## Search found 100 matches

Fri Mar 13, 2020 11:01 am
Forum: Second Order Reactions
Topic: Graphs
Replies: 7
Views: 106

### Re: Graphs

The key to understanding the graphs is to look at the axis labels, especially if the plot is linear. As mentioned above, graphs of [A], ln[A], and 1/[A] vs t correspond to zero order, first order, and second order reactions when the plots are linear
Fri Mar 13, 2020 10:58 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation
Replies: 5
Views: 33

### Re: Arrhenius equation

A is considered the frequency factor or "pre-exponential" factor and includes the number of collisions with correct orientation. The Arrhenious equation is typically used with problems involving activation energy
Fri Mar 13, 2020 10:56 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated Complex vs Transition State
Replies: 5
Views: 78

### Re: Activated Complex vs Transition State

Would it be correct to say that the activated complex is part of the transition state (or vise versa)? Or are they completely separate from each other
Fri Mar 13, 2020 10:51 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Adsorption v. Absorption
Replies: 3
Views: 23

### Re: Adsorption v. Absorption

^To add onto this, adsorption occurs with a heterogeneous catalyst where the catalyst is in a different phase as the reactants (usually solids), causing them to sit on the surface
Fri Mar 13, 2020 10:47 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Methods
Replies: 3
Views: 38

### Re: Methods

We will never need to use steady-state as he never went over examples and pretty much said explicitly we won't need to. Be sure to be familiar with pre-equilibrium though as we did go over examples for it
Sun Mar 08, 2020 3:47 pm
Forum: Zero Order Reactions
Topic: Differential v Integrated rate law
Replies: 3
Views: 41

### Re: Differential v Integrated rate law

The integrated rate law is the differential rate law written as a function of time. In other words, rather than rate being a function of concentration, rate is a function of time. This can be seen with the graphs of zero order, first order, and second order reactions, in which [A], ln[A], and 1/[A] ...
Sun Mar 08, 2020 3:44 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: intergrated rate law
Replies: 9
Views: 113

### Re: intergrated rate law

Both versions are listed on the equation sheet. However, understanding how to derive them (at least understanding why/what is done) is definitely beneficial and it provides a better understanding of graphs given
Sun Mar 08, 2020 3:38 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: derivations
Replies: 9
Views: 145

### Re: derivations

Derivations can also be helpful to know if you need to manipulate formulas on a test only given certain information. I think knowing the relationship between [A], ln[A], and 1/[A] and time (t) is also useful (specifically the graphs and how they relate to slope)
Sun Mar 08, 2020 3:35 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: units
Replies: 11
Views: 130

### Re: units

Usually written as mol.L-1.s-1, which makes sense given that the rate can be represented by d[A]/dt, where [A] is in mol per liter over the time (dt)
Sun Mar 08, 2020 3:31 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: What is 'A'?
Replies: 5
Views: 82

### Re: What is 'A'?

So A will always be given for a reaction?
Fri Feb 28, 2020 10:18 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 40

### Re: Cell Diagrams

I don't believe H2O shows up anywhere in the cell diagram in that form, as only Hg can show up as a liquid. However, if in redox half reactions it is broken up into H+ and OH- ions then those are obviously included in their aqueous forms
Fri Feb 28, 2020 10:15 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Where to find Ecell values
Replies: 15
Views: 146

### Re: Where to find Ecell values

Does anyone know when you would flip the sign in a half relation? I know that if you flip the equation the sign flips, but then do you not do this when calculating E(cell)? like if they give you the E value in the problem and the equation has to be flipped do you flip the sign? The Ecell values giv...
Fri Feb 28, 2020 10:13 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: nerst
Replies: 7
Views: 121

### Re: nerst

Balancing the redox half reactions will give you n for the nernst equation, since you will balance the charges to determine how many electrons to add to both sides. There are no moles in the equation aside from the concentrations (mol.L-1) or in the Gas constant R
Fri Feb 28, 2020 10:08 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 6
Views: 65

