Search found 102 matches
- Sun Mar 14, 2021 9:50 pm
- Forum: Student Social/Study Group
- Topic: It is possible to study for the final in one day?
- Replies: 44
- Views: 3814
Re: It is possible to study for the final in one day?
I did that the day before the final. Only advise to do so if you already have a decent foundation on the topics and were paying attention during all the lectures.
- Sun Mar 14, 2021 9:48 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 7836
Re: What was your favorite chem topic?
I enjoyed quantum and I like anything that is math-oriented.
- Sun Mar 14, 2021 9:45 pm
- Forum: Student Social/Study Group
- Topic: Spring Quarter
- Replies: 60
- Views: 2849
Re: Spring Quarter
Starting O-Chem with Chem 30 o.0. Wishing everyone good luck on their future classes.
- Sun Mar 14, 2021 9:43 pm
- Forum: Student Social/Study Group
- Topic: How to Reduce Nervousness before getting results
- Replies: 63
- Views: 4570
Re: How to Reduce Nervousness before getting results
Just know that regardless of what score you get, it won't define you. If you do see a score you do not like, just know that you'll forget about that score months from now. It is not the end all be all! As long as you know you put in your best work, you should be proud.
- Sun Mar 14, 2021 9:40 pm
- Forum: General Rate Laws
- Topic: Factors Affecting k
- Replies: 83
- Views: 4448
Re: Factors Affecting k
Just temperature :)
- Sun Mar 07, 2021 9:15 pm
- Forum: Zero Order Reactions
- Topic: Overall order of the reaction
- Replies: 45
- Views: 1662
Re: Overall order of the reaction
Overall order of the reaction equals the sum of all the orders of the reactants.
- Sun Mar 07, 2021 9:14 pm
- Forum: Student Social/Study Group
- Topic: What do you miss / What are you looking forward to?
- Replies: 92
- Views: 7870
Re: What do you miss / What are you looking forward to?
Just meeting new people and socializing! It gets lonely on zoom uni.
- Sun Mar 07, 2021 9:07 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: integrated rate equations
- Replies: 4
- Views: 254
Re: integrated rate equations
If you have trouble memorizing ([M] vs time is zero; ln[M] vs time is first; 1/[M] vs time is second) then it would be best to derive from the integral using the rate law (-d[A]/dt) and the differential rate law (k[A]m) like how Dr. Lavelle does in the lectures.
- Sun Mar 07, 2021 9:02 pm
- Forum: General Rate Laws
- Topic: Units
- Replies: 10
- Views: 401
Re: Units
Since the units of the rate law are the same, then the units for K has to change depending on whether the reaction is zero order (no M), first order (M), or second order (M^2).
- Sun Mar 07, 2021 8:58 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in ∆G = -nFE
- Replies: 80
- Views: 3648
Re: n in ∆G = -nFE
The n is the moles of electrons transferred. This can be found by figuring out the oxidation numbers of the reactants and products, making two half reactions, and determining the amount of electrons introduced or released in each half reaction.
- Sun Feb 28, 2021 10:40 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Acidic Versus Basic Solutions
- Replies: 20
- Views: 802
Re: Balancing Acidic Versus Basic Solutions
Acid uses hydronium to balance the H and basic uses hydroxide. They both use water to balance O.
- Sun Feb 28, 2021 10:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: [CHEM 14B KARAOKE]
- Replies: 68
- Views: 5419
Re: [CHEM 14B KARAOKE]
Bring your pipes :)
- Sun Feb 28, 2021 9:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling W7/8 #7
- Replies: 3
- Views: 213
Re: Sapling W7/8 #7
I think Mackenzie is right
- Sun Feb 28, 2021 9:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: X electrode and Y electrode
- Replies: 4
- Views: 261
Re: X electrode and Y electrode
I believe for the anode, since electrons are leaving, the solid turns to the aqueous form of the element and enters the solution (Ex. Ag to Ag + assuming the anode is Silver). Since the cathode is in a solution with aqueous ions, the electron from the anode reduces the ions in solution adding to the...
- Sun Feb 28, 2021 9:42 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E vs E naught
- Replies: 36
- Views: 1437
Re: E vs E naught
E naught signifies standard conditions (1 M, 25 C, 1 atm) and does not get affected by change in concentrations, unlike E.
