Search found 94 matches
- Sun Mar 14, 2021 11:46 pm
- Forum: Student Social/Study Group
- Topic: How are y'all doing?
- Replies: 46
- Views: 2326
Re: How are y'all doing?
I was definitely less motivated this quarter than last quarter, but I was still able to make it through somehow. Hopefully next quarter I'll find an incentive to work harder.
- Sun Mar 14, 2021 8:38 pm
- Forum: Student Social/Study Group
- Topic: How to Reduce Nervousness before getting results
- Replies: 63
- Views: 4723
Re: How to Reduce Nervousness before getting results
Same as many other people here, I try to avoid thinking about it. There's no use in worrying about it if it's already past so you might as well make the most of your time before the results are actually out. I know it sounds a lot harder than I'm making it out to be, but as long as you're not consci...
- Sun Mar 14, 2021 8:34 pm
- Forum: Student Social/Study Group
- Topic: Spring Quarter
- Replies: 60
- Views: 2944
Re: Spring Quarter
I'm signed up for Chem 14BL! Hoping I'll have a little more free time next quarter.
- Sun Mar 14, 2021 8:32 pm
- Forum: Student Social/Study Group
- Topic: Distractions
- Replies: 15
- Views: 873
Re: Distractions
I am so sorry you have to go through this. I could only imagine having to live through this kind of situation first-hand. Don't feel ashamed because you have more important priorities than worrying about one grade or final. However, if it is of any consolation, just know that there are many other st...
- Sun Mar 07, 2021 11:37 pm
- Forum: Student Social/Study Group
- Topic: Book Recommendations
- Replies: 135
- Views: 11946
Re: Book Recommendations
The Picture of Dorian Gray by Oscar Wilde is a nice read if you’re into books that discuss morality and the such.
- Sun Mar 07, 2021 11:33 pm
- Forum: Student Social/Study Group
- Topic: Note Taking
- Replies: 145
- Views: 15076
Re: Note Taking
I’ll do a combination of note taking on Google docs and in my notebook. Most of the explanations and definitions go on docs, but when I need a more visual representation I’ll draw it out in my notebook.
- Sun Mar 07, 2021 10:24 pm
- Forum: Student Social/Study Group
- Topic: What do you miss / What are you looking forward to?
- Replies: 92
- Views: 8091
Re: What do you miss / What are you looking forward to?
I'm a bit of a social recluse, but I am looking forward to checking out some cool restaurants and cafes. There's a lot more cultural variety in LA than where I come from.
- Sun Mar 07, 2021 9:56 pm
- Forum: Student Social/Study Group
- Topic: Classes for next quarter?
- Replies: 165
- Views: 13036
Re: Classes for next quarter?
I'm taking Chem 14BL, Korean Civilization, and finishing my cluster in Interracial Dynamics!
- Sun Mar 07, 2021 8:13 pm
- Forum: Student Social/Study Group
- Topic: How do you deal with burnout?
- Replies: 144
- Views: 13090
Re: How do you deal with burnout?
I'm in the same boat, I've been burnt out for the majority of this quarter. Although I'm no expert, I typically try to stay focused by reserving a day or two specifically for work. I'll set up all my assignments and papers in bed and just focus on trying to reach a certain point, with snacks and a c...
- Sun Feb 28, 2021 11:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: tips if you're struggling!
- Replies: 77
- Views: 4386
Re: tips if you're struggling!
As someone who is also lazy and procrastinates a lot, these tips are really helpful! Thank you so much for suggestions.
- Sun Feb 28, 2021 11:27 pm
- Forum: Student Social/Study Group
- Topic: Chem 14B Final
- Replies: 86
- Views: 5083
Re: Chem 14B Final
From what I remember from 14A, the final is essentially the same as the midterm in terms of testing procedures. For studying, I would say that textbook problems and perhaps going over concepts discussed on sapling would be helpful for studying. Wish you luck on your final!
- Sun Feb 28, 2021 10:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling Week 7/9 #17
- Replies: 4
- Views: 233
Sapling Week 7/9 #17
Hi, I'm having a little trouble with 17. Could someone explain the steps they followed to get their answer.
What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions?
[H+] = 0.10 M PH2 = 3.8 atm T = 298 K
What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions?