### Re: Concentration Cells

Galvanic and Voltaic cells are both sensitive to changes in [R] and [P], so they can be made with the same components at different concentrations. Concentration cells consist of the same species on both sides but differ in concentrations, like the example from lecture with Ag at 1M and 0.1M
Fri Feb 28, 2020 10:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode vs Cathode
Replies: 15
Views: 146

### Re: Anode vs Cathode

Convention is for the anode to be written on the left side and the cathode written on the right side, hence why Enaught(cell)=E(right)-E(left). As mentioned above, you can always check to see what reaction is happening where, since oxidation occurs at the anode and reduction occurs at the cathode
Sun Feb 23, 2020 5:52 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: max potential
Replies: 4
Views: 41

### Re: max potential

The way I thought of it was similar to potential and kinetic energy. When there is no movement/work done, potential energy is at a max and kinetic energy is 0. However, once something happens, potential energy is converted into kinetic energy, therefore being used and not staying at a maximum. Simil...
Sun Feb 23, 2020 5:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Cell Potential
Replies: 2
Views: 28

### Re: Calculating Cell Potential

John Liang 2I wrote:1) identify the half rxns and look up E for each:

Do you think there would be any cases where E is not given and we would have to calculate it given one of the formulas we have?
Sun Feb 23, 2020 5:44 pm
Forum: Balancing Redox Reactions
Topic: Identifying Half Reactions
Replies: 4
Views: 70

### Re: Identifying Half Reactions

A little bit of cheat too is that MnO4- lost its Oxygen, while H2SO3 gained an Oxygen. Therefore, the MnO4- is reduced while the H2SO3 is oxidized. I'm not sure if this is true in every reaction, but it makes sense
Sun Feb 23, 2020 5:40 pm
Forum: Balancing Redox Reactions
Topic: Adding H2O and OH- to Balance
Replies: 5
Views: 57

### Re: Adding H2O and OH- to Balance

If you're using OH- to balance an equation, I'm going to assume the reaction is occurring under basic conditions. First, balance all elements except for hydrogen and oxygen. Then, add H2O to balance the oxygen on the opposing side. Then, balance the hydrogen by using H+, and then the charges by usi...
Sun Feb 23, 2020 5:35 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Le Chatelier’s Principle
Replies: 11
Views: 125

### Re: Le Chatelier’s Principle

We are still dealing with concentrations like Al and Al3+ or Zn and Zn2+. Therefore, the same principles we learned in the equilibrium unit apply here. If there's too much concentration of one of these ions, the equilibrium will shift to satisfy LeChatelier's. This would then affect Q in the Nernst...
Sun Feb 16, 2020 6:46 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Pressure
Replies: 3
Views: 38

### Re: Pressure

So in other words, pressure affects Gibbs Free Energy because it affects the value of Q?
Sun Feb 16, 2020 6:43 pm
Forum: Van't Hoff Equation
Topic: K in Van't Hoff
Replies: 3
Views: 32

### Re: K in Van't Hoff

Earlier in the quarter we talked about how among changes in temperature, pressure, and concentration, temperature is the only one that can affect the K value for a reaction. Depending on if a reaction is endothermic or exothermic (value of delta H), the K value can be permanently increased or decrea...
Sun Feb 16, 2020 6:39 pm
Forum: Van't Hoff Equation
Topic: given values
Replies: 3
Views: 45

### Re: given values

I think it could be reasonable to have to solve for delta H naught or even one of the temperatures depending on the wording of the problem. The main use for the equation though is calculating K at different temperature values given a value for delta H naught, so ideally you would just be focusing on...
Sun Feb 16, 2020 6:34 pm
Forum: Balancing Redox Reactions
Topic: How do you combine half reactions?
Replies: 4
Views: 48

### Re: How do you combine half reactions?

^You could say that. I think combining half reactions is less about cancelling out reactants/products and more about fitting them on both sides of the reaction, but it's the same concept
Sun Feb 16, 2020 11:31 am
Forum: Balancing Redox Reactions
Topic: oxidation vs reduction
Replies: 19
Views: 242

### Re: oxidation vs reduction

In addition, you can tell by looking at the reaction and observing the oxidation numbers of reactants and products. If the oxidation number increases, the reactant was oxidated, and if the oxidation number decreases, the reactant was reduced
Sun Feb 09, 2020 11:17 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Delta in enthalpy and not entropy
Replies: 6
Views: 59

