to use? I am pretty sure the question will always say whether the expansion is reversible or irreversible. I am not aware of a way we ...
by Juliet Stephenson 4E
Sun Feb 09, 2020 9:50 am
Forum: Administrative Questions and Class Announcements
Topic: memorizing things?
Replies: 13
Views: 124

Re: memorizing things?

I don't think there are any values we need to memorize for this midterm. It is always very helpful to me to go over the constants and equations sheet before exams as a little study guide of sorts. We don't know how to use all of the equations yet, but it is still a helpful review of some of the topi...
by Juliet Stephenson 4E
Sun Feb 09, 2020 9:46 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Equipartition Therom
Replies: 3
Views: 40

Re: Equipartition Therom

Parts of it seemed familiar to me from lecture, so I would guess we are responsible for knowing the fundamentals of that section. It is definitely included in the reading assignment as well.
by Juliet Stephenson 4E
Sun Feb 02, 2020 3:49 pm
Forum: Calculating Work of Expansion
Topic: Hw 4A.13
Replies: 2
Views: 29

Re: Hw 4A.13

Hi Amy! I found example 4A.4 in the book on page 253 to be super helpful in walking me through this problem. I would highly recommend looking at it. In summary, first use Ccal=qcal/deltaT and then use your Ccal value to find q using q=-Ccal * deltaT.
by Juliet Stephenson 4E
Sun Feb 02, 2020 3:16 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: self test 4A.1A
Replies: 2
Views: 31

Re: self test 4A.1A

The first time I did this problem is ended up with -.86 kJ but it was because I made an error (multiplied mass times density instead of dividing). I am thinking the answer key is wrong. I don't think such a large discrepancy could be produced by premature rounding.
by Juliet Stephenson 4E
Sun Feb 02, 2020 2:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Elements
Replies: 8
Views: 41

Re: Elements

Since O2 and other diatomics are so stable, they tend to form in nature. As a result, there is no enthalpy of formation, as oxygen will already be in this form.
by Juliet Stephenson 4E
Sun Feb 02, 2020 2:05 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Extensive vs. intensive property
Replies: 3
Views: 47

Re: Extensive vs. intensive property

An extensive property is a property that depends on the amount of a substance that is present in a sample. For example, the mass of a substance changes depending on how much of the substance you are measuring, so it is an extensive property. An intensive property is a property that stays the same re...
by Juliet Stephenson 4E
Sun Feb 02, 2020 1:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 4
Views: 70

Re: Systems

An open system is not contained, and as a result can lose or gain mass or energy during the course of a reaction. A closed system is contained (and therefore cannot lose or gain mass during the course oof a reaction) but can still transfer or receive energy to/from the environment. An isolated syste...
by Juliet Stephenson 4E
Sun Jan 26, 2020 4:14 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Change
Replies: 4
Views: 41

Re: Phase Change

I also think it would be possible that we would have to calculate the phase change enthalpy for sublimation based on given values of vaporization and fusion.
by Juliet Stephenson 4E
Sun Jan 26, 2020 4:09 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy vs. Energy
Replies: 2
Views: 38

Re: Enthalpy vs. Energy

Energy is the ability to do work, and is usually expressed in joules. Enthalpy is more specific - the ability of a certain material to do work, usually expressed in joules per mass unit (gram, kg, etc).
by Juliet Stephenson 4E
Sun Jan 26, 2020 4:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Preferences between Methods
Replies: 3
Views: 32

Re: Preferences between Methods

The method you should use depends on the information provided in the problem.
by Juliet Stephenson 4E
Sun Jan 26, 2020 3:52 pm
Forum: Phase Changes & Related Calculations
Topic: state functions
Replies: 3
Views: 35

Re: state functions

Since state functions are based on the end state of a system, they can be added without concern. This is because they represent a specific phase/time after the reaction has reached equilibrium.
by Juliet Stephenson 4E
Sun Jan 26, 2020 3:43 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy & Spontaneity
Replies: 4
Views: 47