[H+] = 0.10 M PH2 = 3.8 atm T = 298 K
- Sun Feb 28, 2021 9:51 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 #5
- Replies: 11
- Views: 2605
Re: Sapling Week 7/8 #5
Hi! This is how I solved for it. To balance half-reactions, I like to follow these steps: 1) Balance all of the elements except for H & O 2) To balance O: add water molecules 3) To balance H: add H+ ions 4) If the solution is basic, add the same number of OH- ions to BOTH sides as the number of...
- Sun Feb 28, 2021 9:19 pm
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 28594
Re: Fave food
Personally, I love most desserts that have cinnamon in them. I find myself craving churros, cinnamon rolls, and/or cinnamon cookies quite frequently.
- Sun Feb 28, 2021 8:59 pm
- Forum: Student Social/Study Group
- Topic: Moving to Westwood soon. Which restaurants should I visit?
- Replies: 45
- Views: 2493
Re: Moving to Westwood soon. Which restaurants should I visit?
Tsujita Ramen and Nong La are restaurants that I order from occasionally. I'm not sure about any boba places, but Junbi is a cool matcha themed joint if you're looking for some good drinks.
- Sun Feb 28, 2021 8:46 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 #5
- Replies: 11
- Views: 2605
Sapling Week 7/8 #5
I'm stuck on the 2nd part of question 5. I'm not sure whether it is due to a typing error or if my answer is genuinely wrong. Could someone share how they wrote it out? Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (...
- Sun Feb 21, 2021 9:10 pm
- Forum: Student Social/Study Group
- Topic: Classes for next quarter?
- Replies: 165
- Views: 13036
Re: Classes for next quarter?
I've currently enrolled for 14BL and the third quarter of my cluster. I think I'm planning on fulfilling a GE for my 3rd class.
- Sun Feb 21, 2021 8:44 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling #3 Week 7/8
- Replies: 1
- Views: 138
Sapling #3 Week 7/8
I'm a little lost on this one. Could someone explain how they got their answer?
- Sun Feb 14, 2021 11:58 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Intensive vs. Extensive Property
- Replies: 9
- Views: 463
Re: Intensive vs. Extensive Property
Extensive properties are dependent on the amount of matter (ex. mass, volume, weight, size, heat capacity, etc).
Intensive properties are not dependent on the amount of matter (temperature, density, color, solubility, specific heat capacity, etc).
Intensive properties are not dependent on the amount of matter (temperature, density, color, solubility, specific heat capacity, etc).
- Sun Feb 14, 2021 10:59 pm
- Forum: Student Social/Study Group
- Topic: Points needed to pass?
- Replies: 76
- Views: 6635
Re: Points needed to pass?
Considering you only need a 200/400 you could essentially get a 50% on all the tests and still pass with a 250/400. This assuming you get full credit for sapling and chemistry community requirements.
- Sun Feb 14, 2021 10:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: struggling
- Replies: 73
- Views: 3498
Re: struggling
I wouldn't say it's so much about doing all of the textbook problems as it is understanding them. If you can go through them confidently then that's a good indicator that you are doing well. If you don't have an underlying understanding for why something is when working out a problem, then I recomme...
- Sun Feb 14, 2021 10:19 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Can heat capacities be negative?
- Replies: 52
- Views: 13520
Re: Can heat capacities be negative?
Heat capacities can not be negative because it simply wouldn't make sense. It's similar to how you can't have a negative volume or negative distance. It's a system of measurement that measures how much heat is required to raise the temp by 1 C for a substance. Another way to look at it is that, if h...
- Sun Feb 14, 2021 12:01 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #7 Weeks 5/6
- Replies: 3
- Views: 153
Re: Sapling #7 Weeks 5/6
First you want to figure out how much of each substance was vaporized. To do this simply subtract the final mass from the initial mass of each substance. Once you have the mass of each substance you need to find how many moles there are of each substance. Second, you need to figure out how much ene...
- Sun Feb 14, 2021 11:20 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #7 Weeks 5/6
- Replies: 3
- Views: 153
Sapling #7 Weeks 5/6
Three liquid samples of known masses are heated to their boiling points with the use of a heater rated at 475.0 W. Once the boiling points of each sample are reached, the samples are heated for an additional 6.31 min, which results in the vaporization of some of each sample. After 6.31 min, the samp...
- Sun Feb 07, 2021 11:08 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #12 Week 3/4
- Replies: 5
- Views: 185
Re: Sapling #12 Week 3/4
First you would need to convert the given sample from grams to moles. Then you would multiply this value by the heat combustion given to get how many kJ were given off during the combustion (q). Keep in mind this value will need to be changed to be positive. Then you would use the equation q = (delt...
