Search found 117 matches
- Sun Mar 14, 2021 8:31 pm
- Forum: Student Social/Study Group
- Topic: Spring Quarter
- Replies: 60
- Views: 3290
Re: Spring Quarter
I'm taking 14C in the spring quarter! I wanted to also enroll in 14BL but it was filled up :(
- Sun Mar 14, 2021 8:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Equilibrium constant
- Replies: 2
- Views: 303
Re: Equilibrium constant
Your equation for finding Kc is the concentration of the products/concentration of reactants, with each raised to an exponent equal to their corresponding coefficients in the reaction. For example: H2(g) + Br2(g) <--> 2 HBr(g) Kc = [HBr]^2 /[H2][Br2] *Remember that solids and liquids aren't included...
- Fri Mar 12, 2021 11:38 am
- Forum: Student Social/Study Group
- Topic: Planning on dorming in the Fall?
- Replies: 61
- Views: 3442
Re: Planning on dorming in the Fall?
I plan on dorming in the fall! I'd prefer dorms, but if they don't give an offer due to limited capacity, I'll probably get an apartment. :)
- Fri Mar 12, 2021 11:22 am
- Forum: General Rate Laws
- Topic: Sapling 9&10 #7
- Replies: 10
- Views: 901
Re: Sapling 9&10 #7
#Part 5: The generic rate law is: rate=k [A]^a [B]^b [C]^c k is the rate constant. [A], [B], and [C] are the initial concentrations of the reactants. a, b, and c are the orders of the reactants (A, B, and C). You found the order of the reactant A in part 1: 1st order --> a = 1 You found the order o...
- Fri Mar 12, 2021 11:07 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy and reaction rate
- Replies: 2
- Views: 197
Re: Activation Energy and reaction rate
In order for the reaction to proceed, it must pass the transition state. To pass the transition state, the energy needed for the reaction to proceed is known as the activation energy. Activation energy can be thought of as a hindrance to reaction progress. A higher activation energy results in a slo...
- Fri Mar 12, 2021 11:02 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Lowering Activation Energy
- Replies: 34
- Views: 1221
Re: Lowering Activation Energy
Yes, a catalyst lowers the activation energy in the reverse reaction as well as the forward reaction. A catalyst increases the rate of both the forward and reverse reactions by providing an alternate path of lower activation energy in either direction.
- Fri Mar 12, 2021 10:54 am
- Forum: Administrative Questions and Class Announcements
- Topic: Solutions Manual
- Replies: 4
- Views: 386
Re: Solutions Manual
Here's the solutions: Atkins_7e_SSM_Fundamentals_1-7_9.pdf There are some errors in the solution manual so make sure to refer to the file on the class website that lists the errors --> Here's a link to it: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Solution_Manual_Errors_7Ed.p...
- Fri Mar 05, 2021 9:29 pm
- Forum: Student Social/Study Group
- Topic: Review Sessions
- Replies: 11
- Views: 1025
Re: Review Sessions
If you aren't able to attend some of the sessions, the worksheets from some sessions are usually posted on Chemistry Community, so look out for those too!
- Fri Mar 05, 2021 9:22 pm
- Forum: Calculating Work of Expansion
- Topic: Work sign
- Replies: 46
- Views: 2078
Re: Work sign
It depends on which way the work is done. If work is done ON the system, then work would be POSITIVE. If work is being done BY the system, then work would be NEGATIVE since the system is exerting energy onto the surroundings by doing the work. Compression of a system usually means work is being done...
- Fri Mar 05, 2021 9:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Studying for Final
- Replies: 17
- Views: 837
Re: Studying for Final
For textbook problems, I'm planning to focus on the more complicated problems from each section. I personally struggled the most on thermodynamics, so I may try to watch more videos from organic chemistry tutor to gain a better understanding and maybe even do some of the basic textbook problems to b...
- Fri Mar 05, 2021 8:49 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Sapling Week 9/10 #13
- Replies: 2
- Views: 206
Re: Sapling Week 9/10 #13
You base the rate law on the rate-determining step, which is usually the slowest step. In this case, it is I−(aq) + HClO(aq) → HIO(aq) + Cl−(aq) The rate law for the slowest step would be rate = k [HClO][I−] You also need to note how HClO is an intermediate, so you need to substitute [HClO] with th...