- Sun Feb 21, 2021 11:20 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: deltaU=deltaH+w
- Replies: 8
- Views: 555
Re: deltaU=deltaH+w
Constant pressure since qp=deltaH
- Sun Feb 21, 2021 11:10 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Which R Values to use
- Replies: 22
- Views: 7844
Re: Which R Values to use
It helps to know your units and write them out so you know if the R-value chosen cancels the units out.
- Sun Feb 21, 2021 11:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cathode/Anode
- Replies: 3
- Views: 166
Re: Cathode/Anode
All I know is that the anode is for oxidation and the cathode is for reduction. Since conventionally speaking, oxidation is the left cell and reduction is the right, you can think of it as anode is the left and the cathode is on the right.
- Sun Feb 21, 2021 11:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Classes for Biochem Majors
- Replies: 6
- Views: 436
Classes for Biochem Majors
Hello fellow Biochem majors. I was checking the handbook that we were given during orientation and it suggests I take chem 30A next quarter. However, when I check the pre-reqs of the class, it does not list chem 14B as one? Would I still be able to take this class? Thanks for the help in advance! :)
- Sun Feb 21, 2021 10:56 pm
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 25341
Re: Fave food
I am craving some Alaskan King crab.
- Sun Feb 14, 2021 10:43 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: ΔH
- Replies: 14
- Views: 566
Re: ΔH
If you recall the sapling homework, if both delta H and delta S are positive, then the equation would be deltaG = deltaH - TdeltaS. In order to label a reaction spontaneous, deltaG must be negative. At low temperatures, -TdeltaS might not have a high enough magnitude to overcome deltaH and result in...
- Sun Feb 14, 2021 10:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: What are the three ways to find Delta H?
- Replies: 7
- Views: 12077
Re: What are the three ways to find Delta H?
Hess's law, bond enthalpies (least accurate), and standard enthalpies of formation.
- Sun Feb 14, 2021 10:35 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Delta G and Spontaneity
- Replies: 10
- Views: 719
Re: Delta G and Spontaneity
A positive delta G denotes the need for energy for the reaction, thus indicating it is not spontaneous (occurring without external energy).
- Sun Feb 14, 2021 10:21 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: What's the difference between delta G and delta G°
- Replies: 7
- Views: 15968
Re: What's the difference between delta G and delta G°
Would it be analogous to Q and K, where Q is G and K is Go
- Sun Feb 14, 2021 10:18 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Determining the Sign of S
- Replies: 8
- Views: 389
Re: Determining the Sign of S
If you are talking about S, then it is only positive values. If you are talking about delta S (which I assume you are), then it would depend on the values used in the equation to derive delta S. You can also think of it conceptually (if it is a phase change from solid to liquid or gas, then degenera...
- Sun Feb 07, 2021 11:07 pm
- Forum: Student Social/Study Group
- Topic: Post Midterm 1...
- Replies: 39
- Views: 1518
Re: Post Midterm 1...
Go to as many workshops as you can (I know, sounds a lot like Lavelle, but they really help!)
- Sun Feb 07, 2021 11:05 pm
- Forum: General Science Questions
- Topic: Careless Mistakes
- Replies: 54
- Views: 3112
Re: Careless Mistakes
I would just say take your time and review your work once or twice. And if it is any consolation, the midterms and final will be multiple choice so if you do not see your answer, you know there may be a calculation mistake.
- Sun Feb 07, 2021 11:04 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling Week 3/4 #20
- Replies: 3
- Views: 107
Re: Sapling Week 3/4 #20
Because it is at constant volume. Normally, the change in internal energy would equal work plus q. However, since constant volume denotes no change in volume, work, or
-PdeltaV equals zero. Hope this makes sense.
-PdeltaV equals zero. Hope this makes sense.
- Sun Feb 07, 2021 10:56 pm
- Forum: Student Social/Study Group
- Topic: Superbowl Sunday
- Replies: 26
- Views: 1315
Re: Superbowl Sunday
Sadly it was a pretty disappointing game by the Chiefs. :(
- Sun Feb 07, 2021 10:53 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Relationship between constant volume heat capacity and constant pressure heat capacity.