### Re: Delta in enthalpy and not entropy

There can be a delta (or change in) for enthalpy or entropy since both are state functions. The one equation where delta isn't used is the Boltzmann equation, S=k B lnW, since it is calculating the entropy of the system for that many energy states as opposed to the change in entropy due to a change ...
Sun Feb 09, 2020 11:13 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and Pressure
Replies: 3
Views: 31

### Re: Entropy and Pressure

Entropy increases as a system gets bigger, meaning that the opposite is also true (a smaller volume means entropy decreases). When we are talking about pressure and temperature we are usually talking about a closed system with a piston, so if a piston compresses and increases pressure, volume is dec...
Sun Feb 09, 2020 11:10 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: monoatomic, diatomic, linear, non-linear
Replies: 3
Views: 50

### Re: monoatomic, diatomic, linear, non-linear

The shape affects entropy because it affects the molar heat capacity, which is part of the equation for a change in temperature (delta S = C*ln(T2/T1)). Depending on the shape the molar heat capacity can be 3/2*R, 5/2*R, or 7/2*R
Sun Feb 09, 2020 11:07 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boltzmann Equation
Replies: 3
Views: 37

### Re: Boltzmann Equation

As mentioned above, the Boltzmann Equation is helpful when we are given or can calculate degeneracy (W). The Boltzmann equation also just solves for S and not delta S, whereas the other equations solve for delta S or a change in S
Sun Feb 09, 2020 11:00 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy as an extensive property
Replies: 2
Views: 25

### Re: Entropy as an extensive property

Extensive properties like entropy depend on the amount of material present, which is why entropy increases as the size of the system increases. Intensive properties like density do not depend on the amount of material present, which is why something like density remains constant regardless of the si...
Sun Feb 02, 2020 2:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermodynamics Outline
Replies: 5
Views: 54

### Re: Thermodynamics Outline

The monday of week 6 (week of the midterm) Dr. Lavelle said he would be reviewing past midterm questions to review, so that means we have 3 lectures this week to finish the material. I'm fairly certain we will get through the rest of thermodynamics by then
Sun Feb 02, 2020 2:31 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U = Q
Replies: 8
Views: 43

### Re: Delta U = Q

As mentioned above, delta U will be equal to only q when work (w) is equal to zero. This can be seen in a closed system with constant volume, as work is typically done due to compression or expansion (changes in volume).
Sun Feb 02, 2020 2:28 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First law of thermodynamics
Replies: 3
Views: 34

### Re: First law of thermodynamics

The First Law of Thermodynamics says that for a closed system, internal energy (delta U) changes as a function of heat (q) and work (w). This is laid out in the equation delta U = q + w. Note however that this does not fully describe a system, since we also need entropy to know the probability of be...
Sun Feb 02, 2020 2:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System
Replies: 4
Views: 33

### Re: Isolated System

q of the system + q of the surroundings always equals 0. Since an isolated system has no exchanges with surroundings, q of the surroundings is equal to 0, meaning that q of the system must also be 0.
Sun Feb 02, 2020 2:20 pm
Forum: Calculating Work of Expansion
Topic: Reversible and Irreversible
Replies: 5
Views: 55

### Re: Reversible and Irreversible

In other words, the process is reversible since the system is at equilibrium, correct? So irreversible would mean the change is large enough to not maintain equilibrium?
Sun Jan 26, 2020 2:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy as a state function
Replies: 4
Views: 48

### Re: Enthalpy as a state function

If you remember in lecture Dr. Lavelle gave the example of the hikers climbing up a mountain. They both took different paths but still ended up on the same point on the mountain. Distance traveled, or work in this case, would not be a state property since it differed depending on the path taken. Alt...
Sun Jan 26, 2020 1:55 pm
Forum: Phase Changes & Related Calculations
Topic: State Property
Replies: 6
Views: 51

### Re: State Property

Dr. Lavelle gave an example in class with the heating curve for water. The graph showed heat absorbed on the x-axis and temperature on the y-axis. As heat constantly increased, the temperature remained constant and only increased once certain thresholds were reached (melting or boiling points). The ...
Sun Jan 26, 2020 1:50 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes: endothermic vs exothermic
Replies: 12
Views: 171