- Fri Mar 05, 2021 8:12 am
- Forum: General Rate Laws
- Topic: Concentration Denotation
- Replies: 7
- Views: 443
Re: Concentration Denotation
Yes, brackets are mostly used to indicate concentrations.
- Sun Feb 28, 2021 5:59 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling #5 wk7/8
- Replies: 2
- Views: 193
Re: Sapling #5 wk7/8
You balanced it right, but I think it's because your (-) for 2OH- and 2ClO2- is after the phase indication. I would put them as 2OH-(aq) and 2ClO2-(aq) instead of 2OH(aq)- and 2ClO2(aq)-
- Sun Feb 28, 2021 5:45 pm
- Forum: Balancing Redox Reactions
- Topic: sapling #19
- Replies: 6
- Views: 414
Re: sapling #19
You balanced it right! Don't put the parenthesis... I did that too and Sapling kept marking me wrong :) It should be: 4Fe+3O2+6H2O⟶2Fe2O3∙3H2O Fe2O3•H2O indicates that it contains water. Any chemical compound that has the dot followed by water indicates that it is a hydrate, which means that it's a ...
- Sat Feb 27, 2021 7:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B final date and time?
- Replies: 9
- Views: 573
Re: 14B final date and time?
The final is on Sunday, March 14 from 9:30 am – 11:00 am. Unlike the midterms, there aren't separate times for different lectures, but you join your TA proctoring link just like the previous times. I think the only alternative time is for international students from 7:00 am – 8:30 am.
- Sat Feb 27, 2021 7:06 pm
- Forum: Student Social/Study Group
- Topic: Final
- Replies: 63
- Views: 3523
Re: Final
I would go over the sections you struggled with the most. Since the test questions are similar to the textbook ones, it's good to redo those exercises too. I recommend organic chemistry tutor on Youtube if you want some explanations on topics.
- Sat Feb 27, 2021 10:44 am
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 39047
Re: Fave food
I just made banana bread today! My most favorite food is Thai food (spicy basil fried rice and pad kee mao) all-day everyday. Favorite dessert would be cinnamon rolls :)
- Sun Feb 21, 2021 1:57 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling #2
- Replies: 7
- Views: 395
Re: Sapling #2
You need to balance the half-reactions and then add them together to get your overall reaction: First balance the charges in the half‑reactions by adding electrons: In⟶In3+ + 3e− Cd2+ + 2e− ⟶ Cd Then, balance the # of e- transferred in each half-reaction so that it is the same in both half-reactions...
- Sun Feb 21, 2021 1:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: summer session classes
- Replies: 17
- Views: 938
Re: summer session classes
I'm not really sure, but they may update the professors closer to the summer session. I would advise signing up soon though since most classes seem to be filling up, if they haven't already.
- Sun Feb 21, 2021 12:30 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: STP (standard temperature and pressure)
- Replies: 8
- Views: 3822
Re: STP (standard temperature and pressure)
STP indicates 0 degrees Celcius and 1 atm pressure.
- Sun Feb 21, 2021 12:28 pm
- Forum: Student Social/Study Group
- Topic: Post Midterm 2 De-stressing
- Replies: 92
- Views: 7133
Re: Post Midterm 2 De-stressing
I binge-read the Lunar Chronicles series!
- Sun Feb 21, 2021 12:06 pm
- Forum: General Science Questions
- Topic: MT 2 grades
- Replies: 34
- Views: 1950
Re: MT 2 grades
I haven't gotten an email about when it would be released, but I would expect it to generally take a week.
- Sun Feb 14, 2021 6:03 pm
- Forum: Van't Hoff Equation
- Topic: Sapling #18
- Replies: 12
- Views: 712
Re: Sapling #18
First isolate ln(K) to one side. Then, to get K, you should do e^(whatever is on the other side).