- Replies: 1
- Views: 91
Relationship between constant volume heat capacity and constant pressure heat capacity.
Can someone explain the relationship between CV and CP. In Sapling, they say that CP = CV+R. However, other sources, including my TA's discussion say that it is CP = CV+nR. Can someone clarify this? Thank you.
- Sun Jan 31, 2021 10:23 pm
- Forum: Student Social/Study Group
- Topic: Go treat yourself after MT1!
- Replies: 75
- Views: 3938
Re: Go treat yourself after MT1!
Definitely need to focus on yourself holistically. Know that these 12-14 questions should not ruin your week!
- Sun Jan 31, 2021 10:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Making X negligible
- Replies: 34
- Views: 1182
Re: Making X negligible
When the equilibrium constant is smaller than 10^-4, then you can try. Of course, after trying, check to see if the x value is less than 5% of the initial concentration.
- Sun Jan 31, 2021 10:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: is HClO3 weak or strong? [ENDORSED]
- Replies: 49
- Views: 3853
Re: is HClO3 weak or strong? [ENDORSED]
It helps to memorize the strong acids with this mnemonic: SO I BRought NO CLean CLOthes. Of course you'll also have to remember an additional CLO in HCLO3
- Sun Jan 31, 2021 10:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Kc
- Replies: 36
- Views: 1183
Re: K vs. Kc
K refers to Kp
- Sun Jan 31, 2021 10:06 pm
- Forum: Student Social/Study Group
- Topic: Best kdrama?
- Replies: 30
- Views: 1737
Re: Best kdrama?
Descendants of the Sun
- Sat Jan 23, 2021 11:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: bonds and energy
- Replies: 13
- Views: 606
Re: bonds and energy
Heat is given off in the formation of bonds because energy is given off in the formation of bonds.
- Sat Jan 23, 2021 11:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: No Heat Change
- Replies: 15
- Views: 508
Re: No Heat Change
The temperature stays the same because the heat is used to break bonds and thus change phases.
- Sat Jan 23, 2021 11:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Do concentrations change at equilibrium?
- Replies: 9
- Views: 153
Re: Do concentrations change at equilibrium?
A change in concentrations is considered a stress and the system will work to minimize this stress (add more products or reactants). Otherwise, equilibrium denotes unchanging concentrations.
- Sat Jan 23, 2021 11:35 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard State
- Replies: 11
- Views: 383
Re: Standard State
Standard state of an element refers to the most stable phase at 1 ATM and the temperature of interest (usually 25 degrees Celsius).
- Sat Jan 23, 2021 11:31 pm
- Forum: Phase Changes & Related Calculations
- Topic: Vapor vs gas
- Replies: 121
- Views: 8303
Re: Vapor vs gas
So then what would be the difference between vaporization and evaporation? Are they one in the same or are there differences?
- Sun Jan 17, 2021 11:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What makes a weak acid?
- Replies: 11
- Views: 252
Re: What makes a weak acid?
It is best to memorize as I think it is difficult to derive from knowing the qualifications. That being said, a weak acid will not lose hydrogen protons easily. Additionally, a weak acid will not result in a stable anion. And weak acids typically have short, strong bonds.
- Sun Jan 17, 2021 11:17 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q > K, Q< K
- Replies: 25
- Views: 703
Re: Q > K, Q< K
Basically, if Q is greater than K, that means that there are more products for Q than K (since products are at the numerator). According to Le Chatelier's principle, when a stress is applied to a system, the system works to counteract it. In this case, when there are more products, then the reaction...
- Sun Jan 17, 2021 11:14 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: q vs k
- Replies: 62
- Views: 2319
Re: q vs k
Q is the products over reactants at any time of the reaction. If Q=K, then the reaction is at equilibrium. If not, you can determine where the reaction will go to (the products side or the reactants side).
- Sun Jan 17, 2021 11:11 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Conjugate acid/base
- Replies: 3
- Views: 158
Re: Conjugate acid/base
It is best to think of it in terms of KaxKb=Kw. A stronger acid means a higher Ka value. But, when looking at the aforementioned equation, a higher Ka means Kb will be lower.
