Search found 142 matches

by Eugene Chung 3F
Thu Oct 10, 2019 10:29 pm
Forum: Properties of Light
Topic: Electromagnetic Spectrum
Replies: 4
Views: 67

Re: Electromagnetic Spectrum

It does not mention that in the class website "Learning outcome; Outline 2: The Quantum World" pdf, but some HW questions requires that knowledge.
by Eugene Chung 3F
Thu Oct 10, 2019 10:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Where do we check our grades?
Replies: 3
Views: 92

Re: Where do we check our grades?

I think we get all the homework and tests back with the grading on each of it. As for the final grade, I also believe that we just have to wait out until the final grade is out on myucla.
by Eugene Chung 3F
Thu Oct 10, 2019 10:21 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percentage Question
Replies: 9
Views: 491

Re: Mass Percentage Question

add the molar masses (the mass shown in the periodic table) for each element in the compound. than, divide each element by the total molar mass of the compound.
by Eugene Chung 3F
Thu Oct 10, 2019 10:19 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 Grading
Replies: 12
Views: 457

Re: Test 1 Grading

I'm pretty sure it is graded on how many points out of 50 we get on the test. But if not, I think the test is out of 40 points and we get 10 points for being there? I heard from my friend who took chem 14a last year that her test was out of 40 points.
by Eugene Chung 3F
Thu Oct 10, 2019 10:17 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M Homework Problem M.11
Replies: 3
Views: 258

Re: Fundamentals M Homework Problem M.11

you can use other ways to find out what the limiting reactant is. I think we use o2 to do so since to solve the next part of the question, you have to calculate how much excess o2 you get.
by Eugene Chung 3F
Thu Oct 10, 2019 10:13 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Unit for Avogadro's Number
Replies: 10
Views: 410

Re: Unit for Avogadro's Number

if the question asks how many atoms, then it would be atoms. If the question asks how many molecules/ formula units, then it's molecules/formula unit. It can also be used for protons, etc.
by Eugene Chung 3F
Fri Oct 04, 2019 7:09 pm
Forum: Properties of Light
Topic: Amplitude
Replies: 6
Views: 150

Re: Amplitude

I believe amplitude is independent of both regarding EM since the speed is fixed.
by Eugene Chung 3F
Fri Oct 04, 2019 7:06 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution post assessment problem 25
Replies: 1
Views: 64

Dilution post assessment problem 25

I struggled solving this problem and ended up solving it using the volume ratios. I wanted to know if there was any other way to solve this problem.
Anyone willing to share tips of dilution problems?
by Eugene Chung 3F
Fri Oct 04, 2019 6:56 pm
Forum: Administrative Questions and Class Announcements
Topic: using older edition textbook
Replies: 8
Views: 138

Re: using older edition textbook

All the hw problems so far pretty much matched up with the 6th edition!
by Eugene Chung 3F
Tue Oct 01, 2019 11:30 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant Lecture Question
Replies: 5
Views: 173

Re: Limiting Reactant Lecture Question

I believe that it is highly unlikely to have no limiting reactant (and of course no excess) realistically. Since we base our moles using the Avogadro number, which is only approximately 6.022x10^23, it is almost impossible to weight out precisely one mole of something accurately (to 23 decimals) in ...
by Eugene Chung 3F
Tue Oct 01, 2019 11:21 pm
Forum: Administrative Questions and Class Announcements
Topic: using older edition textbook
Replies: 8
Views: 138

using older edition textbook

Is it okay to use an older edition textbook instead of the 7th?
Specifically, I have the 5th edition and was wondering if the questions and material would be drastically different from the 7th edition one.
by Eugene Chung 3F
Sun Sep 29, 2019 4:20 pm
Forum: Limiting Reactant Calculations
Topic: Determining mass of product produced based on limiting reagent
Replies: 2
Views: 52

Determining mass of product produced based on limiting reagent

[img]
19839186-3BD9-43E4-8B62-13173E7ECFC5.jpeg
[/img]

I’m not sure how to determine the mass of HCl in this problem
I have balanced the equation (3 in front of water and hydrogen chloride)
by Eugene Chung 3F
Sun May 27, 2018 11:21 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Ionisation [ENDORSED]
Replies: 2
Views: 394

Re: Ionisation [ENDORSED]

A strong acid will completely ionize in water while a weak acid will only partially ionize.
by Eugene Chung 3F
Sun May 27, 2018 11:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Drawing
Replies: 7
Views: 468

Re: VSEPR Drawing

I'm pretty sure in the lecture professor lavelle told us that he would not ask us to draw the shapes on the tests because it is hard to grade.
by Eugene Chung 3F
Sun May 27, 2018 11:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angle
Replies: 9
Views: 440