- Sun Feb 07, 2021 10:04 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling 3/4 #12 part b
- Replies: 3
- Views: 118
Re: Sapling 3/4 #12 part b
Yes, to calculate the heat of combustion you would multiply the value you got for C by the temperature change. Then you would divide this value by the given mass of the sample to get it in terms of per gram. The end value should be negative. Hopefully I explained this ok.
- Sun Feb 07, 2021 8:47 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #14 Week 3/4
- Replies: 7
- Views: 337
Sapling #14 Week 3/4
A sample of an ideal gas in a cylinder of volume 3.23 L at 298 K and 2.40 atm expands to 7.66 L by two different pathways. Path A is an isothermal, reversible expansion. Path B has two steps. In the first step, the gas is cooled at constant volume to 1.42 atm . In the second step, the gas is heated ...
- Sun Feb 07, 2021 8:03 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #12 Week 3/4
- Replies: 1
- Views: 102
Sapling #12 Week 3/4
I'm having a little trouble figuring out how to solve this problem? Can someone describe the process they followed? Suppose a 3.787 g sample of a second compound, compound B, is combusted in the same calorimeter, and the temperature rises from 25.13 ∘C to 30.66 ∘C. What is the heat of combustion per...
- Sun Feb 07, 2021 7:53 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling #8 Week3/4
- Replies: 6
- Views: 308
Re: Sapling #8 Week3/4
For this one I divided the amount of heat absorbed by the number of moles of CS2 produced from the reaction. In my example it was 358.8 kJ / 4 mol CS2 = 89.7. They asked how much can be produced from 381 kJ, so I then divided 381 by 89.7 to figure out how many moles of CS2 can be produced. 381 kJ / ...
- Sun Jan 31, 2021 11:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Making X negligible
- Replies: 34
- Views: 1302
Re: Making X negligible
I believe Lavelle said that if the K is less than 10^-4, then you can approximate. However, if you are not sure you can check by seeing if your final concentration is less than 5% of the initial concentration. If this is the case (<5%), then you can disregard having to use the quadratic formula.
- Sun Jan 31, 2021 11:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pka vs ka
- Replies: 28
- Views: 1255
Re: pka vs ka
When you deal with exponents, you know that when you divide or multiply values with exponents, you simply add or subtract them. (ex. 10^-14 / 10^-7 = 10^-7). The pKa takes the -log base 10 of the Ka value, so it's basically taking on the value of the exponent in a way. This is why you add when you d...
- Sun Jan 31, 2021 11:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy vs heat
- Replies: 31
- Views: 2219
Re: Enthalpy vs heat
Enthalpy can be described as the internal energy of the system. It is the amount of heat energy that is absorbed or given off during a chemical reaction at a constant pressure. Enthalpy is also a state function, meaning the change can be determined additively. Heat, on the other hand, is a form of e...
- Sun Jan 31, 2021 10:57 pm
- Forum: Phase Changes & Related Calculations
- Topic: Higher Enthalpy
- Replies: 6
- Views: 185
Higher Enthalpy
Just for clarification, if you heat a reaction that goes from a higher enthalpy to a lower enthalpy, the reaction will favor the reactants?
- Sun Jan 31, 2021 10:26 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Acids and Bases
- Replies: 15
- Views: 790
Acids and Bases
Does anyone know any resources or an easier way to determine what is a strong acid and what is a strong base? I still have trouble understanding this concept.
- Sun Jan 24, 2021 11:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sig Figs 5I.33
- Replies: 3
- Views: 161
Re: Sig Figs 5I.33
As far as I know from the midterms, Professor Lavelle has never had two options where the sig figs were the deciding factor. If your answer if close enough it should be fine. If you are really worried about this, just try to be as accurate as you can in your intermediate steps.
- Sun Jan 24, 2021 10:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Homework Week 2
- Replies: 5
- Views: 319
Re: Sapling Homework Week 2
When I was calculating #2, it said you have to use the quadratic formula to determine x because the percent ionization was greater than 5%. For all of the problems, (save for one I believe) you have to use the quadratic formula to determine the value of x.
- Sun Jan 24, 2021 10:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Neutral Solution
- Replies: 9
- Views: 690
Re: Neutral Solution
Since the Kw of pure water at 25 Celsius is 1 x 10^-14, the concentration of [H3O+] would have to be 1 x 10^-7 for it to be neutral. This would also mean that the concentration of [OH-] is 1 x 10^-7. If the concentration of hydronium ions [H3O+] is larger than hydroxide, that means that it would be ...
