Search found 65 matches

by Andrew Wang 1C
Wed Jan 20, 2021 12:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61 PART B
Replies: 3
Views: 10

Re: 5.61 PART B

When changing the pressure, we only look at the number of moles of gas. In this case there are 6 moles of gas on each side, so there is no change.
by Andrew Wang 1C
Wed Jan 20, 2021 11:37 am
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 34
Views: 99

Re: Endothermic v. Exothermic

I assume that's the case, since the sign of delta H is kind of "built in" to the definitions of endothermic and exothermic. Negative delta H means heat is released, so it's exothermic, while positive means heat is absorbed which is endothermic.
by Andrew Wang 1C
Tue Jan 19, 2021 6:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Exams
Replies: 7
Views: 78

Re: Midterm Exams

Yeah they'll most likely be the same as last quarter where we take it in breakout rooms with TA's. And it's fine if your laptop doesn't have a camera, we used our phones for the zoom last quarter too while taking the test on computer.
by Andrew Wang 1C
Tue Jan 19, 2021 3:01 pm
Forum: Bronsted Acids & Bases
Topic: Difference Between Amphoteric and Amphiprotic
Replies: 3
Views: 17

Re: Difference Between Amphoteric and Amphiprotic

Amphoteric compounds can act as both acids and bases. One example of an amphoteric compound is Al2O3, which can act as a Lewis acid and base despite not having any protons (H+) to donate. Amphiprotic compounds can act as both proton donors and acceptors (you can remember this by the "protic&quo...
by Andrew Wang 1C
Tue Jan 19, 2021 2:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka2 << Ka1
Replies: 5
Views: 33

Re: Ka2 << Ka1

The previous answers all explained it very well! I just wanted to add that you can ignore Ka2 for most acids except H2SO4 (this shows up in a textbook problem)
by Andrew Wang 1C
Wed Jan 13, 2021 5:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B.11 Question
Replies: 2
Views: 19

Re: 6B.11 Question

Using the pH, you can find the current (diluted) concentration of OH-. Then you can use M1V1=M2V2 to find the concentration of the original solution. Using the concentration you found, you can figure out the moles of NaOH, then use molar ratios and stoichiometry to find the mass of Na2O added. Hope ...
by Andrew Wang 1C
Tue Jan 12, 2021 10:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook problem 5.57 [ENDORSED]
Replies: 4
Views: 71

Re: Textbook problem 5.57 [ENDORSED]

How I did it was by starting with an ICE table and filling in values for what we know, and using variables for what we don't know. Although it's a bit different for this problem since the variable isn't in the "C" row. This should leave you with one unknown variable, which you can solve fo...
by Andrew Wang 1C
Tue Jan 12, 2021 1:28 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approximation of X in cubic equations
Replies: 5
Views: 23

Re: Approximation of X in cubic equations

I'm pretty sure Kc will always be small on these questions since Dr. Lavelle said we wouldn't be able to algebraically solve cubic equations, so we have to just approximate.
by Andrew Wang 1C
Mon Jan 11, 2021 2:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: ICE Table
Replies: 9
Views: 50

Re: ICE Table

It depends on the value of Q relative to K. If Q is greater than K, then the reaction proceeds towards the reactants, so you would put "-x" on the products side and "+x" on the reactants side. If Q is less than K, then the reaction proceeds towards products and you would put &quo...
by Andrew Wang 1C
Mon Jan 11, 2021 1:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5h #3
Replies: 5
Views: 31

Re: Textbook Problem 5h #3

Use table 5G.2 to find two or more reactions that add together to result in the desired reaction 2BrCl(g+H2(g)⇌Br2(g)+2HCl(g). Then use the equilibrium constants for the reactions that you found in the table to calculate K for the overall reaction by multiplying them together.

