## Search found 105 matches

Wed Mar 18, 2020 12:21 am
Forum: Administrative Questions and Class Announcements
Topic: Athena
Replies: 34
Views: 1975

### Re: Athena

Thank you for this, you definitely make the world a better place! I hope you can finally get some rest now that the online final is over!
Wed Mar 18, 2020 12:20 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 282
Views: 134698

### Re: Saying Thank You to Dr. Lavelle

Dear Dr. Lavelle, Thank you for all of your amazing efforts the past two quarters! The amount of time you put into creating recourses for your students is greatly appreciated, especially considering the change that has recently taken place. Your immense consideration for your students’ success and y...
Wed Mar 18, 2020 12:16 am
Forum: Ideal Gases
Topic: R Constant
Replies: 26
Views: 326

### Re: R Constant

I always just look at the units given, and it’s usually pretty easy to tell. Sometimes, temperature might need to be changed to Kelvin though!
Wed Mar 18, 2020 12:15 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G of ionization
Replies: 3
Views: 308

### Re: Delta G of ionization

Yes it is, it’s just a way to make it clear what the change in gibbs free energy is due to.
Wed Mar 18, 2020 12:13 am
Forum: Ideal Gases
Topic: Kc
Replies: 7
Views: 97

### Re: Kc

Also, if there is a liquid or solid in either the products or the reactants, they would just be included in Kc as 1, so obviously they can be disregarded. I like to include this just for clarity.
Sun Mar 08, 2020 5:48 pm
Forum: General Rate Laws
Topic: integrated rate laws
Replies: 7
Views: 75

### Re: integrated rate laws

The rate law shows the rate of the reaction plotted against time while the integrated rate law shows the actual concentration at certain times. If you think about it in terms of calculus and the definition of an integral, this makes sense.
Sun Mar 08, 2020 5:44 pm
Forum: General Rate Laws
Topic: derivations?
Replies: 5
Views: 53

### Re: derivations?

I think its more helpful to know the derivation for comprehension purposes, but it is pretty unlikely he will ask us to derive one of these equations on the test.
Sun Mar 08, 2020 5:43 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: derivations
Replies: 9
Views: 145

### Re: derivations

I believe that knowing the derivation of the rate laws and even the half lives is important to develop a proper understanding, however, Dr. Lavelle did not go over the derivation of the Arrhenius equation in class.
Sun Mar 08, 2020 5:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 7
Views: 49

### Re: Cell Diagrams

Either inert metal can be used when either the cathode or the anode has no solid conductor, but platinum is the most common.
Sun Mar 08, 2020 5:36 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetically stable?
Replies: 10
Views: 128

### Re: kinetically stable?

This means the the activation energy, the hump in the reaction profile, is very high.
Sun Mar 01, 2020 8:36 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: cell diagrams
Replies: 8
Views: 81

### Re: cell diagrams

I believe that most of the time, the cell will have this layout, but there are instances where it can be the other way around, so it’s important to pay attention to what is being oxidized and what is being reduced in each individual case instead of assuming.
Sun Mar 01, 2020 8:33 pm
Forum: Balancing Redox Reactions
Topic: Redox Reactions and Acid/Base Reactions
Replies: 9
Views: 109

### Re: Redox Reactions and Acid/Base Reactions

Like the other students said, redox reactions are not always acid or base reactions, I just think the examples used are often acid or base because it is more complicated to balance the half reactions, which allows us to practice more!
Sun Mar 01, 2020 8:32 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: delta G=-nFE
Replies: 7
Views: 117

### Re: delta G=-nFE

If n is not given, you can go through the process of balancing the half reactions for oxidation and reduction, eventually finding the number of moles of electrons being transferred!
Sun Mar 01, 2020 8:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: electrodes
Replies: 5
Views: 50

### Re: electrodes

In practice, I have only ever seen platinum being used as the inert metal in the electrolytic cell, so I just like to play it safe and use that!
Sun Mar 01, 2020 8:29 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: when to use K or Q
Replies: 18
Views: 234