- Sun Jan 24, 2021 10:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb Formula
- Replies: 17
- Views: 579
Ka and Kb Formula
So when you're given Ka it says the formula is [H+][A-]/[HA]. In the video I watched it said you can simply write it as just x^2/[molarity - x] since [H+] and [A-] are equal. Is this statement always true?
- Sun Jan 24, 2021 7:59 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 2 Sapling #3
- Replies: 4
- Views: 265
Week 2 Sapling #3
Muscles produce lactic acid, CH3CH(OH)COOH(aq), during exercise. Calculate the percent ionization (deprotonation),pH, and pOH of a 0.1031 M solution of lactic acid. The acid‑dissociation (or ionization) constant, Ka, of this acid is 8.40×10−4. Percent Ionization = pH = pOH = So for this problem I fo...
- Mon Jan 18, 2021 12:01 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 1 Sapling #10
- Replies: 6
- Views: 167
Re: Week 1 Sapling #10
so basically what you would do to solve this is using the ICE box, your initial would now be 2.94 for NO2 and 0.335 for N2O4, then you would solve it like the usual ICE box problem you do using the equilibrium constant you found for the first problem. Afterward, you would use the smallest x you sol...
- Sun Jan 17, 2021 9:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 1 Sapling #10
- Replies: 6
- Views: 167
Week 1 Sapling #10
I'm having a little trouble with the last part of number 10. Could someone explain the steps they followed or how they calculated these values? The reaction: N2O4↽−−⇀2NO2 is allowed to reach equilibrium in a chloroform solution at 25 ∘C . The equilibrium concentrations are 0.335 mol/L N2O4 and 1.94 ...
- Sun Jan 17, 2021 9:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 #9
- Replies: 11
- Views: 737
Re: Sapling Week 1 #9
I am on my 9th attempt at this problem and I still am not sure what I am doing wrong. At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.200 M and [NO]=0.400 M. N2(g)+O2(g)↽−−⇀2NO(g) If more NO is added, bringing its concentration to 0.700 M, what will the final concentr...
- Sun Jan 17, 2021 8:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 1 Sapling #5
- Replies: 3
- Views: 103
Week 1 Sapling #5
Hi, so I've been having trouble with this problem, I thought I figured it out but it doesn't seem to be correct. Could someone please explain how to do this problem? Consider the reaction of NH3 and I2 to give N2 and HI. 2NH3(g)+3I2(g)↽−−⇀N2(g)+6HI(g)K Using two or more of the given equations, deter...
- Sun Jan 10, 2021 11:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Heterogenous Equilibriums
- Replies: 4
- Views: 182
Heterogenous Equilibriums
At the end of lecture 1, Professor Lavelle gives an example of solids and liquids in chemical equilibrium. E.g. Ca(OH)2(s) <--> Ca2+(aq) + 2OH-(aq) Kc = [Ca2+][OH-]2 He says that we only take into account aqueous solutions, and don't include solids and liquids when calculating equilibrium because th...
- Sun Jan 10, 2021 11:28 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K Favors Products or Reactants
- Replies: 20
- Views: 571
Re: K Favors Products or Reactants
Using the equation Kc = [P]/[R], we can determine whether the products or reactants are favored. If the numerator (concentration of products) is greater than the denominator (concentration of reactants), the value of K will be greater than 1. If it were the other way around and the denominator were ...
- Sun Jan 10, 2021 11:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 53
- Views: 1919
Re: K vs. Q
Yes Q and K are essentially the same thing. The only difference is that K is the concentration of products and reactants when it is at equilibrium and Q is at any time during the reaction. Q's value relative to K can be used to determine the direction that the reaction is tending towards.
- Sun Jan 10, 2021 10:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Stoichiometric Coefficients
- Replies: 5
- Views: 106
Re: Stoichiometric Coefficients
From what I've found on the internet, it appears this is based on how to equation was formed in the first place based on how the calculation is defined. It has something to do with finding the point at which delta G equals 0. However, if you just think about it logically, when the reactions back an...
- Sun Jan 10, 2021 10:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Stoichiometric Coefficients
- Replies: 5
- Views: 106
Stoichiometric Coefficients
I'm not sure if it was explicitly mentioned, but why is it that the stoichiometric coefficients become the exponents when calculating the equilibrium constant?