Hope this helps!
by Andrew Wang 1C
Fri Jan 08, 2021 11:35 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5G. 1
Replies: 4
Views: 29

Re: Textbook Problem 5G. 1

For (c), the equilibrium constant will not change due to an increase in pressure (or concentration) on one side of the reaction. Equilibrium constants for reactions only change if the temperature is changed. For (d), according to Le Chatlier's principle, if you start with a higher concentration on o...
by Andrew Wang 1C
Thu Jan 07, 2021 11:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW problem
Replies: 4
Views: 51

Re: HW problem

Use table 5G.2 to find two reactions that, when added together, result in the desired reaction 2BrCl(g+H2(g)⇌Br2(g)+2HCl(g). Then you'd use the equilibrium constants for the two reactions that you found in the table to calculate K for the overall reaction by multiplying them together. Hope this helps!
by Andrew Wang 1C
Wed Jan 06, 2021 11:30 am
Forum: Ideal Gases
Topic: K and PV=nRT
Replies: 9
Views: 75

Re: K and PV=nRT

You would use PV=nRT when you are converting from partial pressure to concentration, or vice versa. So if the problem asks for Kc, but gives you a measurement in atm, you would use PV=nRT to convert that value to the concentration and then plug it into Kc=[P]/[R]. For problems that ask for Kp, you'd...
by Andrew Wang 1C
Tue Jan 05, 2021 12:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs Kp
Replies: 14
Views: 73

Re: Kc vs Kp

While Kc and Kp are calculated the same way, I don't think they are equal in value. Kp can be used if the reaction involves only gases, while Kc can be used for gases and aqueous solutions. The problem will usually tell you which one to solve for by looking at the units (moles for Kc, atm or bar for...
by Andrew Wang 1C
Mon Jan 04, 2021 12:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: KC vs KP [ENDORSED]
Replies: 6
Views: 44

Re: KC vs KP [ENDORSED]

It would depend if we are given the values of reactants/products in concentration or bars. I remember some problems in the Audio-Visual modules had us calculate Kc when there were only gases in the reaction.
by Andrew Wang 1C
Wed Dec 09, 2020 10:54 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 2
Views: 26

Re: Rydberg Equation

Yes, you can get the Rydberg equation by setting E=hv equal to the difference between energy levels -(hR)/n2^2 - (-(hR)/n1^2). then you cancel h from both sides to get the equation in the equation sheet. If they were asking you to calculate the energy of a specific level you'd probably use -(hR)/n^2...
by Andrew Wang 1C
Wed Dec 09, 2020 10:47 am
Forum: Student Social/Study Group
Topic: lecture bruincast #29 problem
Replies: 10
Views: 90

Re: lecture bruincast #29 problem

I was having this problem on Monday with lecture 28, and just kept refreshing the page until it played again. It shouldn't take too long for it to work again, though.
by Andrew Wang 1C
Wed Dec 09, 2020 10:44 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Overall Rxn K
Replies: 2
Views: 21

Re: Overall Rxn K

Yes, when you combine (add) the two reactions together you would multiply their individual K's together to get the K of the overall reaction. I think the equilibrium constants will be covered more in-depth in 14B, and for this class just know K A decreases as you remove more protons, and that a high...
by Andrew Wang 1C
Tue Dec 08, 2020 11:23 am
Forum: Lewis Acids & Bases
Topic: general conceptual question
Replies: 9
Views: 72

Re: general conceptual question

I tend to first look at the bond that is being broken when an acid loses a H+, and comparing them to each other. The longer that bond is, the stronger the acid. If the bond being broken is the same across the compounds being compared, I would look at which compound has the more stable anion. There a...
by Andrew Wang 1C
Mon Dec 07, 2020 11:06 am
Forum: Bronsted Acids & Bases
Topic: Acid and Base Reaction
Replies: 1
Views: 15

Re: Acid and Base Reaction

If the reaction involves a strong acid or base, the concentration of H3O+ or OH- will be equal to the concentration of the acid or base, respectively. If it's a weak acid or base then we need to use equilibrium which won't be tested in this course.
by Andrew Wang 1C
Fri Dec 04, 2020 11:16 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HClO vs. HBrO vs. HIO example
Replies: 3
Views: 56

Re: HClO vs. HBrO vs. HIO example

The oxygen atom is common across all three compounds, so you wouldn't use it to compare them to each other. Instead, we use the halogens because they are different in each compound and therefore comparable.
by Andrew Wang 1C
Thu Dec 03, 2020 1:50 pm
Forum: Naming
Topic: Ferrate or iron?
Replies: 8
Views: 45

Re: Ferrate or iron?