Re: Enthalpy & Spontaneity

An endothermic reaction can only occur when there is excess free energy in the environment, while an exothermic reaction can occur in the absence of this energy. Therefore, the larger the deltaH value, the less spontaneously the reaction will occur.
by Juliet Stephenson 4E
Sun Jan 19, 2020 12:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 4
Views: 30

Re: ICE Box

Since the concentration isn't changing, [H2O] will appear in the numerator and the denominator, so it will be equivalent to one and have no affect on the equilibrium constant. Therefore, it makes the most sense to just exclude it from your calculations altogether.
by Juliet Stephenson 4E
Sun Jan 19, 2020 12:06 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Counting Moles when Compression occurs
Replies: 2
Views: 27

Re: Counting Moles when Compression occurs

I think you would exclude the solid, because it will not be affected by a pressure change. A solid is already in the most compressed state it can be in, so increasing the pressure won't have any effect on the concentration. Increasing pressure will only affect the solid in the way that the solid is ...
by Juliet Stephenson 4E
Sun Jan 19, 2020 12:01 pm
Forum: Identifying Acidic & Basic Salts
Topic: Identifying salts
Replies: 2
Views: 82

Re: Identifying salts

Salts form when an anion (Cl-, for example) and a cation (Na+, for example) form a compound in a substance. Whenever an acid reacts with a base, salts are formed.
by Juliet Stephenson 4E
Sun Jan 19, 2020 11:49 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 5
Views: 41

Re: Pressure

When there is increased pressure, the reaction will favor whichever direction has fewer moles of product. For example, for the reaction Cl 2 <-> 2Cl, if the pressure were increased at equilibrium, the reverse reaction would be favored since there is only one mole of Cl 2 for every two moles of 2Cl.
by Juliet Stephenson 4E
Sun Jan 19, 2020 11:47 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different Values for K and Kc?
Replies: 3
Views: 42

Different Values for K and Kc?

In Table 5G.2, a list of equilibrium constants for various reactions are provided. For many reactions, K and Kc have the same value, which I would expect based on the fact that these two constants are calculated in the same way. However, for the bottom half of the table, K and Kc have different valu...
by Juliet Stephenson 4E
Sun Jan 12, 2020 9:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Dissociated Ionic Compounds
Replies: 5
Views: 50

Re: Dissociated Ionic Compounds

In regards to the activity of each ion, I believe they are referring to the ion's respective concentration. I hope this helps! That makes sense, in a problem would that value be given or is there a way to calculate it? it would likely be given but i guess if they did want us to calculate the ions' ...
by Juliet Stephenson 4E
Sun Jan 12, 2020 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.27
Replies: 8
Views: 75

Re: 5I.27

I think equilibrium composition might mean the concentrations of reactants and products at equilibrium but I am not certain.
by Juliet Stephenson 4E
Sun Jan 12, 2020 9:25 pm
Forum: General Science Questions
Topic: Proton and Electron attraction
Replies: 5
Views: 58

Re: Proton and Electron attraction

Protons and electrons are attracted to each other because protons are positively charged and electrons are negatively charged. Opposite charges always attract. In the structure of atoms, the presence of neutrons helps to stabilize the system.
by Juliet Stephenson 4E
Sun Jan 12, 2020 9:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Response of Equilibria to Change
Replies: 6
Views: 44

Re: Response of Equilibria to Change

The rule of thumb is that the equilibrium will respond in a way that counteracts the change. However, this doesn't give you an accurate representation, so the best way to do so is to recalculate using equations to determine equilibrium. Can you specify which equations we would use to recalculate? W...
by Juliet Stephenson 4E
Sun Jan 12, 2020 9:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q>K
Replies: 9
Views: 72

Re: Q>K

If one were to manually add products to a system at equilibrium, Q would be greater than K until the system rebalanced itself.
by Juliet Stephenson 4E
Sun Dec 08, 2019 9:40 pm
Forum: Administrative Questions and Class Announcements
Topic: FINAL
Replies: 7
Views: 183