Here's an example of how to do it with some random numbers:
ln(x) = 2.3/4
x = e^(2.3/4)
Here's an example of how to do it with some random numbers:
ln(x) = 2.3/4
x = e^(2.3/4)
- Sun Feb 14, 2021 2:05 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Weeks 5/6 #19
- Replies: 6
- Views: 369
Re: Sapling Weeks 5/6 #19
I used the same equation: ΔG=ΔG∘+RTln(Q) ΔG∘ = −69.0 kJ/mol and T = 298 K as given in the problem. We first need to calculate Q. Q=(PNO2)^2/(PO2)(PNO)^2=(0.650)^2/(0.250)(0.450)^2= 8.35 Since they want the final answer of ΔG in kJ/mole, make sure all your units are correct . In this case, the R valu...
- Sun Feb 14, 2021 1:48 pm
- Forum: Student Social/Study Group
- Topic: Fav Shows of the Moment
- Replies: 115
- Views: 47420
Re: Fav Shows of the Moment
I'm currently watching WandaVision. I wasn't into it at first, but it's picking up and dropping a bunch of interesting storylines, so I'm waiting to see where it goes :). I'm also rewatching Cutthroat Kitchen in my downtime. Waiting for Grey's Anatomy to come back in March!
- Sun Feb 14, 2021 1:40 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Sapling week 5/6 #3
- Replies: 12
- Views: 2907
Re: Sapling week 5/6 #3
Yes, you are right! The entropy of a material increases with an increase in the number of microstates. Entropy decreases when going from a freely moving state to one of limited movement where there are fewer possible arrangements of molecules, such as gas to solid. Enthalpy increases as a substance ...
- Sun Feb 14, 2021 1:05 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff equation mistake?
- Replies: 6
- Views: 480
Re: Van't Hoff equation mistake?
The two equations seem to be the same. In the equation from the lecture, a (-1) was factored out and put it in front of the rest of the equation. This allowed rearranging of the equation to make 1/T2 positive. In the equation from the textbook, you can see that they didn't factor out a negative, so ...
- Sun Feb 14, 2021 12:58 pm
- Forum: Student Social/Study Group
- Topic: Classes for next quarter?
- Replies: 165
- Views: 15729
Re: Classes for next quarter?
I'm planning to take Chem14C, 14BL, LS7B, and Cluster 48CW seminar. I hope I can get my ideal times before they fill up :)
- Sun Feb 07, 2021 10:19 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling 3/4 #12 part b
- Replies: 3
- Views: 138
Re: Sapling 3/4 #12 part b
YES! To calculate the heat of combustion for compound B, qB, multiply the constant C you found earlier by the temperature change: qB=C ×(Tf−Ti) *Since heat is being released, the qB value is supposed to be negative The question asks for the heat of combustion per gram of compound B, so divide qB by ...
- Sun Feb 07, 2021 2:23 pm
- Forum: Student Social/Study Group
- Topic: Studying When You Don't Want to
- Replies: 48
- Views: 2751
Re: Studying When You Don't Want to
The best thing that helped me was to make a list and schedule out what I would do throughout the day. Breaking up tasks into smaller parts and spreading them throughout the day made it easier for me to accomplish the stuff that I dreaded the most. I start off with a task that I am more motivated to ...
- Sun Feb 07, 2021 12:52 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling Question #9 Week 3/4
- Replies: 3
- Views: 609
Re: Sapling Question #9 Week 3/4
The heat gained by the cold water is equal to the heat lost by the hot water according to the equation: m (cold water) CΔT (cold water) =−m (hot water) CΔT (hot water) Convert the volume of water to grams using the density conversion of 1.00 g/mL --> The mass of cold ...
- Sun Feb 07, 2021 12:26 pm
- Forum: Student Social/Study Group
- Topic: Students Who Have a Job
- Replies: 103
- Views: 10019
Re: Students Who Have a Job
I work part-time at Kumon, but luckily my job is currently over Zoom working with kids. Whenever there is downtime between my sessions, I tend to spend that time getting the simpler class assignments finished, such as article reading. This helps me get ahead in my daily schedule. It's definitely dif...
- Sun Feb 07, 2021 12:18 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Sapling Week 5/6 #19
- Replies: 2
- Views: 617
Re: Sapling Week 5/6 #19
You would be using this equation: ΔG = ΔG° + RT*ln(Q) Since you know the partial pressures, you can plug those into the K expression to get Q --> Q = (Pnh3)^2 / ((Pn2)*(Ph2)^3) = (0.600)^2 / (0.500 * (0.200^3))=90 ΔG° is already given: -69.0 kJ/mol R = 8.314 J/mol*K but you want it to be in kJ/mol*K...