### Re: Phase changes: endothermic vs exothermic

The energy change in the reverse reaction will always be the opposite of the forward reaction since the heat curve is flipped. So the reverse reaction for something endothermic such as vaporization would be exothermic
Sun Jan 26, 2020 1:48 pm
Forum: Phase Changes & Related Calculations
Topic: Work
Replies: 3
Views: 61

### Re: Work

Something also of note is that work is not a state property, meaning that it depends the "path" taken to obtain it. It cannot be added or subtracted like other properties such as enthalpy or pressure.
Sun Jan 26, 2020 1:45 pm
Forum: Phase Changes & Related Calculations
Topic: steam vs liquid burn
Replies: 2
Views: 21

### Re: steam vs liquid burn

The process of water becoming a gas (vaporization) takes much longer than the process of ice becoming water (melting). Since this process is longer, more heat is supplied throughout and the enthalpy is greater, meaning that the steam will release much more energy/heat as opposed to the liquid
Sun Jan 19, 2020 3:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 10
Views: 112

### Re: 5% rule

The 5% rule can be applied after making an approximation for x. You calculate x/[initial concentration given] and if the value is less than 5% (0.05) then the approximation is valid. However, if the value is greater than 5% then you must reject the approximation and recalculate x
Sun Jan 19, 2020 3:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations
Replies: 12
Views: 88

### Re: Concentrations

Changing the concentration or pressure can cause the equilibrium to "favor" the products or reactants, but in both cases the equilibrium constant K will stay the same. Only when temperature is changed is K changed because of a permanent change in the system's dynamics (depending on if it's...
Sun Jan 19, 2020 3:25 pm
Forum: Ideal Gases
Topic: Ideal Gas meaning
Replies: 7
Views: 114

### Re: Ideal Gas meaning

If we are required to convert between pressure and concentration or vice versa, you should be safe using the Ideal Gas Law. Ideal gases were not heavily discussed in class so it should be fairly safe to use the equation when necessary to convert
Sun Jan 19, 2020 3:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: lewis structure
Replies: 11
Views: 87

### Re: lewis structure

As mentioned above he usually draws them so that we can better visualize what is happening during the reaction. I would be surprised if we had to draw one for the test, but I could see one being given for us to use as part of a question.
Sun Jan 19, 2020 3:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Solids and Liquids
Replies: 6
Views: 57

### Re: Solids and Liquids

Most solids and liquids are pure substances, meaning their molar concentration does not change in the reaction. Therefore, it will not affect the equilibrium concentrations of other reactants/products
Sun Jan 12, 2020 12:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs Kp
Replies: 10
Views: 73

### Re: Kc vs Kp

^So are they the same in the case of ideal gases then? Or whenever P=n/V is true?
Sun Jan 12, 2020 12:22 pm
Forum: Ideal Gases
Topic: Topics on Test 1
Replies: 37
Views: 424

### Re: Topics on Test 1

The tests will be given starting Tuesday of week 3, so I imagine whatever we cover in these first two weeks will be on there. I would pay attention to how far he gets in lecture and whatever your TA reviews in discussion
Sun Jan 12, 2020 12:16 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 19
Views: 245

### Re: Le Chatelier's Principle

Is it appropriate to consider Le Chatelier's Principle as a ratio? I.e. determining the change of one value would aid in determining the other values and thus, the equilibrium? I believe so. Since the equilibrium constant K does not change regardless of changes in concentration or pressure, the cha...
Sun Jan 12, 2020 12:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q<K
Replies: 4
Views: 25

### Re: Q<K

The reaction quotient Q is similar to K since they both involve products over reactants ([P]/[R]), with the difference being that Q is taken at any point in the reaction while K is that ratio taken at equilibrium. Therefore, if you observe that Q<K, you know that there is a greater concentration of ...
Sun Jan 12, 2020 12:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: when to use Kc vs Kp
Replies: 11
Views: 77