- Sun Jan 10, 2021 9:34 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K relationship
- Replies: 12
- Views: 522
Re: Q and K relationship
Basically my TA described that K is the optimal concentration of products and reactants, as opposed to Q where it is just the amount of products and reactants at any given time. The reaction is always going to want to head towards K. So if Q is greater than K, the reaction going to want to go left t...
- Sun Dec 06, 2020 11:59 pm
- Forum: Resonance Structures
- Topic: Resonance Structures and Stability
- Replies: 4
- Views: 283
Resonance Structures and Stability
I'm a little confused about resonance structures and their corresponding stabilities. If I'm correct, a resonance structures exist because one Lewis structure can't fully describe the structure of a molecule. Are all resonance structures equivalent if that is the case? If not, why is that?
- Sun Dec 06, 2020 11:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorizing Molecular Geometry
- Replies: 6
- Views: 150
Memorizing Molecular Geometry
My TA said that we should probably memorize the VSEPR models up until the steric number 6 for the final. Did anyone else hear something different or do you think this is adequate?
- Sun Dec 06, 2020 10:55 pm
- Forum: Octet Exceptions
- Topic: Clarification on Expanded Octets
- Replies: 3
- Views: 239
Clarification on Expanded Octets
Can someone expand on what having an expanded octet means? I know it has to do with utilizing the d-subshell, and therefore the bonding atom can have more than 8 valence electrons. However I'm still slightly confused about how many valence electrons each atom (with an expanded octet) can have?
- Sun Dec 06, 2020 10:20 pm
- Forum: Significant Figures
- Topic: When should I start looking at sig figs?
- Replies: 31
- Views: 1385
Re: When should I start looking at sig figs?
It's best to save the rounding til the end, and use as many decimal spaces as possible in your calculations. This way your final value will be the closest to the actual value and you can adjust the sig figs accordingly.
- Sun Dec 06, 2020 9:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity
- Replies: 7
- Views: 204
Polarity
Asking for clarification. So a molecule with polar bonds can still be non-polar (following that the molecular structure is symmetrical and other factors), while a molecule with a polar molecular structure will always be considered polar?
- Sun Nov 29, 2020 11:37 pm
- Forum: Empirical & Molecular Formulas
- Topic: Periodic Table and Calculations
- Replies: 21
- Views: 1493
Re: Periodic Table and Calculations
I have a TI-84, it's a pretty good calculator for longer calculations. Also I would recommend using the periodic table he has posted on the chem 14A website, you can't go wrong there.
- Sun Nov 29, 2020 11:27 pm
- Forum: Significant Figures
- Topic: 40. versus 40
- Replies: 23
- Views: 1514
Re: 40. versus 40
Yes, because the decimal in 40. denotes that the 0 adds to the precision. Because of the lack of decimal in 40, we are unsure if the 0 is precise or not.
- Sun Nov 29, 2020 11:24 pm
- Forum: Resonance Structures
- Topic: Resonance
- Replies: 11
- Views: 631
Re: Resonance
When a molecule has different resonance structures, the only thing that changes is the arrangement of electrons (structure of atoms, # of lone pairs, and overall formal charge remains the same). However, some resonance structures are more stable because the formal charges of the individual atoms are...
- Sun Nov 29, 2020 10:51 pm
- Forum: Significant Figures
- Topic: Sig Figs
- Replies: 12
- Views: 516
Re: Sig Figs
In a question, the measured value with the least amount of sig figs will determine how many sig figs your answer should be. Generally when doing numerous consecutive calculations, it's good to use as many digits as you can and wait until the last step to round. This way your answer is the most accur...
- Sun Nov 29, 2020 10:25 pm
- Forum: SI Units, Unit Conversions
- Topic: How to memorize prefixes
- Replies: 36
- Views: 3447
Re: How to memorize prefixes
Before when I wasn't as confident with them, I would try to think of other words with the prefixes to help me (ex. decathlon, cent, millennium). If you can't come up with any, or if you have trouble memorizing them, I'm sure there are several mnemonics online that can make it easier.
- Sun Nov 22, 2020 11:48 pm
- Forum: Significant Figures
- Topic: Sig Fig Question
- Replies: 12
- Views: 922
Re: Sig Fig Question
Yes, the decimal was used to indicate that the measurement was precise up to that point, and that the 0 should be considered a significant figure.