Re: FINAL

I thought it was pretty difficult! I wasn't expecting there to be any titration problems because I thought I heard Lavelle said we wouldn't be doing it until 14B, so that really threw me off. In general there were a lot of things I wasn't sure about. I am still proud of how much I prepared for the e...
by Juliet Stephenson 4E
Fri Dec 06, 2019 9:23 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: HF
Replies: 4
Views: 151

Re: HF

HF is a weak acid because the H-F bond is incredibly strong due to the electronegativity of F and the small atomic radius of F. As a result, it has short bonds that aren't equally broken, which translates to low levels of dissociation.
by Juliet Stephenson 4E
Fri Dec 06, 2019 12:15 pm
Forum: Hybridization
Topic: Hybridization - 2F9 part d
Replies: 1
Views: 32

Hybridization - 2F9 part d

I feel like I have a pretty good handle on hybridization when there is electron promotion, but I am struggling to understand 2F9 part d. d) Find the hybrid orbitals used by PCl 3 . I know the solutions manual says it is sp 3 , but I am having a little trouble understanding why. The electron configur...
by Juliet Stephenson 4E
Fri Dec 06, 2019 3:16 am
Forum: Bronsted Acids & Bases
Topic: Amphiprotic vs amphoteric
Replies: 3
Views: 62

Re: Amphiprotic vs amphoteric

Amphiprotic (think proton) refers to a molecule that can donate or accept a proton. Of course, this means that it can act as both an acid and a base. Amphoteric means the same thing but the term is a little more general, whereas amphiprotic is referring to the specific idea of protonation/deprotonat...
by Juliet Stephenson 4E
Fri Dec 06, 2019 3:13 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate
Replies: 1
Views: 48

Re: Chelate

Something can form a chelating complex if it has a) more than one lone pair available for bonding (bidentate or polydentate) AND b) has those bonds close enough together to form a ring (i.e. they are on the same side of the molecule). A molecule that can form a chelating complex should have the stru...
by Juliet Stephenson 4E
Wed Dec 04, 2019 1:43 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 1
Views: 28

Re: Bronsted Acids and Bases

Bronsted acids and bases are actually concerned with the transfer of protons. Lewis acids and bases are concerned with the transfer of electron pairs. Bronsted acids are capable of donating a proton because the products of this reaction are more stable than the reactants. Bronsted acids produce Hydr...
by Juliet Stephenson 4E
Sun Dec 01, 2019 11:05 am
Forum: Polyprotic Acids & Bases
Topic: How can you tell
Replies: 11
Views: 272

Re: How can you tell

Each H present in the anion will go on to form one hydronium ion. In HCl, one H begets one hydronium ion per molecule HCl (monoprotic). In H2S04, two H's will beget two hydronium ions per molecule H2So4 (biprotic/polyprotic). This is important to remember in calculating the pH of a substance.
by Juliet Stephenson 4E
Sun Dec 01, 2019 11:01 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Reactions, Equilibrium
Replies: 4
Views: 46

Re: Reactions, Equilibrium

Given most chemical reactions (consider the dissolving of salt in water) reactions are proceeding in both directions at all times. In our saltwater example, NaCl is both being dissolved and reforming at all times. In most chemical reactions, one direction of the reaction takes more energy, and so no...
by Juliet Stephenson 4E
Sun Dec 01, 2019 10:54 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Textbook Problem 6B.1
Replies: 1
Views: 32

Re: Textbook Problem 6B.1

I would start by assigning an arbitrary value to your starting pH and then manipulating the values as the problem suggests. Since pH is a logarithmic scale, differences should be the same given any starting value.
by Juliet Stephenson 4E
Sat Nov 30, 2019 8:34 pm
Forum: Biological Examples
Topic: Coordination Compounds and Chemotherapy Drugs
Replies: 5
Views: 77

Re: Coordination Compounds and Chemotherapy Drugs

I can't remember what the full name of the compound is but the drug is called cisplatin, and if you feel like googling that, it should yield more information regarding the full name of the coordination compound.
by Juliet Stephenson 4E
Sat Nov 30, 2019 8:33 pm
Forum: Bronsted Acids & Bases
Topic: HBr
Replies: 3
Views: 39