- Sun Jan 31, 2021 11:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Relationship between pka and conjugate base
- Replies: 2
- Views: 196
Re: Relationship between pka and conjugate base
If the conjugate base is strong, it means that pKa would be higher for the weaker acid it comes from (small Ka value for the weak acid).
- Sun Jan 31, 2021 7:40 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Reset?
- Replies: 17
- Views: 1476
Re: Sapling Reset?
Since there are unlimited attempts, I'm assuming you can just re-attempt the questions. I'm not sure you can reset the problems though.
- Sun Jan 31, 2021 7:39 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm #1 Results
- Replies: 18
- Views: 905
Re: Midterm #1 Results
He hasn't sent out anything yet, but it usually took about a week for the scores to be released. It might be similar this quarter too.
- Sun Jan 31, 2021 7:36 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14C?
- Replies: 23
- Views: 974
Re: 14C?
I plan to take 14C along with 14BL in the spring. This just mostly because it is a long series and I prefer not to take a gap in the series.
- Sun Jan 31, 2021 7:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: Sapling week 3/4 #4
- Replies: 9
- Views: 1413
Re: Sapling week 3/4 #4
In endothermic reactions , the energy required to break the reactant bonds is more than the energy released during the formation of product bonds. To see which one is endothermic, it should be the reactions that have stronger bonds for the reactants than the product bonds. For example: AB+C⟶AC+B Bas...
- Sun Jan 24, 2021 5:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3 #6
- Replies: 5
- Views: 253
Re: Sapling Week 3 #6
Enthalpy can be thought of as ΔH∘rxn= (bond energy of bonds broken) - (bond energy of bonds formed) For CH4(g)⟶C(g)+4H(g), 4 C−H bonds are broken without the formation of any other bonds. 4-0 = 4. This means that ΔH∘rxn could be equal to 4×bond energy of C−H. C(g)+4H(g)⟶CH4(g) is the reverse reactio...
- Sun Jan 24, 2021 4:58 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Textbook Problems Not Listed in Syllabus
- Replies: 3
- Views: 275
Re: Textbook Problems Not Listed in Syllabus
I mostly focus on the problems listed on the syllabus, since they seem the most relevant. But, I'm sure the other problems not mentioned can give you more practice if you want to.
- Sun Jan 24, 2021 4:47 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH sig figs
- Replies: 4
- Views: 366
Re: pH sig figs
It is based on what's after the decimal when given a pH value. So, in this case, there are 3 sig figs.
- Sun Jan 24, 2021 4:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to find the H+ from pH
- Replies: 12
- Views: 523
Re: How to find the H+ from pH
To find the pH, you do: pH = -log[H+]
When you know the pH, you can reverse it to find [H+] by doing 10^(-pH).
Example:
5.6 = -log[H+] ---> [H+] = 10^-5.6 = 2.5 x 10^-6
When you know the pH, you can reverse it to find [H+] by doing 10^(-pH).
Example:
5.6 = -log[H+] ---> [H+] = 10^-5.6 = 2.5 x 10^-6
- Sun Jan 24, 2021 4:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: [B]formal
- Replies: 5
- Views: 353
Re: [B]formal
Bformal is the formal concentration of B, the amine. You find this by adding the [BH+] and [B].
Bformal = [BH+] + [B]
Bformal = [BH+] + [B]
- Sun Jan 24, 2021 4:21 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: sapling week 2 #5
- Replies: 15
- Views: 540
Re: sapling week 2 #5
Yes, so far that's the correct value for x! You are going to use the Kb expression to evaluate the value of [B] by setting the expression equal to the Kb value and also plugging in your known concentrations (in this case, the products). In the expression, the x value you found earlier is what you pu...
- Sun Jan 17, 2021 6:15 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Post Assessment Question 17 Part 4
- Replies: 4
- Views: 392
Re: Post Assessment Question 17 Part 4
When it is endothermic, heat is on the reactants side. When it is exothermic, heat is released, so heat is on the products side. So, increasing temperature has an effect depending on if it is an exothermic or endothermic reaction. Increasing the temperature for endothermic reactions shifts the equil...