Re: Bond angle

Bond angle is affected by the presence of lone pair of electrons at the central atom. A lone pair of electrons at the central atom always tries to repel the shared pair (bonded pair) of electrons. Due to this, the bonds are displaced slightly inside resulting in a decrease of bond angle
by Eugene Chung 3F
Sun May 27, 2018 11:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shapes within the P orbital [ENDORSED]
Replies: 3
Views: 514

Re: Shapes within the P orbital [ENDORSED]

Here's a visual representation of the answers. Image
by Eugene Chung 3F
Sun May 27, 2018 11:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Any Other Shapes?
Replies: 7
Views: 518

Re: Any Other Shapes?

Image
by Eugene Chung 3F
Sun May 27, 2018 11:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs and polarity
Replies: 2
Views: 212

Re: lone pairs and polarity

Larger molecules, even if they have only one kind of atom, are sometimes polar. This will occur when the central atom has one or more pairs of nonbonded electrons. One example of this is ozone, O3. The middle oxygen atom has a lone pair of electrons and this lone pair gives the molecule its polarity.
by Eugene Chung 3F
Sun May 20, 2018 4:43 pm
Forum: Ionic & Covalent Bonds
Topic: Configurations
Replies: 4
Views: 263

Re: Configurations

make sure to switch d and s when writing configurations. But also, it is important to remember that 4s fills up first.
by Eugene Chung 3F
Wed May 16, 2018 11:13 am
Forum: Determining Molecular Shape (VSEPR)
Topic: How to determine molecular shape
Replies: 5
Views: 336

Re: How to determine molecular shape

I think we have to refer to VSEPR notation/ molecular geometry for that, which we have not learned yet in this class.
by Eugene Chung 3F
Wed May 16, 2018 11:11 am
Forum: Ionic & Covalent Bonds
Topic: Electron affinity [ENDORSED]
Replies: 6
Views: 380

Re: Electron affinity [ENDORSED]

noble gases are exception for electron affinity because since their outermost energy levels are completely filled with electrons, therefore, another electron cannot enter that level. This means that noble gases have basically zero electron affinity and highest ionization energies.
by Eugene Chung 3F
Wed May 16, 2018 11:07 am
Forum: Ionic & Covalent Bonds
Topic: Naming Molecules
Replies: 5
Views: 226

Re: Naming Molecules

i believe we just have to know ch 3 (more specifically #5, 9(a,b), 11(a,b), 13, 19(omit part c), 21, 23, 25, 27, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51,53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 93, 95, 97, 99, 101, 103, 117, 119, 121, 123 ) for the test.
by Eugene Chung 3F
Wed May 16, 2018 11:02 am
Forum: Ionic & Covalent Bonds
Topic: Percentage Ionic Character
Replies: 4
Views: 328

Re: Percentage Ionic Character

the guideline states that if electronegativity difference is greater than 2, it is ionic bond
by Eugene Chung 3F
Wed May 16, 2018 11:00 am
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 5
Views: 357

Re: Electronegativity

I learned in highschool that
0.0-0.2 nonpolar covalent
0.3-1.4 polar covalent
>1.5 ionic
but that might be different for this class!
by Eugene Chung 3F
Wed May 16, 2018 10:58 am
Forum: Resonance Structures
Topic: Coordinate covalent bond
Replies: 2
Views: 181

Coordinate covalent bond

In last friday's lecture, Professor Lavelle taught us about the coordinate covalent bond with BF4- as one example. Does having a coordinate covalent bond imply that you also have acid base reaction?
by Eugene Chung 3F
Sun May 06, 2018 1:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: configuration for silver [ENDORSED]
Replies: 1
Views: 146

configuration for silver [ENDORSED]

I wrote 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^10, 4s^2, 4p^6, 4d^9, 5s^2 since we fill s orbital first and then fill d orbital then we switch those two. But the solution says 4d^10, 5s^1.