My TA gave us some examples of when to use the Latin name for transition metals: Fe (ferrate), Cu (cuprate), Au (aurate). Looks like there's maybe a pattern here to use the Latin name when the atomic symbol isn't an exact abbreviation of its name?
by Andrew Wang 1C
Wed Dec 02, 2020 11:12 am
Forum: Bronsted Acids & Bases
Topic: HCl vs. HBr
Replies: 6
Views: 51

Re: HCl vs. HBr

So would it be true to say that the weaker the bond, the stronger the acid since it dissociates more easily?
by Andrew Wang 1C
Tue Dec 01, 2020 3:08 pm
Forum: Coordinate Covalent Bonds
Topic: Polydentate Ligands
Replies: 8
Views: 66

Re: Polydentate Ligands

I'm not too sure of this myself, but I think one way to do it is to see how many atoms in the ligand have lone pairs, and use that number to determine if it is bidentate, monodentate, etc. Also consider if the ligand can rotate or not (pi bonds), since double bonds may affect how many sites a metal ...
by Andrew Wang 1C
Mon Nov 30, 2020 10:51 am
Forum: Naming
Topic: Using ido or o
Replies: 24
Views: 138

Re: Using ido or o

Hi! In today's lecture, Lavelle told us it was fine to use either, but he used -o in his lectures. -ido is a new naming convention that not many people know about yet.
by Andrew Wang 1C
Fri Nov 27, 2020 3:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: TM "Octet"
Replies: 4
Views: 37

Re: TM "Octet"

Transition metals often don't follow the octet rule since the octet rule only considers the s and p orbitals. Transition metals are located in the d block so they often use their d-orbitals when bonding.
by Andrew Wang 1C
Thu Nov 26, 2020 3:44 pm
Forum: Hybridization
Topic: Sapling #12
Replies: 27
Views: 187

Re: Sapling #12

Finding the hybridization of the oxygen is similar to finding the hybridization of the carbon. You'd look at how many regions of electron density the oxygen atom has (# of bonds + lone pairs), and use that to find the hybridization.

Hope this helps!
by Andrew Wang 1C
Wed Nov 25, 2020 11:29 am
Forum: Biological Examples
Topic: Why Cisplatin is considered "general"
Replies: 4
Views: 55

Re: Why Cisplatin is considered "general"

I'm not sure if this is what you mean by "general" or not, but it could be that cisplatin isn't specific to just cancer cells since it can also affect healthy cells. What you said about it treating many types of cancer also makes sense though!
by Andrew Wang 1C
Tue Nov 24, 2020 10:57 am
Forum: Administrative Questions and Class Announcements
Topic: CHEM14B Asynchronous
Replies: 5
Views: 98

Re: CHEM14B Asynchronous

I think it will be, but Dr. Lavelle doesn't recommend overlapping 14B with another class since the exams might take place during the lecture time.
by Andrew Wang 1C
Mon Nov 23, 2020 10:30 am
Forum: Hybridization
Topic: Unhybridized p orbital
Replies: 2
Views: 51

Unhybridized p orbital

Do all double bonds involve unhybridized p orbitals? What other examples of the unhybridized p orbital should we need to know?
by Andrew Wang 1C
Thu Nov 19, 2020 12:34 am
Forum: Lewis Structures
Topic: NO+
Replies: 3
Views: 30

Re: NO+

A triple bond between the N and O is the only way for both atoms to have a full octet.
by Andrew Wang 1C
Wed Nov 18, 2020 10:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Experimental Determination VSEPR
Replies: 1
Views: 27

Re: Experimental Determination VSEPR

I'm not sure about the specific details of how they are determined, but I remember reading somewhere that scientists can use x-ray or electron diffraction to measure bond angles in different substances.
by Andrew Wang 1C
Tue Nov 17, 2020 10:27 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: electron spin
Replies: 4
Views: 71

Re: electron spin

If an orbital only has one electron and is in the ground state, I'm pretty sure the spin should be +½. It wouldn't be in the ground state if it had spin -½.
by Andrew Wang 1C
Tue Nov 17, 2020 10:24 am
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Boiling and Melting point
Replies: 18
Views: 117

Re: Boiling and Melting point

Boiling and melting points can be related in the sense that both are higher when the substance has stronger intermolecular forces. So yes, a higher melting (and boiling) point means stronger intermolecular forces, since more energy (heat) will be required to overcome the interactions to change phase.
by Andrew Wang 1C
Mon Nov 16, 2020 10:50 am
Forum: Trends in The Periodic Table
Topic: Why don't other np4 elements behave like oxygen in terms of ionization?
Replies: 2
Views: 40

Re: Why don't other np4 elements behave like oxygen in terms of ionization?