### Re: when to use K or Q

K is used when the reaction is specified as being at equilibrium while Q is used when the reaction is not at equilibrium.
Sat Feb 22, 2020 9:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Finding n
Replies: 6
Views: 68

### Re: Finding n

Considering the constant F in electrochemistry, it can be concluded that n refers to the number of moles of electrons being transferred and this is easy to remember since redox reactions come down to an exchange of electrons reducing or oxidizing an atom or molecule.
Sat Feb 22, 2020 9:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: property of E
Replies: 6
Views: 45

### Re: property of E

It simply comes down to E being an intensive property, meaning that the difference in voltage will not change if the reaction takes place more than once whereas gibbs free energy, for instance, will change.
Sat Feb 22, 2020 9:35 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ecell
Replies: 5
Views: 341

### Re: Ecell

Two are given since one refers to standard conditions, 25 degrees C and 1 atm while the other can refer to any condition separate from standard.
Sat Feb 22, 2020 9:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 10
Views: 116

### Re: Salt Bridge

In order to counteract the build up of charge in a galvanic cell, the salt bridge essentially contributes free ions that will not interfere with the redox reaction that is already taking place, it is simply meant to neutralize each side.
Sat Feb 22, 2020 9:31 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nerst Equation
Replies: 10
Views: 471

### Re: Nerst Equation

I think it’s always helpful to know how to derive the equation because once you are able to do that, you know you have a proper grasp of the concepts. However, we are not expected to do this on an exam!
Sun Feb 16, 2020 12:39 pm
Forum: Calculating Work of Expansion
Topic: work = 0
Replies: 14
Views: 240

### Re: work = 0

In a vacuum, the external pressure is equal to 0, so during free expansion, work is also equal to 0.
Sun Feb 16, 2020 12:38 pm
Forum: General Science Questions
Topic: 50 post grade
Replies: 25
Views: 807

### Re: 50 post grade

My TA last quarter checked at the very end to make sure we made 50 posts, but that could vary depending on your TA.
Sun Feb 16, 2020 12:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 509

### Re: Midterm Curve

Sadly, no curve for individual tests since there is a curve at the end of the quarter depending on how students do overall. To pass the class, you only need 50% of points.
Sun Feb 16, 2020 12:33 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Delta E
Replies: 11
Views: 198

### Re: Delta E

These are interchangeable!
Sun Feb 16, 2020 12:32 pm
Forum: Ideal Gases
Topic: pv=nrt
Replies: 19
Views: 244

### Re: pv=nrt

Yes you can, make sure the R value is the correct one though!
Sat Feb 08, 2020 8:49 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Difference between Molar Entropy and Standard Residual Entropy
Replies: 3
Views: 311

### Re: Difference between Molar Entropy and Standard Residual Entropy

Yes, W would be the correct notation.
Sat Feb 08, 2020 8:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Measuring ∆G°
Replies: 2
Views: 33

### Re: Measuring ∆G°

Yes, I agree! I remember it being mentioned in lecture that it would be meaningless to try to actually measure free energy alone, so the equation must be used in order to find the value of the standard change in Gibbs free energy.
Sat Feb 08, 2020 8:46 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: degeneracy
Replies: 7
Views: 52

### Re: degeneracy

Degeneracy relates to thermodynamics in that it is used to calculate the change in entropy. The way I remember it is that Lavelle mentioned that he was purposefully avoiding the word disorder in regards to the topic of entropy because degeneracy is a better way to describe what entropy is and what i...
Sat Feb 08, 2020 8:40 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: degeneracy relation to thermo
Replies: 5
Views: 70

### Re: degeneracy relation to thermo

I agree! I see more of a connection to quantum mechanics as well, but the way I see it in terms of thermodynamics is when considering entropy. Rather than using words such as "disorder" when describing entropy, degeneracy is a more thorough explanation.
Sat Feb 08, 2020 8:37 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 5
Views: 56

### Re: Calorimeter

A calorimeter is also a perfect example of an isolated system, and the heat capacity of the calorimeter must be taken into account along with the heat capacity of the solution inside of the calorimeter.
Sat Feb 01, 2020 9:10 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible vs irreversible expansion
Replies: 4
Views: 44