### Re: when to use Kc vs Kp

As others mentioned, brackets denote concentration (in mol.L-1), so you wouldn't use them when calculating partial pressure for Kp. However, just because you are given all gases does not necessarily mean you will be calculating Kp, so pay attention to what the question asks and what values are given
Sat Dec 07, 2019 11:05 pm
Forum: Naming
Topic: naming ligands in alphabetical order
Replies: 2
Views: 39

### Re: naming ligands in alphabetical order

When writing the compound itself I don't believe order matters, so long as everything inside the brackets in inside and everything that should be outside is outside. Typically the transition metal cation is written first in the formula, but I'm not sure if that is absolutely required or just a forma...
Sat Dec 07, 2019 11:01 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic
Replies: 7
Views: 155

### Re: Amphiprotic

Amphiprotic means that the molecule can both receive and donate protons. Amphoteric means that the molecule can act as both an acid and a base. All amphoteric molecules are amphiprotic, but not all amphiprotic molecules are amphotertic
Sat Dec 07, 2019 11:00 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxoacid Strength
Replies: 6
Views: 214

### Re: Oxoacid Strength

^Correct. Strength for oxoacids is based on the stability of the resulting anion, which is influenced by electronegativity (withdraws electron density) and resonance. Typically I would just look at which acid contains the more electronegative atom
Sat Dec 07, 2019 10:56 pm
Forum: Calculating the pH of Salt Solutions
Topic: Titrations
Replies: 6
Views: 160

### Re: Titrations

The specifics of titration are more important for 14B and 14BL. For the final I would understand the stoichiometric point and its significance
Sat Dec 07, 2019 10:55 pm
Forum: General Science Questions
Topic: Curve
Replies: 9
Views: 341

### Re: Curve

From my understanding, the scores themselves are not curved. However, based on the total grades at the end of the quarter, course grades will be adjusted accordingly.
Sun Dec 01, 2019 1:11 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds - do we need to memorize them?
Replies: 2
Views: 49

### Re: Amphoteric Compounds - do we need to memorize them?

I would be familiar with those elements involved, but I don't know if you need to fully memorize them. To determine if an element is amphoteric, you can look chemical reactions involving them to see if they are capable of acting as both an acid and a base (able to donate or accept a proton when nece...
Sun Dec 01, 2019 1:09 pm
Forum: Amphoteric Compounds
Topic: determining if compounds are acids, bases, or amphoteric
Replies: 3
Views: 49

### Re: determining if compounds are acids, bases, or amphoteric

Looking at chemical reactions involving the compound and seeing what the resulting products are will probably be the most useful. I would think that a reaction would be given or they would tell you if it is acidic, basic, or amphoteric to begin with. I would also just be familiar with typical acidic...
Sun Dec 01, 2019 12:52 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Reactions, Equilibrium
Replies: 4
Views: 56

### Re: Reactions, Equilibrium

Is there notation to show the direction a reaction is favoring, or do you still just write the double pointing arrow?
Sun Dec 01, 2019 12:48 pm
Forum: Naming
Topic: Ligands
Replies: 6
Views: 96

### Re: Ligands

^I agree. Memorizing isn't always the best method, but I think in this case you just need to know the values as it will definitely save you some time
Sun Dec 01, 2019 12:43 pm
Forum: Naming
Topic: How to Find the Roman Numeral
Replies: 4
Views: 81

### Re: How to Find the Roman Numeral

Typically you want to find it by process of elimination. See what the overall charge of the coordination compound is, and then determine what components inside are that make it up. From there, the roman numeral will take on whatever value it needs to be so that the components equal the total charge....
Sun Nov 24, 2019 12:35 pm
Forum: Biological Examples
Topic: myoglobin and hemoglobin
Replies: 3
Views: 60

### Re: myoglobin and hemoglobin

Knowing the biological function of both is important to understanding their purpose, but since this is a chem class I think knowing their structures and the roles of coordination compounds is more significant
Sun Nov 24, 2019 12:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 23
Views: 210

### Re: Seesaw

I have in my notes that they are equal to 90 and 120, but I think using the lone pair as reasoning you wouldn't be marked wrong for writing less than 90 and less than 120
Sun Nov 24, 2019 12:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Specific Naming Question
Replies: 4
Views: 74