- Sat Jan 16, 2021 11:07 pm
- Forum: Student Social/Study Group
- Topic: Motivation
- Replies: 39
- Views: 1653
Re: Motivation
I feel like you should find spaces where you can have fun. Once you do that, you can apply this mentality: "Work hard, play hard". I find myself grinding the week and then looking forward to zoom calls with friends or game nights. This way, I feel like I have earned it.
- Sun Jan 10, 2021 10:05 pm
- Forum: Student Social/Study Group
- Topic: Study Tips
- Replies: 32
- Views: 1032
Re: Study Tips
-Attend UA workshops -Go to study halls with chem 14b students -Figure out your strengths and weaknesses per unit and watch videos to strengthen those weaknesses -Peruse chemistry community (if you have a question it is likely that someone else has and posted that same question on chem community) -A...
- Sun Jan 10, 2021 9:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K Favors Products or Reactants
- Replies: 20
- Views: 537
Re: K Favors Products or Reactants
Large K values are anything above 10^3 and small K values are anything below 10^-3
- Sun Jan 10, 2021 9:47 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: reaction quotient
- Replies: 6
- Views: 268
Re: reaction quotient
The reaction quotient tells us if the reaction is at equilibrium or not (if Q=K). If the reaction is not at equilibrium, the reaction quotient also tells us what side of the equation will the reaction work to form (reactants to products or products to reactants).
- Sun Jan 10, 2021 9:33 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in Pressure
- Replies: 9
- Views: 175
Re: Change in Pressure
Like many have stated, changing pressure changes concentration because of the change in volume associated. However, not all changes to pressure result or is the result of a change in volume (i.e. adding an inert gas).
- Sun Jan 10, 2021 9:29 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 19
- Views: 1201
Re: Le Chatelier's Principle
Le Chatelier's principle states that when a stress is applied to a system at equilibrium, the system would react to mitigate the stress. To visualize it more easily, think of an aquarium tank with a divider in the middle and both sides having equal water. If you fill more water on one side, the wate...
- Fri Dec 11, 2020 10:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent vs Angular
- Replies: 20
- Views: 830
Re: Bent vs Angular
Bent and angular refer to the same molecular geometry (AX2E, AX2E2)
- Fri Dec 11, 2020 10:24 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: Textbook 3f 5
- Replies: 6
- Views: 336
Re: Textbook 3f 5
You are right that CH3F has a higher dipole moment. However, size and weight trump this. Since iodine is larger and heavier than fluorine (not to mention that there are three of them), the molecule will have stronger LDF and thus a higher melting point.
- Thu Dec 10, 2020 12:17 am
- Forum: Identifying Acidic & Basic Salts
- Topic: Why Salts of weak bases produce acidic solutions and salts of weak acids produce basic solutions
- Replies: 1
- Views: 58
Re: Why Salts of weak bases produce acidic solutions and salts of weak acids produce basic solutions
Salts of weak bases produce acidic solutions: When the salt NH 4 Br dissolves in water, it produces the cation (conjugate acid) NH 4 + and the anion (conjugate base) Br - . You have to look at the conjugate pair of the cation and anion. Looking at NH 4 + we know that it is derived from the WEAK BASE...
- Thu Dec 10, 2020 12:05 am
- Forum: Bronsted Acids & Bases
- Topic: Determining acidic vs basic
- Replies: 5
- Views: 248
Re: Determining acidic vs basic
To memorize acids you'll just have to memorize (typically they'll have H in the front, but not always). The strong acids are HCl, HBr, HI, H2SO4, HNO3, HClO3, and HClO4. For bases, it's a bit easier. Strong bases are group 1 and 2 hydroxides (OH) and oxides (O).
- Thu Dec 10, 2020 12:00 am
- Forum: Hybridization
- Topic: hybridization
- Replies: 1
- Views: 65
Re: hybridization
Hybridization is used to explain why carbon can form 4 bonds with the 4 hydrogen atoms while only having 2 unpaired electrons (from 2p). Since the normal convention states that covalent bonds will share one electron from each atom, then carbon needs to have four unpaired electrons. For this to happe...