### Re: reversible vs irreversible expansion

For reversible expansion, the external pressure can change, which is proven by the integral used to calculate q. For irreversible expansion, external pressure remains constant, which is the reason that the calculation of q is much more simple.
Sat Feb 01, 2020 9:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Systems
Replies: 8
Views: 92

### Re: Closed Systems

Insulation is the main difference between the two systems. For an isolated system, a calorimeter is a great example because it is insulated, ensuring that heat will not be exchanged between the system and the surroundings.
Sat Feb 01, 2020 9:06 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated system
Replies: 13
Views: 105

### Re: isolated system

In AP chemistry, we did an experiment where we made our own calorimeter using double foam cups to make sure that neither matter nor energy can be exchanged between the system and the surroundings.
Sat Feb 01, 2020 9:05 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 198

### Re: Closed vs isolated systems

A closed system has the ability to exchange energy with the surroundings, but not matter, while an isolated system cannot exchange either, such as a calorimeter.
Sat Feb 01, 2020 9:03 pm
Forum: Calculating Work of Expansion
Topic: integral
Replies: 3
Views: 43

### Re: integral

The purpose of the integral is to account for the infinitesimally small steps in reversible expansion, so you would use it in that context. If you were confused at all in lecture, the textbook explains it pretty well also.
Fri Jan 24, 2020 10:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculation methods
Replies: 6
Views: 50

### Re: Calculation methods

I remember method 4 being used a lot in AP Chem, so that might mean that it will be coming up pretty often.
Fri Jan 24, 2020 10:20 pm
Forum: Phase Changes & Related Calculations
Topic: Bond enthalpy
Replies: 4
Views: 35

### Re: Bond enthalpy

I agree! This association makes sense, but I am not completely sure.
Fri Jan 24, 2020 10:17 pm
Forum: Ideal Gases
Topic: ICE table approximation
Replies: 10
Views: 78

### Re: ICE table approximation

To verify that the approximation is valid, divide x by the initial value and multiply by 100, and if the value is less than 5%, then it is valid.
Fri Jan 24, 2020 10:15 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 43
Views: 513

### Re: Kc vs Kp

It all depends on the information given. You would use Kp when the partial pressures are given, but you use Kc when the concentration or moles or grams are given even when the reactants and products are gases.
Fri Jan 24, 2020 10:13 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic values
Replies: 5
Views: 41

### Re: Endothermic values

I find it helpful to add the plus sign just to reinforce the fact that there is a positive change in enthalpy, but I do not think it is absolutely necessary.
Fri Jan 17, 2020 8:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5 percent rule
Replies: 10
Views: 94

### Re: 5 percent rule

The 5% rule is used to verify that assuming x to be negligibly small is a correct assertion. It is simply the calculation of percent protonation.
Fri Jan 17, 2020 8:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Equilibrium
Replies: 9
Views: 95

### Re: Solids and Equilibrium

Since both solids and liquids are pure substances, they do not change either.
Fri Jan 17, 2020 8:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE
Replies: 5
Views: 76

### Re: ICE

To determine if an ICE table is necessary, look at the information given. Such as, if the initial concentration(s) are given along with a Ka or Kb value, then an ICE table is the correct method in finding the equilibrium concentrations and other information.
Fri Jan 17, 2020 8:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables
Replies: 5
Views: 66

### Re: ICE tables

To determine if an ICE table is necessary, look at the information given, such as the initial concentration of a weak acid or base and the ka or kb value rather than the equilibrium concentration.
Fri Jan 17, 2020 8:26 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for weak acids
Replies: 5
Views: 235

### Re: pH for weak acids

Since pH is determines by the concentration of H3O+ ions in the solution, the greater protonation yields a lower pH, and strong acids are known to be 100% dissociated, meaning a higher concentration of H3O+.
Fri Jan 17, 2020 8:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Tips for Test
Replies: 23
Views: 266

### Re: Tips for Test

I often study by doing several if not all of the problems outlined in the syllabus and reading the given chapters in the textbook. Also, if time permits, the peer learning sessions could be extremely helpful.
Fri Jan 10, 2020 10:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: predicting effects
Replies: 9
Views: 149