### Re: Specific Naming Question

I think we only have to worry about molecular geometry for this class, just be aware of how many regions of electron density there are in general
Sun Nov 24, 2019 12:26 pm
Forum: Hybridization
Topic: Hybridization Confusion
Replies: 3
Views: 54

### Re: Hybridization Confusion

I would also be familiar with what molecular shapes correspond to what hybridized orbitals. For example, shapes such as Tetrahedral or Trigonal Pyramidal have 4 regions of electron density, therefore having the sp^2 hybridized orbitals
Sun Nov 24, 2019 12:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: homework
Replies: 3
Views: 52

### Re: homework

I would double check with your TA but doing hybridization and sigma/pi bonds problems should be fine since they were recently covered. There also aren't many problems for coordination compounds so I would think it's okay
Sun Nov 17, 2019 1:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Wed before Thanksgiving
Replies: 3
Views: 60

### Re: Wed before Thanksgiving

Classes are only cancelled on Thursday and Friday, so unless Lavelle himself gives us the day off, we should have lecture as usual
Sun Nov 17, 2019 1:09 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: Size and Electronegativity difference
Replies: 3
Views: 68

### Re: Size and Electronegativity difference

From what I've been told you will usually be able to tell which one to compare. The molecules given will usually be similar in either electronegativity or size, so use that as a baseline and look at the one that's different
Sun Nov 17, 2019 1:03 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 Points
Replies: 9
Views: 129

### Re: Boiling Points

Is this the same for melting points? So stronger IMF's also lead to higher melting points?
Sun Nov 17, 2019 12:57 pm
Forum: Bond Lengths & Energies
Topic: Quiz for Next week dashes/wedges
Replies: 11
Views: 138

### Re: Quiz for Next week dashes/wedges

In class he mentioned that we can just draw a normal Lewis Structure as long as we name the shape I think. Do we have to worry about where we arrange the atoms around the central atom (example: drawing a tetrahedral shape vs square planar) or can we just draw it normally and name the shape after?
Sun Nov 10, 2019 3:23 pm
Forum: Sigma & Pi Bonds
Topic: hybridization
Replies: 2
Views: 48

### Re: hybridization

Will we go into more detail in lecture about this concept? I also remember it being mentioned but I don't have much written down either.
Sun Nov 10, 2019 3:20 pm
Forum: Octet Exceptions
Topic: Octet Exception
Replies: 8
Views: 223

### Re: Octet Exception

From my understanding, you really only have to worry about the octet rule with 2nd period elements (mainly N, O, F). As others mentioned, once you reach 3rd period elements, d-orbitals can accommodate extra electrons.
Sun Nov 10, 2019 3:16 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Showing Work
Replies: 6
Views: 95

### Re: Showing Work

Partial points can never hurt, I would only not write it out if I'm in a crunch for time
Sun Nov 10, 2019 3:15 pm
Forum: Dipole Moments
Topic: HW this week
Replies: 6
Views: 59

### Re: HW this week

Since we don't have lecture tomorrow, I would assume it's fine to do homework on last section's problems. We haven't covered enough of the new section to do many of the newer problems.
Sun Nov 10, 2019 3:13 pm
Forum: Bond Lengths & Energies
Topic: test 2
Replies: 16
Views: 160

### Re: test 2

Test 2 is in week 8, right? I'm sure some of the prior material will be on it (at least the stuff on chemical bonds) since otherwise it'll only be covering a week or so of material.
Sun Nov 03, 2019 4:52 pm
Forum: Bond Lengths & Energies
Topic: Midterm Question
Replies: 5
Views: 84

### Re: Midterm Question

If I remember correctly Dr. Lavelle said that the final slide he went over in lecture on Friday (the one describing interactions that give rise to attractive forces) would not be on the midterm. However, everything else up to that point would be fair game. I don't think you need to know specific val...
Sun Nov 03, 2019 4:47 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Shortcut
Replies: 4
Views: 65