- Sat Dec 05, 2020 5:21 pm
- Forum: Naming
- Topic: oxidation number on sapling question
- Replies: 2
- Views: 115
Re: oxidation number on sapling question
If you remember, coordination compounds are neutral. With the knowledge that chlorine's charge is 1-, you can derive that the coordination complex (anything in brackets) is 1+. When you know that, then use your knowledge of the ligand charges to figure out the charge of the transition metal. In this...
- Sat Dec 05, 2020 5:01 pm
- Forum: Hybridization
- Topic: Unhybridized orbitals
- Replies: 5
- Views: 238
Re: Unhybridized orbitals
I believe unhybridized orbitals arise when there are less regions of electron density than there are valence electrons of the element (but I am only theorizing based on one example: C). When Prof. Lavelle was lecturing about sp2, he used Carbon, an element with four valence electrons. Since there ar...
- Sat Dec 05, 2020 4:53 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Trichloroacetic acid example
- Replies: 4
- Views: 119
Re: Trichloroacetic acid example
An important thing to know is that p=-log 10 . K A (the dissociation constant) is only really calculated for weak acids. That being said, the stronger K A is the stronger the acid is. In remembering that p=-log 10 , we can derive that pK A =-log 10 K A . In other words, when K A is larger, pK A is s...
- Sat Dec 05, 2020 4:46 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: linear same atoms?
- Replies: 6
- Views: 341
Re: linear same atoms?
My preferred method would be to determine the number of electron densities around the central atom and then figure out which ones are bonding pairs and which ones are lone pairs. This requires some memorization or visualization skills. For example, like someone mentioned before, this molecule has fi...
- Sat Dec 05, 2020 2:29 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Strong/Weak acids
- Replies: 5
- Views: 220
Re: Strong/Weak acids
I believe you are correct.
- Sun Nov 29, 2020 12:37 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling #3 Bond Angle
- Replies: 8
- Views: 477
Re: Sapling #3 Bond Angle
You'll just have to memorize. In this case, this results in a square pyramid molecular shape which only has 90 degree bond angles.
- Sun Nov 29, 2020 12:22 am
- Forum: Lewis Structures
- Topic: Preferential Attractions
- Replies: 2
- Views: 100
Re: Preferential Attractions
When Lavelle mentions this in his lecture, he wants us to visualize a cation or an anion (something that produces an electrostatic potential) with the molecule who's polarity we are trying to figure out. When he says preferential attraction, he means which part of the molecule would most likely be a...
- Sun Nov 29, 2020 12:06 am
- Forum: Sigma & Pi Bonds
- Topic: Delocalized π bonds
- Replies: 6
- Views: 204
Re: Delocalized π bonds
I believe resonance would be the only way delocalized pi bonds exist as resonance describes the delocalization of electrons.
- Sat Nov 28, 2020 11:58 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Negative poles of molecules
- Replies: 3
- Views: 235
Re: Negative poles of molecules
Take a look at which is more electronegative. The more electronegative atom is the area which you can consider a negative pole. More specifically, if the net vector of these poles would be where the negative pole is.
- Sat Nov 28, 2020 11:48 pm
- Forum: Hybridization
- Topic: Confused on hybridization conceptually
- Replies: 9
- Views: 580
Re: Confused on hybridization conceptually
Hybridization denotes a hybrid of two orbitals. When this occurs, the bonds that use the unpaired electrons in these hybrid orbitals are all of the same energy level. When you figure out hybridization orbitals used, you can figure out what types of bonds are used and consequently the properties of t...
- Sun Nov 22, 2020 10:58 pm
- Forum: Hybridization
- Topic: Determining Hybridization
- Replies: 4
- Views: 421
Re: Determining Hybridization
AJForte-2C wrote:Do you need to create an afbau diagram in order to properly determine hybridization, or is it not necessary?
It helps to visualize but I don't think it is necessary. So long as you know the electron density regions and number of orbitals in subshells, you can figure it out.
- Sun Nov 22, 2020 10:50 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 and Dipole-Dipole
- Replies: 10
- Views: 767
Re: Dipole-Induced-Dipole and Dipole-Dipole
When it comes to dipole-dipole, both molecules are polar with permanent dipole moments. With dipole-induce-dipole, one is a dipole while the other molecule is not naturally polar. It is only until the electrons of another molecule (in this case the polar one) influence the electrons of the non-polar...