### Re: predicting effects

Removing some product would in turn lead to the reaction proceeding to the right and more products being formed.
Fri Jan 10, 2020 10:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 10
Views: 84

### Re: Units for K

The combination of K being a measurement of activity as well as the fact that it is a constant, means that it does not have ay units.
Fri Jan 10, 2020 10:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating the Equilibrium Quotient
Replies: 3
Views: 72

### Re: Calculating the Equilibrium Quotient

The reaction quotient is basically the ratio of concentration of products to the concentration of reactants at any point in a reaction, which is used to compare to the equilibrium constant, K, the same ratio but only at equilibrium, in order to determine the future behavior of the reaction(whether i...
Fri Jan 10, 2020 10:27 pm
Forum: Ideal Gases
Topic: K value
Replies: 14
Views: 149

### Re: K value

A large K value indicates that the products of the reaction are more favorable and the reaction lies to the right, whereas a small K value indicates that the reactants are more favorable and the reaction lies to the left at equilibrium.
Fri Jan 10, 2020 10:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Small "x" approximations for cubic equations
Replies: 3
Views: 37

### Re: Small "x" approximations for cubic equations

I remember learning this before too! I believe it was 10^-3 as well! I remember always proving that x was negligibly small in order to make it clear why that simplification is possible as well.
Sat Dec 07, 2019 9:20 pm
Forum: Student Social/Study Group
Topic: Grades
Replies: 14
Views: 406

### Re: Grades

From my understanding, I believe he curves the class at the end based on the class average, but I am not too sure how.
Sat Dec 07, 2019 9:14 pm
Forum: Naming
Topic: Memorization
Replies: 4
Views: 160

### Re: Memorization

I like to think of it this way as well, and when you practice naming coordination compounds, it becomes more and more familiar.
Sat Dec 07, 2019 9:12 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs amphiprotic
Replies: 4
Views: 121

### Re: Amphoteric vs amphiprotic

Basically, a compound that can give or receive protons, amphiprotic, can act as either an acid or a base, amphoteric.
Sun Dec 01, 2019 7:06 pm
Forum: Lewis Acids & Bases
Topic: Bases
Replies: 4
Views: 45

### Re: Bases

I like to think of this in terms of the equations used to find pH which is in terms of the logarithm of the concentration of H+ or OH-, which makes sense conceptually for this question.
Sun Dec 01, 2019 7:04 pm
Forum: Lewis Acids & Bases
Topic: Strong Acids/Bases
Replies: 2
Views: 31

### Re: Strong Acids/Bases

Also, in addition to this, enzymes usually perform under a vital pH, and when the environment is functions in is not this pH, the enzyme may become denatured, which changes its active site.
Sun Dec 01, 2019 7:02 pm
Forum: Lewis Acids & Bases
Topic: Lewis Acids
Replies: 3
Views: 54

### Re: Lewis Acids

I like using both definitions simultaneously because they complement each other well and can be depicted in an actual acid-base reaction.
Sun Dec 01, 2019 6:59 pm
Forum: Lewis Acids & Bases
Topic: Donating Proton vs Accepting Electron
Replies: 4
Views: 73

### Re: Donating Proton vs Accepting Electron

This is a great example of how the interaction works and how the definitions of lewis and bronsted acids/bases can be applied to a real scenario.
Sun Dec 01, 2019 6:55 pm
Forum: Lewis Acids & Bases
Topic: Difference between Lewis and Bronsted Acids?
Replies: 2
Views: 42

### Re: Difference between Lewis and Bronsted Acids?

Basically, they are viewed differently in respect to the protons and electrons being gained or lost. A Bronsted acid is a proton donor while a lewis acid is an electron acceptor and the bases of each reflect the same pattern but are relatively opposite.
Sun Nov 24, 2019 6:09 pm
Forum: Dipole Moments
Topic: Melting points
Replies: 15
Views: 393

### Re: Melting points

When determining relative melting points, consider the strength of the IMFs involved.
Sun Nov 24, 2019 6:08 pm
Forum: Hybridization
Topic: Lone pairs
Replies: 9
Views: 115