### Re: Formal Charge Shortcut

I'm not sure if this is the same as what you're describing, but the shortcut I was given was just to count the electrons around the drawn atom and see if they match the number of valence electrons that atom should have. You erase the middle of any bonds, showing that each atom is giving one electron...
Sun Nov 03, 2019 4:42 pm
Forum: Ionic & Covalent Bonds
Topic: Drawing Ionic Compunds
Replies: 7
Views: 183

### Re: Drawing Ionic Compunds

So the brackets are drawn as opposed to the atoms being bonded since they're ions, correct? So we'd be marked wrong for including a bond between them?
Sun Nov 03, 2019 4:32 pm
Forum: Sigma & Pi Bonds
Topic: Significance of sigma and pi bonds
Replies: 4
Views: 62

### Re: Significance of sigma and pi bonds

Are sigma and pi bonds shown in Lewis Structures or only in describing bond character?
Sun Nov 03, 2019 4:29 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bonds
Replies: 3
Views: 50

### Re: Sigma and Pi Bonds

Can sigma and pi bonds be found in single or triple bonds too or only double bonds?
Sun Oct 27, 2019 12:57 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 7
Views: 110

### Re: Formal Charge

Anna Chen 4L wrote:The resonance structure with the lowest formal change is the most stable.

I thought the structure with its formal charge = 0 or closest to 0 was the most stable?
Sun Oct 27, 2019 12:51 pm
Forum: Lewis Structures
Topic: Expanded Octet
Replies: 6
Views: 66

### Re: Expanded Octet

In class I remember Phosphorus, Sulfur, and Chlorine being given as examples. Are other elements beyond these 3 capable of having an expanded octet. I have written in my notes that atoms in Period 3 or higher have d-orbitals in valence shells that accommodate additional electrons, so does that apply...
Sun Oct 27, 2019 12:45 pm
Forum: Lewis Structures
Topic: Drawing the structure
Replies: 7
Views: 84

### Re: Drawing the structure

It's still a Lewis Structure, just seems different because Phosphorus is capable of having an expanded octet
Fri Oct 25, 2019 10:29 am
Forum: Trends in The Periodic Table
Topic: Calculated vs Observed Value
Replies: 6
Views: 72

### Re: Calculated vs Observed Value

I know we haven't covered it yet, but will we eventually need to know how to calculate electronegativity for a specific element? Or will we just need to know the trend for the table
Fri Oct 25, 2019 10:24 am
Forum: Trends in The Periodic Table
Topic: week 4 Hw problems
Replies: 4
Views: 70

### Re: week 4 Hw problems

Technically we've moved on to the Chemical Bonds section but I imagine it's fine, similar to how he allowed us to turn in homework from the first section because we had a test coming up. You can always email your TA just to be sure.
Sun Oct 20, 2019 6:13 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Configuration of 3d and 4s orbitals
Replies: 1
Views: 22

### Re: Configuration of 3d and 4s orbitals

I think Dr. Lavelle explained in class that 4s is written after 3d since 3d has lower energy than 4s. Typically the orbitals are listed in ascending order of energy
Sun Oct 20, 2019 6:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D.23
Replies: 1
Views: 34

### Re: 1D.23

Basically the question is asking how many possible values of m l there are for the given set of quantum numbers. Remember, the value of m l ranges from l to -l. For b) and d), the answer is 1 since they give you m l already. For a), the answer is 3 since m l can be 1, 0, or -1 given l=1. For c), the...
Sun Oct 20, 2019 5:48 pm
Forum: Properties of Light
Topic: Modules
Replies: 5
Views: 87

### Re: Modules

On the Learning Outcomes outline for Chemical Bonds (the next topic) there is no mention of watching modules for that section. He could update it later, but those are likely set in stone as outlines for the rest of the quarter. As mentioned above, the modules were likely just to help ease people bac...
Fri Oct 18, 2019 10:23 am
Forum: Einstein Equation
Topic: Mass of a proton and neutron
Replies: 3
Views: 51

### Re: Mass of a proton and neutron

The mass of protons, neutron, and electrons will always be given on a formula/constants sheet. There's a link on the class website called "Constants and Equations" that you can use for homework
Fri Oct 18, 2019 10:20 am
Forum: DeBroglie Equation
Topic: the m in the de broglie equation
Replies: 5
Views: 64