Yes, I think the other Group 16 elements are also exceptions to the trend and have lower ionization energies, since they all have 4 electrons in their outermost p orbitals. This makes them have more repulsive interactions, so it takes less energy to remove an electron.
by Andrew Wang 1C
Fri Nov 13, 2020 2:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs
Replies: 6
Views: 68

Re: lone pairs

Lone pairs are only attracted by one nucleus, compared to a bonding pair which is attracted to two. This makes it so that lone pairs have a greater negative charge and thus more repulsion, which accounts for the extra "volume."
by Andrew Wang 1C
Thu Nov 12, 2020 12:24 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: determining viscosity
Replies: 11
Views: 100

Re: determining viscosity

From Dr. Lavelle's most recent lecture, we can determine how viscous a substance is compared to another by analyzing their IMFs. The stronger IMF's something has, the more viscous it will be.
by Andrew Wang 1C
Wed Nov 11, 2020 10:13 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: Sapling #20
Replies: 2
Views: 57

Re: Sapling #20

How I did it was I drew the Lewis structure for CH3CHO and used that to determine which interactions were present. I'm not sure if there's a method to determine by just using the formula, but drawing the Lewis structure should be helpful.
by Andrew Wang 1C
Tue Nov 10, 2020 10:53 am
Forum: Dipole Moments
Topic: melting point
Replies: 4
Views: 40

Re: melting point

Yes, I believe that is the case. Since diethyl ether is nonpolar, it only has induced dipole-induced dipole interactions (LDF) between its molecules. Butanol also has LDF, but will also have dipole-dipole interactions because it is polar. So because of this extra interaction, it requires more energy...
by Andrew Wang 1C
Mon Nov 09, 2020 11:06 am
Forum: Octet Exceptions
Topic: SO42- Octet Rule Exception Orbitals
Replies: 4
Views: 29

Re: SO42- Octet Rule Exception Orbitals

The 4s orbital is filled first before the 3d due to its lower energy. Although this isn't shown in our textbook's electron configurations, there is another way to order them called the "filling order" that shows this more clearly.

Image
by Andrew Wang 1C
Wed Nov 04, 2020 9:36 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Focus 1E #7b
Replies: 2
Views: 24

Re: Focus 1E #7b

Oh I completely missed that the second spin in 2p was pointed down. Thank you!
by Andrew Wang 1C
Wed Nov 04, 2020 9:35 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Element orbital representation
Replies: 4
Views: 74

Re: Element orbital representation

In your example, the electron in the 3d orbital can act as a valence electron and determine how the element reacts, which is why it is important to include it in the noble gas configuration.
by Andrew Wang 1C
Tue Nov 03, 2020 9:53 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Focus 1E #7b
Replies: 2
Views: 24

Focus 1E #7b

I'm confused about how 7b (Nitrogen) is in an excited state. I said that it was in the ground state since it has the electrons in the correct orbitals, but the answer key says otherwise.
by Andrew Wang 1C
Mon Nov 02, 2020 10:59 am
Forum: Lewis Structures
Topic: Lewis Structure for NO3-
Replies: 10
Views: 105

Re: Lewis Structure for NO3-

Each of the single-bonded oxygens has 3 lone pairs, which combined with the single bond gives them a full 8 electron octet. I'm not sure about the "-" in NO3-, but I hope this helps!
by Andrew Wang 1C
Mon Nov 02, 2020 10:50 am
Forum: Formal Charge and Oxidation Numbers
Topic: When to use formal charge or octet rule?
Replies: 12
Views: 104

When to use formal charge or octet rule?