- Sun Nov 22, 2020 11:47 pm
- Forum: SI Units, Unit Conversions
- Topic: unit conversions
- Replies: 24
- Views: 1147
Re: unit conversions
I don't really see another way to do it, besides writing out the full values and multiplying them, but that wouldn't be efficient. I would definitely say to just keep it in scientific notation when performing your calculations.
- Sun Nov 22, 2020 11:06 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Ionic Bond and Covalent Character
- Replies: 4
- Views: 290
Ionic Bond and Covalent Character
Would a bond between a cation with a high charge density and an anion with low ionization create an ionic bond with the most covalent character, or is it based off other factors as well?
- Sun Nov 22, 2020 10:56 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic and Covalent Bonds
- Replies: 7
- Views: 427
Ionic and Covalent Bonds
I know that atoms in an ionic bond have a larger difference in electronegativity than those in a polar covalent bond, but is there another way to distinguish between the two?
- Sun Nov 22, 2020 10:39 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Optimal Formal Charge Configuration
- Replies: 3
- Views: 224
Optimal Formal Charge Configuration
My friend showed me a question that asked which thiocyanate structure was the most stable based off formal charge (written as [SCN]-). There were two options listed, one where the Sulfur had the -1 charge and one where the Nitrogen was given the -1 charge. In this case, would it be more stable for t...
- Sun Nov 15, 2020 11:59 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Sapling #9 week 5/6
- Replies: 13
- Views: 664
Re: Sapling #9 week 5/6
From what I read, the formal charges of the individual atoms is important to determining which model is the most plausible. In the answers that were correct, they had only one atom that had a non-zero formal charge. For example one model had a Cl(-1) and another had O(-1), with the rest of the atoms...
- Sun Nov 15, 2020 11:41 pm
- Forum: SI Units, Unit Conversions
- Topic: picometer conversion
- Replies: 13
- Views: 1761
Re: picometer conversion
Yeah, you would just divide the value (in this case 1.5 x 10^-10) by the unit conversion for picometers (1 x 10^-12) and you would get 150. You can calculate it quickly by seeing that there is a 10^2 difference between the 10's and simply moving the decimal place 2 times to the right.
- Sun Nov 15, 2020 11:29 pm
- Forum: SI Units, Unit Conversions
- Topic: Memorizing SI Units
- Replies: 14
- Views: 2462
Re: Memorizing SI Units
I'd say that it's probably good to have the most common units memorized. For example kilo (10^3), milli (10^-3), micro (10^-6), nano (10^-9), and pico (10^-12) are the ones most often used.
- Sun Nov 15, 2020 11:21 pm
- Forum: Lewis Structures
- Topic: Hydrogen Bonding
- Replies: 12
- Views: 508
Hydrogen Bonding
On a few of the Sapling questions, it mentioned that hydrogen bonding can not occur when the hydrogen atom is bonded to a carbon atom. It can only occur when hydrogen is bonded to either oxygen, fluorine, or nitrogen. I think he went over this in one of his lectures, but I'm still not entirely sure ...
- Sun Nov 15, 2020 11:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling #9
- Replies: 1
- Views: 65
Sapling #9
I'm a little confused about #9 on Sapling. The resonance hybrid of the perchlorate ion, ClO4- is described by 16 resonance structures, a representative subset of which is shown. Which of the Lewis Structures of the perchlorate ion are most plausible based on formal charge? I eventually got the answe...
- Sun Nov 08, 2020 11:19 pm
- Forum: Significant Figures
- Topic: 0's
- Replies: 32
- Views: 1287
Re: 0's
Yes, the decimal signifies that the 0's are part of a precise measurement, that is, they had a tool of measurement that could measure accurately to that extent. Without the decimal point, we don't whether it's actually accurate or if it was simply rounded for conveniency.
- Sun Nov 08, 2020 11:09 pm
- Forum: Trends in The Periodic Table
- Topic: Electron-Electron Repulsion
- Replies: 2
- Views: 86
Electron-Electron Repulsion
I know that electron-electron repulsion results in a slightly larger atomic radius, but between what electrons does this repulsion occur (those in the same energy level, subshell, or orbital)?
- Sun Nov 08, 2020 10:39 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Subshell Energies
- Replies: 6
- Views: 264
Subshell Energies
I'm a little confused on the energy of the different subshells. I'm not sure if I remember this correctly, but I think in one of his lectures he said that in some cases, the subshells have the same energy, and in other cases, some of the subshells have higher energy. What changed for this to happen?