### Re: the m in the de broglie equation

m could represent the mass of an object, like a baseball or car as others mentioned, or a particle such as a proton, neutron, or electron. The only thing it can't represent is a photon since photons have no mass. If the problem involves a photon/light, use c=wavelength*frequency.
Sun Oct 13, 2019 4:14 pm
Forum: Properties of Light
Topic: SI units and wavelength
Replies: 6
Views: 47

### Re: SI units and wavelength

As others mentioned you'll almost always see wavelength measured in meters (m) since it's distance. However, it's usually an extremely small number, so I'd recommend knowing the different prefixes (nano, pico, etc) in case it's given like that.
Sun Oct 13, 2019 4:06 pm
Forum: Photoelectric Effect
Topic: Video Modules
Replies: 7
Views: 68

### Re: Video Modules

The modules were very beneficial for me when it came to studying for the first test on High School topics. If you don't have time to watch them before the lectures, I would at least recommend taking the pre/post module test when reviewing as another way to practice.
Fri Oct 11, 2019 10:37 am
Forum: Student Social/Study Group
Topic: Study Tips
Replies: 58
Views: 2147

### Re: Study Tips

Aside from the lectures, what's helped me understand the material most has been the video modules posted and doing extra homework problems. When I do the problems, however, I try not to use my notes or the textbook as help to see if I've really grasped what I need to do. Reviewing notes is definitel...
Fri Oct 11, 2019 10:34 am
Forum: Student Social/Study Group
Topic: Turning in Extra HW problems
Replies: 10
Views: 212

### Re: Turning in Extra HW problems

Nothing has been mentioned about extra credit, so I doubt turning in extra HW would directly help your grade. However, as others mentioned, it's definitely still helpful to do more than the required 5, especially when studying for tests since a lot of the problems are similar to the ones assigned.
Fri Oct 11, 2019 10:31 am
Forum: Student Social/Study Group
Topic: Pen or Pencil for Homework Problems?
Replies: 8
Views: 136

### Re: Pen or Pencil for Homework Problems?

I typically use pencil for homework since I tend to erase a lot and it helps me be neater without having to cross things out. If you want to work in pen you can always work out a problem on scratch paper and then transfer it onto the homework so it's neater/more detailed. Up to you, I think it's fai...
Fri Oct 04, 2019 10:40 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Rounding
Replies: 12
Views: 345

### Re: Rounding

I generally round out to 2 or 3 decimal places, depending on the numbers given in the problem like those above me mentioned. You should be fine as long as you aren't rounding egregiously (Ex: rounding 16.53 to 17 for atomic weight). It also depends on context though. I typically wouldn't round like ...
Fri Oct 04, 2019 10:28 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Aqueous, solid, gas
Replies: 11
Views: 206

### Re: Aqueous, solid, gas

From my understanding, aqueous refers to an element/molecule dissolved in a solvent, typically water. The molecule is a solid, but it is dissolved in the solvent so it's referred to as aqueous. Liquid, on the other hand, is a "pure" form of the substance, meaning that it isn't dissolved in...
Fri Oct 04, 2019 10:21 am
Forum: Molarity, Solutions, Dilutions
Topic: Converting Before or After?
Replies: 10
Views: 157

### Re: Converting Before or After?

^To add on to this, I would definitely convert after since it could make your calculations a little wonky if you converting during. Only convert during the calculations if you need units to cancel out (they usually should regardless), so I would suggest waiting until the end.
Fri Oct 04, 2019 10:15 am
Forum: Empirical & Molecular Formulas
Topic: Test Materials
Replies: 13
Views: 227

### Re: Test Materials

Since we have to use a pen for the exam, are we allowed to use pencil and/or a piece of scratch paper to work things out? I feel like I would have to cross a lot of things out working in pen.
Fri Oct 04, 2019 10:11 am
Forum: Limiting Reactant Calculations
Topic: Fundamentals M15
Replies: 3
Views: 60

### Re: Fundamentals M15

^Thank you for this explanation, I found it very helpful. Will there be problems like this in the future where the molecules in the reaction are given by name as opposed to as the equation? (Ex: if they had given us Al(s) + Cl2(g) ---> AlCl3(s))

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