When drawing Lewis structures, how do we know when to use the formal charge or when to use the octet rule for each element?
by Andrew Wang 1C
Fri Oct 30, 2020 11:59 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Shorthand Question
Replies: 5
Views: 44

Re: Electron Configuration Shorthand Question

Generally when shortening electron configuration, we would substitute the preceding noble gas, instead of the immediately preceding element. This allows us to see the electrons in the highest energy level (valence electrons).
by Andrew Wang 1C
Fri Oct 30, 2020 11:57 am
Forum: Properties of Light
Topic: Textbook Question Number 1A 3 c
Replies: 3
Views: 60

Re: Textbook Question Number 1A 3 c

I saw other explanations saying that extent of change refers to amplitude. Can this also be true? I don't think so, since the amplitude corresponds to the electric field. The extent of change refers to the slope from a trough to the next crest on the wave, or vice versa. So while changing the ampli...
by Andrew Wang 1C
Wed Oct 28, 2020 11:27 am
Forum: DeBroglie Equation
Topic: Brooke Yasuda's Wk 2 Workshop
Replies: 1
Views: 48

Re: Brooke Yasuda's Wk 2 Workshop

I think the answer key had the energy of the incident light equal to the work function because the kinetic energy of the ejected electron is so small that it's basically negligible, so adding it to the work function wouldn't change anything. I'm pretty sure either way is fine and gives the same answ...
by Andrew Wang 1C
Tue Oct 27, 2020 11:19 am
Forum: *Shrodinger Equation
Topic: Particle in a Box
Replies: 5
Views: 100

Re: Particle in a Box

I think the amplitude of the wave is 0 at the ends of the box because that's where the box's borders are, so there is no chance that the particle will actually be at that location (since it's already taken by the edges of the box). The wavefunction represents the probability that the particle will b...
by Andrew Wang 1C
Mon Oct 26, 2020 2:40 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic VS Molecular Spectroscopy
Replies: 1
Views: 17

Re: Atomic VS Molecular Spectroscopy

I'm not 100% sure, but I think there are a couple concepts in that learning outcome: one is to understand that you can analyze the spectroscopy of both atoms and molecules, and the second is to understand the differences between Lyman and Balmer series, like how they each correspond to one region an...
by Andrew Wang 1C
Thu Oct 22, 2020 3:48 pm
Forum: Empirical & Molecular Formulas
Topic: Diatomic Elements
Replies: 3
Views: 21

Re: Diatomic Elements

I think you would use the diatomic form in calculations when the diatomic elements are alone (not bonded to anything else). Otherwise, you should use what is given in the chemical equation.
by Andrew Wang 1C
Wed Oct 21, 2020 11:29 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Applied to particles other than electrons
Replies: 5
Views: 23

Re: Applied to particles other than electrons

The Heisenberg indeterminacy equation applies to all objects, but is only noticeable and mostly affects objects on an atomic scale.
by Andrew Wang 1C
Tue Oct 20, 2020 8:41 pm
Forum: Photoelectric Effect
Topic: Spectral Lines
Replies: 4
Views: 53

Re: Spectral Lines

Spectral lines represent the wavelength of the energy absorbed or emitted by an electron when it transitions from one energy level to another. The energy absorbed or emitted is equal to the difference in energy between the two levels that the electron transitions between, and you can use E=\frac{hc}...
by Andrew Wang 1C
Mon Oct 19, 2020 9:49 am
Forum: Properties of Light
Topic: How to quantify uncertainty
Replies: 2
Views: 20

Re: How to quantify uncertainty

The uncertainty of position or momentum is like standard deviation of either the position or momentum (velocity) of an object. For example, if an object's position was 3\pm2 m, then \Delta x would be equal to 4, as the object could be anywhere from 1 m to 5 m, and 5-1=4. Once you know the uncertaint...
by Andrew Wang 1C
Mon Oct 19, 2020 9:34 am
Forum: Properties of Light
Topic: photoelectric effect module help!!
Replies: 3
Views: 28

Re: photoelectric effect module help!!