- Sun Nov 22, 2020 10:47 pm
- Forum: Ionic & Covalent Bonds
- Topic: C-H bond polarity
- Replies: 10
- Views: 11368
Re: C-H bond polarity
You would think that because they are far then it'll be polar. However, when you search up an electronegativity chart, hydrogen is only about .35 less electronegative than carbon. Despite its position in the periodic table, hydrogen actually has a decent electronegativity.
- Sun Nov 22, 2020 10:44 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining polar molecules
- Replies: 7
- Views: 296
Re: Determining polar molecules
You'll first determine if polar bonds form. You can figure this out by figuring out if the electronegativity difference between the two atoms is high enough to be considered polar bonds. Next, you will need to determine the net electric dipole moment. To figure this out requires knowing the magnitud...
- Sun Nov 22, 2020 10:37 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Determining Non-Polarity
- Replies: 5
- Views: 234
Re: Determining Non-Polarity
Hi! There has to be a difference in electronegativity to have a polar bond. Further, there has to be an overall separation of charge, so the negatively charged molecules must be on one side. To add on to what Jessica said, if the polar bonds cancel each other (same magnitude and opposite vector dir...
- Tue Nov 17, 2020 11:16 pm
- Forum: Lewis Structures
- Topic: NO2 Polarity
- Replies: 6
- Views: 2543
Re: NO2 Polarity
It is polar because of the electronegativity difference between nitrogen and oxygen. As you may know, electronegativity is the tendency of an atom to attract electrons. Because oxygen has a higher electronegativity than nitrogen, and because the difference is large enough, electrons are closer to th...
- Fri Nov 13, 2020 9:59 pm
- Forum: Ionic & Covalent Bonds
- Topic: Nomenclature
- Replies: 6
- Views: 206
Nomenclature
Should we know how the molecular formulas when given the names of the molecule. For example, in Sapling there is a question where they ask to draw Lewis Structure of phosphate and phosphite ions as well as nitrate and nitrite ions. Should we know these molecular formulas off the top of our heads for...
- Fri Nov 13, 2020 5:16 pm
- Forum: Dipole Moments
- Topic: Dipole-dipole vs. ion-dipole vs. ion-ion
- Replies: 4
- Views: 239
Re: Dipole-dipole vs. ion-dipole vs. ion-ion
Dipole-dipole is when two polar molecules (covalent molecules with unequal sharing of electrons) are attracted together due to electrostatic attraction between a negative and positive dipole. Ionic-dipole is when a cation or anion is attracted to the dipole (negative or positive area due to uneven e...
- Fri Nov 13, 2020 5:09 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2761570
Re: Post All Chemistry Jokes Here
I'm not sure if this was put already but it is my favorite chemistry joke.
"If Iron Man and Silver Surfer teamed up, they'd be alloys."
"If Iron Man and Silver Surfer teamed up, they'd be alloys."
- Thu Nov 12, 2020 7:17 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations
- Replies: 7
- Views: 390
Re: Electron configurations
Also how come Dr. Lavelle said that 4d state is lower energy than 5s state, after 2 e- have occupied 5s state. Based on what you said wouldn't it be the opposite? wouldn't it be that 4d state is lower energy than 5s state before 2 e- have occupied 5s state? When Lavelle says that 4s is lower than 5...
- Thu Nov 12, 2020 6:57 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations
- Replies: 7
- Views: 390
Re: Electron configurations
Sharon Kim 1A wrote:When writing the electron configurations, I understood it to be written as 3d orbitals before the 4s. Is that the same thing as saying 3d orbitals are filled before 4s?
No. That is purely a stylistic decision. It is the same as writing 4s 3d
- Thu Nov 12, 2020 6:28 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations
- Replies: 7
- Views: 390
Re: Electron configurations
From my understanding, electrons will always fill 4s before 3d. This is because 4s is slightly lower in energy than 3d. It is only when the 3d orbital is filled when 4s is greater in energy than 3d. For this reason, electrons are removed from 4s before 3d.