### Re: Lone pairs

I like to think of it as since lone pairs affect shape, they also affect hybridization, since they are electrons too, just not shared electrons!
Sun Nov 24, 2019 6:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs linear
Replies: 56
Views: 1139

### Re: Bent vs linear

A bent molecule will have one or two lone pairs with VESPR functions AX2E and AX2E2
Sun Nov 24, 2019 6:03 pm
Forum: Lewis Acids & Bases
Topic: Lewis and Bronsted
Replies: 5
Views: 66

### Re: Lewis and Bronsted

A Bronsted acid is a proton donor while a Lewis acid is a proton acceptor.
Sun Nov 24, 2019 6:01 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 15
Views: 312

### Re: Electronegativity

A higher electronegativity difference indicates a stronger bond, which can be exemplified with hydrogen bonds when considering that hydrogen has a very small electronegativity.
Sun Nov 24, 2019 5:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 23
Views: 210

### Re: Seesaw

A lone pair should always change the angle at least slightly, so the actual angles would be less than 90 and 120.
Sun Nov 24, 2019 5:58 pm
Forum: Lewis Acids & Bases
Topic: lewis vs. bronsted
Replies: 10
Views: 113

### Re: lewis vs. bronsted

Bronsted acids donate protons whereas Lewis acids take in protons, or rather, accept them. Do not confuse protons with electrons here!
Sun Nov 24, 2019 5:56 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why are inorganic acids stronger?
Replies: 8
Views: 111

### Re: Why are inorganic acids stronger?

Inorganic compounds can lose their hydrogen ions more easily, which makes them stronger as an acid.
Sun Nov 24, 2019 5:55 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Molecular shape vs Electron Configuration
Replies: 4
Views: 95

### Re: Molecular shape vs Electron Configuration

I like to think of arrangement and shape as two separate things, where the shape is determined by the geometry and the arrangement is depended on electrons, which includes the electron configuration.
Sun Nov 24, 2019 5:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: square planar vs tetrahedral
Replies: 5
Views: 66

### Re: square planar vs tetrahedral

I found it extremely helpful to make a chart with the steric number as the “y-axis” and the number of lone pairs as the “x-axis” for the molecular shapes. This would make the difference between shapes more obvious.
Sun Nov 24, 2019 5:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape
Replies: 29
Views: 737

### Re: Bent Shape

A bent shape will have only one or two lone pairs, with VESPR functions AX2E or AX2E2.
Sun Nov 24, 2019 5:44 pm
Forum: Electronegativity
Topic: Increasing/Decreasing Electronegativity
Replies: 9
Views: 212

### Re: Increasing/Decreasing Electronegativity

I like to remember that fluorine is the most electronegative, and this gives a hint as to which direction electro negativity increases/decreases.
Sun Nov 24, 2019 5:42 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: pi and sigma bonds
Replies: 4
Views: 79

### Re: pi and sigma bonds

Sigma bonds overlap end to end while pi bonds overlap side to side, and sigma bonds are able to rotate do to the way they overlap generally.
Tue Nov 19, 2019 9:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Can linear molecular shapes have lone pair?
Replies: 4
Views: 58

### Re: Can linear molecular shapes have lone pair?

I found it useful to create a chart of shape with the steric number being the "y-axis" and the number of lone pairs being the "x-axis", and this would show that for AX2E3 and AX2E, the shape is linear and the angle is 180.
Tue Nov 19, 2019 9:34 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: polarizability of anions
Replies: 3
Views: 62

### Re: polarizability of anions

Larger molecules are typically more polarizable than smaller ones, meaning that polarizability decreases from left to right and increases as you go down the periodic table.
Tue Nov 19, 2019 9:28 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-Dipole
Replies: 5
Views: 100

### Re: Dipole-Dipole

If the dipole moments cancel each other out, the molecule is no longer polar, it is non-polar, and there is no dipole moment. I like to consider this in terms of electronegativity and the relative charges on molecules, instead of just memorizing facts.
Tue Nov 19, 2019 9:25 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: Hydrogen bonding
Replies: 3
Views: 49