- Sun Nov 08, 2020 10:00 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Effective Nuclear Charge
- Replies: 2
- Views: 146
Effective Nuclear Charge
I know that as you go across a period in the periodic table, the effective nuclear charge increases, and as a result, the atomic radius decreases. However, exactly is happening to cause an increase in the effective nuclear charge?
- Sun Nov 08, 2020 8:58 pm
- Forum: Properties of Light
- Topic: Study Advice
- Replies: 50
- Views: 2080
Re: Study Advice
Personally, I would say to do a little bit of everything. When I was studying for the midterm I took a couple days to quickly scan the textbook and its examples, doing a few of the problems for each concept. Then I did Sapling and watched some of the modules and I'd say my understanding was pretty g...
- Sun Nov 01, 2020 10:27 pm
- Forum: Einstein Equation
- Topic: Sapling #1
- Replies: 6
- Views: 1216
Re: Sapling #1
Yes, when you have 100 photons with the same wavelength and frequency (wavelength and frequency are inversely proportional), then the only thing that would change would be the intensity (amplitude) of the EM radiation. This also affects the amount of energy. The wavelength/frequency are specific to ...
- Sun Nov 01, 2020 9:50 pm
- Forum: Properties of Electrons
- Topic: Rydberg's Equation
- Replies: 6
- Views: 312
Re: Rydberg's Equation
Thank you guys for the clarification. I've also seen variants of the equation in which the R that is factored out is sometimes negative and sometimes positive. Is this because they are reversing the order of n1 and n2?
- Sun Nov 01, 2020 8:49 pm
- Forum: Properties of Electrons
- Topic: Rydberg's Equation
- Replies: 6
- Views: 312
Rydberg's Equation
Hi, I'm slightly confused with which value corresponds with which variable for Rydberg's formula. Initially, (when it comes to emission) I thought n1(initial) stood for the higher shell and n2(final) stood for the lower shell. But I've seen some examples where it's the other way around. So are n1 an...
- Sun Nov 01, 2020 8:04 pm
- Forum: Properties of Light
- Topic: Is c always the speed of light?
- Replies: 92
- Views: 4928
Re: Is c always the speed of light?
Like what everyone else is saying, c is a variable specific to the speed of light. If velocity were supposed to be another value, it would typically be expressed with the variable (v).
- Sun Nov 01, 2020 7:48 pm
- Forum: Properties of Light
- Topic: Week 2 Homework Sapling #7
- Replies: 5
- Views: 256
Re: Week 2 Homework Sapling #7
First you would need to calculate the energy of a photon with that wavelength. You would use the equation E(proton)= hc/λ (which is derived from the equation E=hv). So in this case it would be E= (6.626 x 10^-34 Js) x (3x10^8m/s)/(769 x 10^-9). E= 2.5849 x 10^19 This is the energy per one photon. If...
- Sun Oct 25, 2020 10:38 pm
- Forum: Significant Figures
- Topic: Midterm
- Replies: 9
- Views: 506
Re: Midterm
Not really sure where I heard this (maybe at one of the workshops?) , but I remember someone saying that sometimes there are questions where the only difference is the sig figs. Not saying it's going to be on the midterm though, but even so, I heard partial credit would be given if that was your onl...
- Sun Oct 25, 2020 8:28 pm
- Forum: Properties of Light
- Topic: Light spectrum
- Replies: 8
- Views: 258
Re: Light spectrum
From what my TA said, we should memorize the order of the EM spectrum and the general wavelengths that correspond with the type of radiation (my TA specified that we should know the wavelengths for visible light). I'm not sure about the frequency though.
- Sun Oct 25, 2020 8:20 pm
- Forum: Significant Figures
- Topic: Sig Figs and Zeroes
- Replies: 5
- Views: 528
Re: Sig Figs and Zeroes
Basically, the only zeroes that matter are the ones contributing to the actual precision of the measurement. For example, to put it into practice, if you were to have 5 grams of a substance, you can see that there is only one sig fig. If you were to convert that to kilograms you would have .005 kg. ...
- Sun Oct 25, 2020 8:02 pm
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 21116
Re: How to relax
I like to just lay in bed and relax. Maybe watch some videos or listen to some calming music. I have been trying to exercise more tho :).
- Sun Oct 25, 2020 7:48 pm
- Forum: Student Social/Study Group
- Topic: Advice for Midterm Studying?