- Fri Nov 06, 2020 11:35 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Isoelectric atoms
- Replies: 9
- Views: 596
Re: Isoelectric atoms
Do you mean isoelectronic atoms? If so, then it means having identical electron configurations. So Cl-, Ar, and K+ are all isoelectronic to one another. As for the other characteristics, it depends on whether the trend is affected by the nuclear charge or the atomic radius (how many orbitals). Sorry...
- Fri Nov 06, 2020 1:11 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Lavelle Lecture 11/6
- Replies: 2
- Views: 115
Re: Lavelle Lecture 11/6
When Lavelle says this, he is referring to the unequal sharing of electrons. If you look at models (search up polar covalent bonds) depicting this, you can see electrons closer to one atom than the other. This results in a negative dipole.
- Fri Nov 06, 2020 1:06 pm
- Forum: SI Units, Unit Conversions
- Topic: Modules This Week
- Replies: 9
- Views: 489
Re: Modules This Week
Sadly it doesn't seem like Professor Lavelle updated his modules after the Heisenberg Uncertainty Principle one. He did say that if we enjoy them, he will be willing to create more.
- Fri Nov 06, 2020 12:01 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Change after Z=20
- Replies: 2
- Views: 63
Re: Change after Z=20
hi! so if you notice on the periodic table, after atomic number 20, we encounter the transitional metals in the d-block. if you can recall from Dr. Lavelle's lectures, this transition to the d-block is significant because in contrast to what we would expect, where an increase in n, the energy level...
- Fri Nov 06, 2020 11:53 am
- Forum: Octet Exceptions
- Topic: Octet exceptions
- Replies: 4
- Views: 116
Re: Octet exceptions
From my understanding of the lectures, elements greater than or equal to n=3 can have more than 8 electrons. This is because, when thinking about quantum numbers, you can only have l=2 if n is greater than or equal to 3 (l= 0,1... n-1). And when you have l=2, electrons can fill the d-orbital allowin...
- Sat Oct 31, 2020 6:49 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Textbook 1D.13
- Replies: 3
- Views: 64
Re: Textbook 1D.13
For part a, l starts at 0 and can only go up to n-1. So this means a max of l=6. The values will be l= 0,1,2,3,4,5,6 (7 values). As for ml, it is the values of -l to l. In this case, the l value for d is 2. So the ml will be -2,-1,0,1,2. This corresponds with the 5 orbitals in the d subshell.
- Sat Oct 31, 2020 6:13 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Exceptions to Electron Configuration Rules
- Replies: 2
- Views: 130
Re: Exceptions to Electron Configuration Rules
I believe those are the two main exceptions. I wouldn't know of any more, especially any others Professor Lavelle mentioned.
- Sat Oct 31, 2020 6:11 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Subshells in Sapling HW #25
- Replies: 2
- Views: 124
Re: Electron Subshells in Sapling HW #25
I think you are correct in your line of reasoning. It may be that the increased nuclear charge accounts for the size of the atomic radius more than the subshells of the valence electrons.
- Sat Oct 31, 2020 6:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: Main group elements
- Replies: 8
- Views: 614
Re: Main group elements
I think they are the groups (columns) 1 and 2 and 13-18. The rest are transition metals and inner transition metals (the two rows at the bottom). As for why they are called main group elements, I am not sure.
- Sat Oct 31, 2020 5:50 pm
- Forum: Trends in The Periodic Table
- Topic: Oxygen and Ionization Energy
- Replies: 9
- Views: 501
Re: Oxygen and Ionization Energy
The ionization energy trend is based on how easy it is to remove the electron. Having a greater nuclear charge makes it harder to remove the electron. So, fluorine having a higher ionization energy than oxygen follows the trend. However, the exception can be seen in nitrogen, in which case nitrogen ...
- Fri Oct 23, 2020 12:13 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Atomic Spectra Post-Module Assessment
- Replies: 4
- Views: 196
Re: Atomic Spectra Post-Module Assessment
I am pretty sure it is the second one. This is because longer wavelength equates to less energy, and the energy disparity between n=4 and n=2 is greater than from n=5 to n=1.
- Fri Oct 23, 2020 12:09 am
- Forum: General Science Questions
- Topic: When to use sig figs
- Replies: 19
- Views: 674
Re: When to use sig figs
I usually write out the full number each time and then apply the sig figs at the end. That way, I can ensure I get the most accurate number.