### Re: Hydrogen bonding

N, O, and F each have very high electronegativity, with F being the highest, which allows for the dipole moment to be created when they bond with hydrogen, which is not very electronegativity.
Sun Nov 03, 2019 7:52 pm
Forum: Formal Charge and Oxidation Numbers
Topic: When to calculate formal charge
Replies: 7
Views: 97

### Re: When to calculate formal charge

I do not think it is absolutely necessary every time, but it is a good way to check that the lewis structure is the best possible for the molecule.
Sun Nov 03, 2019 7:49 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Stability
Replies: 3
Views: 73

### Re: Formal Charge Stability

Since atoms are most stable when they share their valence electrons equally in bonding, and valence electrons is the first term in the formal charge formula, if the formal charge is 0, the previously stated will be fulfilled, making it more stable.
Sun Nov 03, 2019 7:43 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge purpose
Replies: 40
Views: 2633

### Re: Formal charge purpose

Especially when dealing with resonance, finding the formal charge of each lewis structure is essential to determining the most stable structure, with a formal charge of 0 or as close to 0 as possible.
Sun Nov 03, 2019 7:39 pm
Forum: Bond Lengths & Energies
Topic: Strength of Bonds
Replies: 16
Views: 207

### Re: Strength of Bonds

Shorter bonds are stronger. Double and triple bonds are shorter than single bonds, so these types of bonds are stronger.
Sun Nov 03, 2019 7:34 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength
Replies: 6
Views: 58

### Re: Bond Strength

When the bond length is shorter, as with double and triple bonds, which involve more electrons being shared between atoms, the atoms are closer together, and there is a stronger energy due to the atomic radii in relation to the distance between the nuclei of each atom being shorter, making the pull ...
Sat Oct 26, 2019 11:52 pm
Forum: Ionic & Covalent Bonds
Topic: How are lewis structures filled?
Replies: 6
Views: 60

### Re: How are lewis structures filled?

I agree that it is best to think of the drawing of lewis dot structures as similar to electron configurations, following Hund's rule in the distribution of dots/arrows.
Sat Oct 26, 2019 11:39 pm
Forum: Ionic & Covalent Bonds
Topic: "Delocalized" Electrons
Replies: 5
Views: 76

### Re: "Delocalized" Electrons

I agree with the responses already given, but I would also like to add that I find it easier to think of delocalized as a synonym for mobile, meaning the electrons can move around, hence resonance.
Sat Oct 26, 2019 11:22 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance
Replies: 12
Views: 191

### Re: Resonance

Compounds with resonance are more stable because their electrons are delocalized, or more mobile, which leads to a lower overall energy since the electrons occupy a greater volume.
Sat Oct 26, 2019 11:19 pm
Forum: Ionic & Covalent Bonds
Topic: lewis structures for diff bonds
Replies: 5
Views: 93

### Re: lewis structures for diff bonds

Yes, and I agree with what has already been said. Just wanted to add that I find drawing the lewis dot structures helps tremendously with understanding the exact exchange/sharing of electrons that is occurring with each bond!
Sat Oct 26, 2019 11:15 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic and Covalent Bonds
Replies: 5
Views: 72

### Re: Ionic and Covalent Bonds

Drawing Lewis dot structures definitely helps in depicting both of these types of bonds. In an ionic bond, between a metal and a nonmetal, one atom gives up an electron to make both atoms more stable, and this is shown with anion and cation depictions(+/-). In a covalent bond, between nonmetals, two...
Sun Oct 20, 2019 8:49 pm
Forum: Trends in The Periodic Table
Topic: electronegativity
Replies: 10
Views: 2535

### Re: electronegativity

It can also be added that electronegativity has an inverse relationship with atomic radius, therefore has an opposite periodic trend. This is because a larger atomic radius usually means more shielding experienced by the nucleus, giving it less affinity for attracting electrons from other atoms.
Sun Oct 20, 2019 8:41 pm
Forum: Trends in The Periodic Table
Topic: ionization energy
Replies: 11
Views: 503