- Replies: 7
- Views: 319
Advice for Midterm Studying?
What have you guys found is the most useful in terms of studying for the midterm (reading the textbook, using the modules, sapling, etc.)? I'm aware it'd be best to do all of them, but I'm just speaking in terms of what I should prioritize first, or what has worked best for you.
- Sun Oct 18, 2020 9:21 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Module Question #24
- Replies: 3
- Views: 130
Re: Photoelectric Effect Module Question #24
Typically, the photoelectric effect experiment is conducted using UV light. However, this will sometimes differ based on the threshold frequency of the metal surfaces. Some metal surfaces require higher frequencies to emit an electron, and others can emit an electron with lower frequencies. But yeah...
- Sun Oct 18, 2020 8:26 pm
- Forum: Properties of Light
- Topic: Kinetic Energy of Electron
- Replies: 4
- Views: 190
Re: Kinetic Energy of Electron
Chanel Mao 2F wrote:Hi!
I'm not sure if this is what you meant, but you can also calculate the kinetic energy of an electron when you subtract the work function from the energy of the photon. Hope this helped!
Thank you! That's basically all I wanted to know.
- Sun Oct 18, 2020 8:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Respondus
- Replies: 4
- Views: 138
Respondus
In my discussion section we didn't go over how to use Respondus. I was wondering, besides downloading the app and getting a webcam, is there anything else we're expected to do before the exam. Or is it pretty self explanatory?
- Sun Oct 18, 2020 7:48 pm
- Forum: Properties of Light
- Topic: Kinetic Energy of Electron
- Replies: 4
- Views: 190
Kinetic Energy of Electron
So to calculate the kinetic energy of an emitted electron you would use the equation E(k) = 1/2mv^2. I was just wondering if there was any other way to derive the kinetic energy from other values given in the or would using this equation be the only way?
- Sun Oct 18, 2020 7:11 pm
- Forum: Properties of Light
- Topic: Work Function
- Replies: 3
- Views: 191
Work Function
I'm a little confused about the work functions that were used during the lectures/modules on the photoelectric effect. Is it just a quantity that defines the threshold value for emitting an electron? How would you solve for it and/or what would you solve for using the work function?
- Sun Oct 11, 2020 8:41 pm
- Forum: Balancing Chemical Reactions
- Topic: Order of Balancing Rxns
- Replies: 23
- Views: 616
Re: Order of Balancing Rxns
Personally, I start by balancing the element that is least common (or elements that only appear in one molecule) so you can get a foundation, and leave the more common and isolated elements for last (i.e. O2). This makes it much easier to make adjustments in the end that won't affect the entirety of...
- Sun Oct 11, 2020 8:16 pm
- Forum: SI Units, Unit Conversions
- Topic: Correct Units for Chem Problems
- Replies: 3
- Views: 101
Re: Correct Units for Chem Problems
Yes, you should determine the units of your answer based on the question. Typically, the question will directly or indirectly specify which unit the answer should preferably be in. Otherwise, like the above posts said, Prof. Lavelle did state in one of the lectures that Celsius is more commonly used...
- Sun Oct 11, 2020 7:48 pm
- Forum: Significant Figures
- Topic: Scientific Notation
- Replies: 4
- Views: 136
Re: Scientific Notation
Just a little tip for writing in scientific notation. Don't forget to include your sig figs (sometimes when they are 0's it can be confusing). For example, if writing out .00200 in scientific notation, you would include the 0's trailing after 2 because they are significant figures. So it would be wr...
- Sun Oct 11, 2020 7:30 pm
- Forum: Significant Figures
- Topic: Sapling #4
- Replies: 10
- Views: 569
Re: Sapling #4
Yes Adam, the 0's proceeding the decimal would count because it is adding to the precision of the measurement. The decimal almost acts as a point of clarification, letting us know that the 0's are intentional (rather than a result of rounding or conveniency). For example, with the number 2000, we do...
- Sun Oct 11, 2020 1:32 pm
- Forum: Significant Figures
- Topic: Sig Fig for numbers like 200, 3300, 4000
- Replies: 6
- Views: 314
Re: Sig Fig for numbers like 200, 3300, 4000
I'm not sure if this will help clarify the answer for you, but the reason 200 only has 1 sig fig is because the 0's after the 2 aren't contributing to the precision of the measurement (or at least we don't know if they are, it's too ambiguous). For example, the number 200 could've been chosen out of...