Re: HBr

It is helpful for me to remember that if I'm writing out the dissociation of an acid, one of the products will usually be hydronium (H3O), and if I'm writing out the dissociation of a base, one of the products will be hydroxide (OH).
by Juliet Stephenson 4E
Sun Nov 24, 2019 11:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw shape
Replies: 5
Views: 59

Re: Seesaw shape

Seesaw shape occurs when you have a molecule with five areas of electron density, one being a lone pair. Normally, such a molecule would have a trigonal bipyramidal shape, but since the lone pair doesn't show up in our visualization of the shape, we can visualize the removal of one atom. This leaves...
by Juliet Stephenson 4E
Sun Nov 24, 2019 11:42 pm
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 21
Views: 151

Sigma and Pi Bonds

I am confused about how we can identify sigma and pi bonds in a molecule. Will someone please explain? Thank you!
by Juliet Stephenson 4E
Sun Nov 24, 2019 11:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Cis and Trans
Replies: 6
Views: 109

Re: Cis and Trans

I think it all has to do with the structure of whatever the molecule is binding to. If the main molecule features groups that are close together, then the attaching molecule would probably need to be cis.
by Juliet Stephenson 4E
Mon Nov 18, 2019 3:23 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: H-Bonds
Replies: 1
Views: 30

Re: H-Bonds

In Step-Up my UA advised that, while not incorrect to list both, it is only necessary to list hydrogen bonds.
by Juliet Stephenson 4E
Mon Nov 18, 2019 3:21 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: Dipole- induced dipole
Replies: 2
Views: 25

Re: Dipole- induced dipole

Yes, because if this type of intermolecular force were occurring between two of the same type of molecule they would either be dipole-dipole (in the case that the molecule is polar) or London dispersion (in the case that the molecule is nonpolar).
by Juliet Stephenson 4E
Sun Nov 17, 2019 11:40 pm
Forum: Ionic & Covalent Bonds
Topic: types of bonds
Replies: 4
Views: 74

Re: types of bonds

Yes. If we are talking about two different molecules binding to each other, then dipole-induced dipole is also possible.
by Juliet Stephenson 4E
Sun Nov 17, 2019 11:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 9
Views: 95

Re: Bond Angles

This chart from step up was really helpful for me. Besides that, I think if you just understand the shapes, you'll probably be able to figure out the angles just by dividing 360 by the number of bonds.
https://drive.google.com/file/d/1h2MnGaEAe2sEf8yZ96NREj_8hGNLmluw/view?usp=sharing
by Juliet Stephenson 4E
Sat Nov 16, 2019 5:58 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: strongest intermolecular forces
Replies: 7
Views: 104

Re: strongest intermolecular forces

When we're discussing two of the same molecules binding with each other, hydrogen bonds are the strongest, followed by dipole-dipole, followed by London dispersion/Van der Waals forces. Dipole-induced dipole interactions will only occur between two different molecules, usually a polar molecule and a...
by Juliet Stephenson 4E
Sun Nov 10, 2019 9:14 pm
Forum: Student Social/Study Group
Topic: chem 14b + cehm14bl
Replies: 9
Views: 154

Re: chem 14b + cehm14bl

I have always been advised by both peers and my department counselor not to take B and BL at the same time. BL is known for being pretty difficult and from what I understand, it depends on concepts which are taught in B, which can be a little tricky if you're figuring them out at the same time that ...
by Juliet Stephenson 4E
Sun Nov 10, 2019 9:07 pm
Forum: Dipole Moments
Topic: Dipole-Induced Dipole
Replies: 2
Views: 36

Re: Dipole-Induced Dipole

Induced-dipole-induced-dipole interactions occur when two molecules become dipoles by chance. They are not naturally dipoles, but because of their environment or just random variations in the electron clouds, they become dipoles and experience bonding. An example would be two molecules of the same a...
by Juliet Stephenson 4E
Sun Nov 10, 2019 9:00 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: Boiling point
Replies: 5
Views: 75