The answer should be D. The photoelectric effect is one of the experiments that shows the particle properties of a photon. If photons acted only like waves, then increasing the intensity (amplitude) should result in ejected electrons (ike a wave at the beach, the higher it is, the stronger it is). H...
by Andrew Wang 1C
Thu Oct 15, 2020 10:05 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy gap
Replies: 4
Views: 39

Re: Energy gap

In addition to what Sid posted, the spectral lines in the UV region are part of the Lyman series, which has n1=1 for its lower energy level and n2=2 as its higher energy level, which is why they have higher energy and a shorter wavelength.
by Andrew Wang 1C
Wed Oct 14, 2020 10:33 pm
Forum: Properties of Light
Topic: Balmer vs Lyman
Replies: 12
Views: 108

Re: Balmer vs Lyman

A helpful way to identify when to use each series is to remember that the Balmer series occurs within the visible light range on the EM spectrum, so it'll have a longer wavelength and less energy, which makes sense since the energy difference is smaller between the higher levels and n=2 for the Balm...
by Andrew Wang 1C
Tue Oct 13, 2020 2:28 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Spectral Series
Replies: 2
Views: 33

Spectral Series

I was going over the solution to #15 in Focus 1A of the textbook, which said that each spectral series has its own lower energy level (Lyman is n=1, Balmer n=2, etc.). So this got me curious if each of the spectral series also corresponds with one region of the electromagnetic spectrum?
by Andrew Wang 1C
Mon Oct 12, 2020 11:06 am
Forum: Properties of Light
Topic: c=λv
Replies: 5
Views: 79

Re: c=λv

While it is true that c=λv describes the relationship betwen the wavelength and frequency of light, I don't think this equation allows you to figure out the exact graph. You would be able to conclude that the shape would be oscillatory however, since wavelength and frequency are both qualities of a ...
by Andrew Wang 1C
Mon Oct 12, 2020 10:59 am
Forum: Properties of Light
Topic: What exactly is Φ?
Replies: 16
Views: 153

Re: What exactly is Φ?

Φ is the amount of energy (unique to each element) that a photon needs to have for an electron to be ejected from a metal when it is hit with the proton. E = hv is the energy of a photon when it hits the metal (hv = Φ + E k ). So Φ would be equal to hv only if the electron is ejected with no excess ...
by Andrew Wang 1C
Thu Oct 08, 2020 11:45 pm
Forum: DeBroglie Equation
Topic: E = pc [ENDORSED]
Replies: 2
Views: 74

Re: E = pc [ENDORSED]

Hi there! E = pc is derived from E = mc 2 . Since c is the speed of light, we can think of E = mc 2 as E = mv 2 , or E = mvv. And since momentum p = mv, we can plug in momentum to get E = pv. After substituting c back in, we end up with E = pc. You can connect this with the equation from photoelectr...
by Andrew Wang 1C
Wed Oct 07, 2020 3:44 pm
Forum: Photoelectric Effect
Topic: Which one of following is not describing the photoelectric effect?
Replies: 3
Views: 42

Re: Which one of following is not describing the photoelectric effect?

I also thought it was E at first, but Arielle is correct that the answer is D. My reasoning was that although λv = c is used in photoelectric effect problems, it isn't specific to the photoelectric effect itself, while the other three equations are.

Hope this helps!
by Andrew Wang 1C
Tue Oct 06, 2020 2:23 pm
Forum: SI Units, Unit Conversions
Topic: Grams to Moles of Oxygen Gas
Replies: 7
Views: 50

Re: Grams to Moles of Oxygen Gas

Hi!
Since oxygen is one of the diatomic elements (along with Br, I, N, Cl, H, and F), it exists as O2. So when the question is talking about oxygen gas (O2), we should use 32.00 g/mol as a conversion factor.

Hope this helps!
by Andrew Wang 1C
Mon Oct 05, 2020 11:24 am
Forum: Balancing Chemical Reactions
Topic: Moles and Chemical Equations
Replies: 12
Views: 145

Re: Moles and Chemical Equations

Hi! The moles of each respective molecule is equal to the stoichiometric coefficient. The moles of each individual element in a molecule is equal to the stoichiometric coefficient times the subscript. So for your question, there would be 4 moles of hydrogen atoms, but 2 moles of water molecule. Hope...
by Andrew Wang 1C
Mon Oct 05, 2020 11:21 am
Forum: Balancing Chemical Reactions
Topic: Help Balancing this Equation, Problem L.35
Replies: 6
Views: 74

Re: Help Balancing this Equation, Problem L.35

Hey there! As the others have said, there's a typo for this problem. The third equation should actually read Fe3Br8 + Na2CO3 = NaBr + CO2 + Fe3O4, which is actually balanceable. If something like this comes up again, Dr. Lavelle has a page on the Chem 14A website that lists typos in our textbook, so...

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