### Re: ionization energy

A good way to remember what this is would be to relate its trends to the trends in atomic radius since the larger the atomic radius, the greater the ionization energy, so their trends line up since they are in direct relationship with one another.
Sun Oct 20, 2019 8:38 pm
Forum: Trends in The Periodic Table
Topic: Study Buddies?
Replies: 8
Views: 105

### Re: Study Buddies?

I'm in! My email is Tahlia.rose46@gmail.com.
Sun Oct 20, 2019 8:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Pauli Exclusion Principle
Replies: 9
Views: 515

### Re: Pauli Exclusion Principle

The Pauli Exclusion Principle basically states that each orbital can only have two electrons, and since they are in the same orbital, these electrons must have opposite spins, which is shown by the arrows pointing in the opposite direction.
Sun Oct 20, 2019 8:28 pm
Forum: Trends in The Periodic Table
Topic: Atomic radii
Replies: 9
Views: 136

### Re: Atomic radii

I think it is important to stress theft that the electrons are being added to the same shell when moving from left to right, therefore the atomic radius does not increase too drastically. At the same time, there are more protons in the nucleus, pulling the electrons in closer, decreasing the atomic ...
Sun Oct 20, 2019 8:19 pm
Forum: Quantum Numbers and The H-Atom
Topic: Orbitals
Replies: 4
Views: 60

### Re: Orbitals

This is also consistent in observing the atomic radius. The more shielding of electrons/the more orbitals, the larger the atomic radius.
Sun Oct 20, 2019 8:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hund's rule and Pauli Exclusion Principle
Replies: 14
Views: 224

### Re: Hund's rule and Pauli Exclusion Principle

Both Hund's Rule and Pauli Exclusion Principle provide the guidelines of the ground state electron configuration for a given atom. Singularly, Hund's Rule provides that each orbital must include one arrow before doubling up. The Pauli Exclusion Principle states that two electrons in the same orbital...
Sun Oct 13, 2019 7:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shielding [ENDORSED]
Replies: 15
Views: 1009

### Re: Shielding[ENDORSED]

Since the 2s orbital is closest to the nucleus, the 2p orbital experiences shielding from the nucleus, increasing the diameter of the atom.
Sun Oct 13, 2019 7:51 pm
Forum: Photoelectric Effect
Topic: Electrons ejected based on wavelength
Replies: 3
Views: 62

### Re: Electrons ejected based on wavelength

A longer wavelength has a lower frequency, since they have an inverse relationship, and a higher frequency is more effective in reaching the required threshold energy to emit an electron from a given metal surface, which would mean the wavelength is shorter.
Sun Oct 13, 2019 7:36 pm
Forum: Photoelectric Effect
Topic: Energy of Photon Clarification
Replies: 4
Views: 105

### Re: Energy of Photon Clarification

A good way for me to remember it is that the energy of the photon has to be equal to the or greater than the energy required, calculated by the work function, to emit the electron.
Sun Oct 13, 2019 7:32 pm
Forum: Photoelectric Effect
Topic: Avogadro's number
Replies: 7
Views: 120

### Re: Avogadro's number

Just a note, Avogadro’s number is actually 6.022*10^23 while planck’s constant is 6.626*10^-34, not to be mixed up! However, these are provided on tests since they are constants.
Sun Oct 13, 2019 7:13 pm
Forum: Einstein Equation
Topic: Planck's constant
Replies: 9
Views: 220

### Re: Planck's constant

Planck’s constant is a vital component of the e=hv equation because it relates the amount of energy emitted to the speed, is with units J.s
Sun Oct 13, 2019 7:02 pm
Forum: Einstein Equation
Topic: E=hv
Replies: 8
Views: 119

### Re: E=hv

h is planck’s constant, which is 6.626*10^-34, and I like to remind myself that it is an extremely small number when I am making calculations.
Sun Oct 13, 2019 6:54 pm
Forum: Limiting Reactant Calculations
Topic: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
Replies: 68
Views: 3898

### Re: Showing Work for Limiting Reactant Calculations on Tests[ENDORSED]

When showing work, I always include units from beginning to end, which makes it easier for the grader to follow as well as serves as a way to check if I got the right answer based on getting down to the right units.

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