Re: Boiling point

The number of hydrogen bonds/induced-dipole-induced-dipole interactions also contribute to boiling points (as they also contribute to bond length/strength). I found Lavelle's example of A-T vs G-C bonding in DNA particularly helpful. Since A-T has dipole-dipole interactions at two sites, it has a lo...
by Juliet Stephenson 4E
Sun Nov 10, 2019 8:49 pm
Forum: Bond Lengths & Energies
Topic: Week 7 Homework
Replies: 15
Views: 226

Re: Week 7 Homework

Daniel Chen 1B wrote:But are we able to turn in homework from the Topic 2 section still?

I feel like we probably can't do problems from topic 2 anymore since all of last week was chemical bonds.
by Juliet Stephenson 4E
Sun Nov 10, 2019 8:48 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: Fluctuating Dipoles
Replies: 5
Views: 99

Re: Fluctuating Dipoles

I don't think we would have to illustrate this very often. Maybe we might have to use partial charges like we do with hydrogen bonds. Hopefully we will get more examples in class.
by Juliet Stephenson 4E
Sun Nov 03, 2019 9:05 pm
Forum: Octet Exceptions
Topic: Octet Rule exceptions
Replies: 14
Views: 320

Re: Octet Rule exceptions

Kevin Antony 1J wrote:H, He, Li, Be, B, and Al I believe will never have a full octet. Additionally, some elements like Si, P, S, and Cl can have expanded octets. I'm pretty sure we just have to memorize what the exceptions are.

What is the reasoning behind Al not being able to have a full octet?
by Juliet Stephenson 4E
Sun Nov 03, 2019 9:03 pm
Forum: Octet Exceptions
Topic: Octet Rule exceptions
Replies: 14
Views: 320

Re: Octet Rule exceptions

Hydrogen, Helium, Lithium, and Beryllium are exceptions because they only have s orbitals. Elements that are period 3+ can also potentially expand their octet.
by Juliet Stephenson 4E
Sun Nov 03, 2019 8:57 pm
Forum: Lewis Structures
Topic: Octet Rule
Replies: 6
Views: 76

Re: Octet Rule

The octet rule states that atoms tend to bond with each other in order to form a complete octet, meaning they have 8 total electrons in their outer shell.
by Juliet Stephenson 4E
Sun Nov 03, 2019 8:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: f-block
Replies: 2
Views: 46

Re: f-block

I feel like Lavelle was pretty firm about us not working with the F block in this course. My TA also told us it would not be featured in the course.
by Juliet Stephenson 4E
Sun Nov 03, 2019 8:43 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 5
Views: 60

Re: Expanded Octets

For the purposes of this class, 10 electrons, because that is how many can fit in the d orbital. But if we were working with the f orbital, I assume it would be more.
by Juliet Stephenson 4E
Wed Oct 30, 2019 1:30 am
Forum: Resonance Structures
Topic: 2B. 3
Replies: 2
Views: 41

Re: 2B. 3

This is a little tricky to type out but this is what I got. c) :O=Si=O: d) :F : : :F : : :Br: :F : : :F : : which is to say a Br surrounded by four F connected with single bonds. 2 sets of loan pairs around Br. This works because Br can have an expanded octet. If you calculate the formal charges, yo...
by Juliet Stephenson 4E
Sun Oct 27, 2019 6:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Thanksgiving
Replies: 3
Views: 67

Thanksgiving

Will we be having lecture on the Wednesday before Thanksgiving (Nov. 27th)? Will we be meeting in our discussion sections that day?
by Juliet Stephenson 4E
Sun Oct 27, 2019 5:18 pm
Forum: Electronegativity
Topic: Difference between electronegativity, ionization energy, and electron affinity
Replies: 5
Views: 84

Re: Difference between electronegativity, ionization energy, and electron affinity

Electronegativity is a measurement of an atom's attraction to electrons - its own as well as outside electrons. Ionization energy is the energy input required to remove an electron from an atom. Electron affinity is a measurement of change in the energy of an atom when an electron is added. Electron...
by Juliet Stephenson 4E
Sun Oct 27, 2019 2:25 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 4
Views: 47

Re: Valence Electrons

I found this table very helpful in understanding this concept.