WHICH IS CORRECT?
by Eugene Chung 3F
Sun May 06, 2018 12:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What is Zeff (prob 2.37) [ENDORSED]
Replies: 2
Views: 205

Re: What is Zeff (prob 2.37) [ENDORSED]

Zeff is effective nucleus charge and is affected by the total number of electrons present in an atom because the electrons in the lower energy orbitals will shield the electrons in the higher energy orbitals from the nucleus.This is because the electrons repelling each other tends to counteract the ...
by Eugene Chung 3F
Sun May 06, 2018 12:42 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Question about HW#2.37
Replies: 1
Views: 177

Question about HW#2.37

2.37 Which of the following statements are true for many- electron atoms? If false, explain why. (a) The effective nuclear charge Zeff is independent of the number of electrons present in an atom. (b) Electrons in an s-orbital are more effective than those in other orbitals at shielding other electr...
by Eugene Chung 3F
Thu Apr 26, 2018 6:57 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Constant [ENDORSED]
Replies: 6
Views: 442

Re: Rydberg Constant [ENDORSED]

I believe we're using 3.29 x 10^15 Hz
by Eugene Chung 3F
Wed Apr 25, 2018 6:22 pm
Forum: Properties of Electrons
Topic: Question about n and energy levels
Replies: 3
Views: 279

Question about n and energy levels

does n basically mean energy level?
by Eugene Chung 3F
Sun Apr 22, 2018 3:17 pm
Forum: Properties of Light
Topic: Speed of Light which is more accurate? [ENDORSED]
Replies: 6
Views: 1550

Re: Speed of Light which is more accurate? [ENDORSED]

I believe that all the constants we need to know will be provided for HW, tests, etc... So I think it will be best to just use whatever is given. However, 299 792 458 m / s is more accurate.
by Eugene Chung 3F
Sun Apr 22, 2018 3:13 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Baseball through sensors experiment [ENDORSED]
Replies: 5
Views: 369

Re: Baseball through sensors experiment [ENDORSED]

I've read online that motion detectors are small electronic eyes that detect infrared waves—heat waves that radiate from moving objects. When the detector senses an object moving across its field of view—especially warmer objects such as people, animals and cars—it electronically turns on the lights...
by Eugene Chung 3F
Sun Apr 22, 2018 3:11 pm
Forum: Properties of Light
Topic: Question About Photons [ENDORSED]
Replies: 3
Views: 230

Question About Photons [ENDORSED]

How can photons have momentum if it doesn't have mass?
by Eugene Chung 3F
Sun Apr 22, 2018 3:09 pm
Forum: *Black Body Radiation
Topic: Black Body Radiation [ENDORSED]
Replies: 5
Views: 1233

Re: Black Body Radiation [ENDORSED]

It is normally defined as any physical body absorbs and emits electromagnetic radiation when its temperature is above absolute zero.
by Eugene Chung 3F
Sun Apr 22, 2018 3:07 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Equation
Replies: 7
Views: 721

Re: Balancing Equation

The matrix method helped me a lot in balancing equations!
Image
by Eugene Chung 3F
Sun Apr 22, 2018 3:05 pm
Forum: Einstein Equation
Topic: 1.26 Question
Replies: 1
Views: 237

1.26 Question

1.26 When an electron beam strikes a block of copper, x-rays with a frequency of 1.2 1017 Hz are emitted. How much energy is emitted at this wavelength by (a) an excited copper atom when it generates an x-ray photon; (b) 2.00 mol of excited copper atoms; (c) 2.00 g of copper atoms? so far I've done ...
by Eugene Chung 3F
Sun Apr 22, 2018 3:02 pm
Forum: Properties of Electrons
Topic: Question 1.49
Replies: 1
Views: 204

Question 1.49

1.49 The energy levels of a particle of mass m in a two-dimensional square box of side L are given by
(n12 n22)h2/8mL2. Do any of these levels have the same energy? If so, nd the values of the quantum numbers n1 and n2 for the rst three cases.
by Eugene Chung 3F
Sun Apr 22, 2018 3:01 pm
Forum: *Black Body Radiation
Topic: Homework Question 1.30
Replies: 1
Views: 432

Homework Question 1.30

1.30 The very hot star Spica has a surface temperature of
23 kK (2.3 104 K). At what wavelength does Spica emit the maximum intensity of light?

How do I find the maximum intensity of light?
by Eugene Chung 3F
Sun Apr 22, 2018 2:59 pm
Forum: *Black Body Radiation
Topic: Question 1.21
Replies: 5
Views: 679

Question 1.21

1.21 From the following list of observations, select the one that best supports the idea that electromagnetic radiation has the properties of particles. Explain your reasoning.
(a) Black-body radiation.
(b) Electron diffraction.
(c) Atomic spectra.
(d) The photoelectric effect.
by Eugene Chung 3F
Sun Apr 22, 2018 2:50 pm
Forum: Limiting Reactant Calculations
Topic: Question M8
Replies: 3
Views: 391

Question M8

M.8 The antiperspirant aluminum chloride is made by reacting solid aluminum oxide, solid carbon, and chlorine gas. Carbon monoxide gas is also produced in the reaction. (a) Write a balanced equation for the reaction. (b) What mass of aluminum chloride can be produced when 185 kg of aluminum oxide is...

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