- Wed Oct 21, 2020 2:31 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Lecture 10/21 Question about H-atom problem
- Replies: 3
- Views: 156
Re: Lecture 10/21 Question about H-atom problem
That is just the value of the mass of an electron.
- Wed Oct 21, 2020 2:29 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Which Equation should we use?
- Replies: 3
- Views: 167
Re: Which Equation should we use?
Well Lavelle did introduce the former so I would just stick to that.
- Mon Oct 19, 2020 2:25 pm
- Forum: Properties of Light
- Topic: Photoelectric Experiment
- Replies: 2
- Views: 97
Re: Photoelectric Experiment
In fact, this observation that increasing the intensity does not cause ejection of an electron proves that light has this duality of wave and particle. If light only acted as a wave, then increasing the intensity should have ejected the electron (just like how higher ocean waves have a higher knockb...
- Fri Oct 16, 2020 6:01 pm
- Forum: Einstein Equation
- Topic: wave vs. photons
- Replies: 4
- Views: 239
Re: wave vs. photons
I believe that all objects have this wave-particle duality. The only reason we don't see it in objects like baseballs or cars is because the momentum of these objects results in a small wavelength (when plugged into the DeBriglie equation). This wavelength is too small for us to register that the ob...
- Fri Oct 16, 2020 5:50 pm
- Forum: DeBroglie Equation
- Topic: Problem 1B.15
- Replies: 3
- Views: 87
Re: Problem 1B.15
Taylor K 2C wrote:I believe it is because kg is the fundamental SI unit for mass. But I'm not sure.
Yes. Kg are the standard SI units along with meters for length and seconds for time (to name a few more).
- Thu Oct 15, 2020 3:48 pm
- Forum: Photoelectric Effect
- Topic: Frequency vs. Intensity
- Replies: 16
- Views: 571
Re: Frequency vs. Intensity
I liked the analogy Dr. Lavelle gave in his lecture. It is sort of like a cross country team. No matter how many members you have, if not one of them can jump the hurdle, the team is not going to win.
- Wed Oct 14, 2020 12:06 pm
- Forum: Properties of Light
- Topic: Light intensity for electron ejection
- Replies: 7
- Views: 287
Re: Light intensity for electron ejection
Professor Lavelle mentioned in the module pertaining to this topic that if you were to double the intensity (double the photons), then you would also double the electrons emitted. Thus, it can be seen in a 1:1 ratio, that is if the energy per photon is high enough.
- Tue Oct 13, 2020 4:05 pm
- Forum: DeBroglie Equation
- Topic: DeBroglie Concept Help
- Replies: 4
- Views: 217
Re: DeBroglie Concept Help
Hello! From my understanding of the lectures, De Broglie's concept explain that any moving particle with a momentum has wave properties and so all matter has wave like properties. We only notice these properties in small objects with a high velocity since those with a higher mass (like the baseball...
- Thu Oct 08, 2020 7:11 pm
- Forum: Significant Figures
- Topic: How to deal with significant figures in decimals with zeros.
- Replies: 20
- Views: 1104
Re: How to deal with significant figures in decimals with zeros.
20.01 has 4 sig figs. As for your base question, when there is a decimal point, all trailing zeros are counted in the sig fig count. However, when there is no decimal point, trailing zeros don't matter. Any zero in between numbers counts, regardless if there is a decimal. So 2001 will also be 4 sig ...
- Wed Oct 07, 2020 2:45 pm
- Forum: Significant Figures
- Topic: Week 1 Homework #7
- Replies: 3
- Views: 185
Week 1 Homework #7
The problem tells us that a solution of CaCl2 in water forms a mixture that is 42.0% calcium chloride. It gives us the total grams of the solution (494.6 g) and asks what is the grams for water and calcium chloride. For the sake of the sig figs, I took into account the 42.0% and decided to round my ...
- Wed Oct 07, 2020 2:31 pm
- Forum: Significant Figures
- Topic: When are sig figs applied?
- Replies: 12
- Views: 241
Re: When are sig figs applied?
As everyone has stated above, round sig figs at the very end. This way, you prevent any inaccuracy by rounding per step. It may seem tedious to write out the full number every step, but it is needed to ensure accuracy.