Image

more info at https://socratic.org/questions/how-can-i-find-valence-electrons-of-transition-metals
by Juliet Stephenson 4E
Sun Oct 27, 2019 11:02 am
Forum: Trends in The Periodic Table
Topic: IE, EA, EN, AR Trends
Replies: 4
Views: 33

Re: IE, EA, EN, AR Trends

megan3j wrote:for IE, EA, EN: as you move to the right --> these increase; also as you move up the periodic table they increase
for AR: as you move to the left <-- the AR increases; as you move down the periodic table the AR inrcreases


Can you say what all of these stand for? Thanks!
by Juliet Stephenson 4E
Sun Oct 27, 2019 11:00 am
Forum: Resonance Structures
Topic: 'delocalized'
Replies: 4
Views: 52

Re: 'delocalized'

I always interpret this to mean that the electrons have a less precise location. Because they have multiple "possible" locations, we can't assign them a particular place in the octet or to a particular bond, so they are delocalized. The effect of this is that they create more stable bonds.
by Juliet Stephenson 4E
Sun Oct 27, 2019 10:56 am
Forum: Ionic & Covalent Bonds
Topic: P, Cl, and S octet tule exceptions
Replies: 4
Views: 52

Re: P, Cl, and S octet tule exceptions

These elements are all in the d block, which means they have access to extra orbitals in which they can store electrons.
by Juliet Stephenson 4E
Sun Oct 20, 2019 10:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Stern and Gerlach Experiment: Electron Spin
Replies: 3
Views: 34

Re: Stern and Gerlach Experiment: Electron Spin

Is there a good way to visualize spin? Are electrons actually spinning in the magnetic field? Or is it some other quality that can't be visualized?
by Juliet Stephenson 4E
Sun Oct 20, 2019 10:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Orbital energy levels
Replies: 1
Views: 28

Re: Orbital energy levels

Yes. Electrons in the S orbital are more effective at shielding, so an electron in the p orbital would experience less Zeffe.
by Juliet Stephenson 4E
Sun Oct 20, 2019 10:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why is copper like this?
Replies: 6
Views: 80

Re: Why is copper like this?

I just read something that said that violations to the aufbau principle are more common for elements with higher atomic numbers than for those with lower atomic numbers. Why is this? Hi Will, As was mentioned earlier in this thread, full and half-full subshells are rather stable and can have lower ...
by Juliet Stephenson 4E
Tue Oct 15, 2019 12:51 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Light's effects
Replies: 4
Views: 57

Re: Light's effects

I think its best to think of this as an effect of mass. The mass of a baseball is around .145 kg. The mass of an electron is around 9.109 * 10 -31 kg. Photons are massless, but they do have energy and are moving at very high speeds. A massless particle won't affect the position or momentum of someth...
by Juliet Stephenson 4E
Tue Oct 15, 2019 12:40 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: HW Problem 1.A.15
Replies: 3
Views: 62

Re: HW Problem 1.A.15

Can anyone walk me through this problem using En=-hR/n2? I understand how to do this using the Rydberg Equation, but am having trouble figuring it out the other way. Thank you!
by Juliet Stephenson 4E
Sun Oct 13, 2019 3:56 pm
Forum: Properties of Light
Topic: Threshold Energy
Replies: 2
Views: 43

Re: Threshold Energy

I would also add that, practically, work function is usually in different units than joules, so it usually takes a little bit of finagling to get it in the right units for the problem. Be sure to watch out for that! In my experience so far, when threshold energy is given, it is usually already in jo...
by Juliet Stephenson 4E
Sun Oct 13, 2019 3:50 pm
Forum: Properties of Electrons
Topic: Diffraction
Replies: 6
Views: 61

Re: Diffraction

Constructive interference occurs when the waves line up in-phase, so they stack on top of each other and gain energy (higher frequency, shorter wavelength). Destructive interference occurs when waves line up out of phase. Imagine that the peak of one wave is lining up with the trough of a different ...
by Juliet Stephenson 4E
Sun Oct 13, 2019 3:45 pm
Forum: Properties of Electrons
Topic: Lyman, Balmer and Paschen Series
Replies: 2
Views: 30

Re: Lyman, Balmer and Paschen Series

Hi Jessica, The differences between these series are the energy level transitions they are referring to. The Lyman series comes from electrons which are moving from any energy level to the n=1 energy level. The Balmer series comes from electrons moving from any energy level to the n=2 energy level. ...
by Juliet Stephenson 4E
Sun Oct 13, 2019 2:43 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question 28
Replies: 2
Views: 28

Photoelectric Effect Module Question 28

Hi, I was hoping someone could walk me through Problem 28 on the Photoelectric Module. 28. Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. A. What is the kinetic ener...
by Juliet Stephenson 4E
Sat Oct 12, 2019 11:59 pm
Forum: DeBroglie Equation
Topic: Post Module #35
Replies: 3
Views: 53

Re: Post Module #35

I think the reason why you're getting a different answer is that you're using the incorrect units for velocity. On Friday, Lavelle talked about the units for the DeBroglie equation: h is in joule seconds (kg.m 2 .s -2 seconds). In order for everything to cancel out properly, you need your mass to be...
by Juliet Stephenson 4E
Fri Oct 04, 2019 11:01 am
Forum: Molarity, Solutions, Dilutions
Topic: HW Question G13
Replies: 1
Views: 53

Re: HW Question G13

Hi Annie! Here's how I did this problem. First, we need to calculate the molarity of the diluted NH4NO3 solution using M1V1=M2V2. These values are supplied by the problem. (0.2 M NH4NO3)(1 L)=(M2)(4 L) M2=.05 M NH4NO3 From here, we need to calculate how many moles of NH4NO3 would be present in 100 m...
by Juliet Stephenson 4E
Fri Oct 04, 2019 10:40 am
Forum: Balancing Chemical Reactions
Topic: Homework Question H.5 (c)
Replies: 2
Views: 64

Re: Homework Question H.5 (c)

Hi Anokhi, This is what worked for me: We start with NaCl + SO3 + H2O --> Na2SO4 + HCl. Hydrogen and Sodium are unbalanced. Oxygen is already balanced because it has three moles from SO3 and 1 mole from H2O, which corresponds to the 4 moles of Oxygen in Na2SO4. To balance Hydrogen and Sodium, I'll a...
by Juliet Stephenson 4E
Tue Oct 01, 2019 11:56 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: How do I do problem E.3 on page F45 of the textbook?
Replies: 4
Views: 120

Re: How do I do problem E.3 on page F45 of the textbook?

I believe we're supposed to interpret this image literally, as in there are 9 gallium atoms on the left. I multiplied 9 by the provided molar mass of gallium, which has the same significant figures as the molecular mass aka the mass of a single gallium atom in atomic mass units (AMU). Then I divided...
by Juliet Stephenson 4E
Tue Oct 01, 2019 11:32 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solving for Volume G.5 a)
Replies: 8
Views: 207

Re: Solving for Volume G.5 a)

I had to google this before doing the problem, but mmol stands for millimoles, aka 1/1000 of a mole. So in order to keep all the units consistent, I converted the volume given in a) (2.15 mmol Na+) into moles by dividing by 1000 --> .00215 M Na+. Hope that makes sense!
by Juliet Stephenson 4E
Tue Oct 01, 2019 11:15 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solving for Volume G.5 a)
Replies: 8
Views: 207

Re: Solving for Volume G.5 a)

So this problem is asking us to determine the volume of the solution should be transferred into a flask in order to obtain 2.15 mmol of Na+ . Importantly, this is not a dilution problem. Therefore, we won't be using the M1V1=M2V2 equation. The molarity of the solution won't be changing when we trans...

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