- Sun Jan 17, 2021 6:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: sapling number 9
- Replies: 3
- Views: 175
Re: sapling number 9
The error was in your numbers once you expanded your expression. When you expanded the squared expressions, it should be: 4(0.09 + 0.6x + x^2) = 0.81 - 3.6x + 4x^2 0.36 + 2.4x + 4x^2 = 0.81 - 3.6x + 4x^2 0.36 + 2.4x = 0.81 - 3.6x 6x = 0.45 x = 0.075 When you plug that x value into 0.9 - 2x, you shou...
- Sun Jan 17, 2021 5:53 pm
- Forum: Student Social/Study Group
- Topic: Comfort Movies
- Replies: 168
- Views: 26329
Re: Comfort Movies
I love the Princess Diaries! My go-to movie is Shrek, but I also love to re-watch episodes of Spongebob and The Fairly OddParents for fun.
- Sun Jan 17, 2021 5:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 and 2 #9
- Replies: 5
- Views: 256
Re: Sapling Week 1 and 2 #9
So far, you're correct. You have (0.8-2x)^2/(0.1+x)^2 = 25. Take the square root of both sides and solve for x. Once you get the value of x, plug it into 0.8-2x to get the final [NO]
- Sat Jan 16, 2021 3:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week One #9
- Replies: 2
- Views: 142
Re: Sapling Week One #9
First, I solved for the Kc value by plugging in the concentrations given in the beginning. (0.4^2)/(0.3)(0.3), which gave the Kc value as 1.778. When you do the ice table, your equilibrium values for the reactants should be (0.3 + x) and for the product is (0.7 - 2x). Plug these into the Kc expressi...
- Sat Jan 16, 2021 3:04 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Textbook Question 6D.3
- Replies: 3
- Views: 214
Re: Textbook Question 6D.3
I don't think you made an error, but it was probably due to sig figs. They did each step with 1 sig fig. So instead of 6.3E-2 for [H3O+] and [Cl2-], their value was 0.06 or 6E-2. This made a difference in the rest of the calculations, which were also within 1 sig fig.
- Sat Jan 16, 2021 2:53 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook Problem 5.61
- Replies: 2
- Views: 183
Re: Textbook Problem 5.61
6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g) Liquids don't impact equilibrium. Also, pressure relates to gases, so aqueous solutions wouldn't be considered for this scenario. When you focus on the gases, you see that there is an equal amount of moles of gas on both sides. Thus, there would no net impact...
- Sun Jan 10, 2021 1:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook problem 5J.5
- Replies: 3
- Views: 185
Re: Textbook problem 5J.5
Pressure and Volume are inversely related. The smaller the volume, the higher the pressure. When the total pressure is increased, the side with less moles is favored. For example, part (a) is 2 moles of gas on the reactants and 3 moles of gas on the products. Since there is a greater amount of moles...
- Sun Jan 10, 2021 1:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Example from lecture
- Replies: 3
- Views: 190
Re: Example from lecture
It comes from the Kc expression. They multiplied the denominator onto the other side. That leaves you with x^2=1.80 (3.00-X). Distribute the 1.80 and you get the expression as x^2= 5.40 - 1.80x. Then, you get all the terms onto one side: x^2 + 1.80x - 5.40. Hope this helps!
- Sat Jan 09, 2021 6:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 #4
- Replies: 4
- Views: 177
Re: Sapling Week 1 #4
Sophia Kalanski 1A wrote:ok but how do you figure out x from here?
Plug the expressions from the E section of the Ice table into the Kp expression (products/reactants). You know the Kp value, so set that Kp expression equal to that value. Solve for x.
- Sat Jan 09, 2021 5:55 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Problem 5I.13
- Replies: 2
- Views: 141
Re: Textbook Problem 5I.13
You need to use an ICE table. You know the Kc value from Table 5G.2. Plug all the expressions from the ICE table into the Kc expression and set it equal to the value from Table 5G.2. Using the quadratic formula, solve for x. Knowing this x value, you will be able to evaluate the concentrations at eq...
- Thu Jan 07, 2021 11:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium Part 1A Post-Module Assessment
- Replies: 2
- Views: 221
Re: Chemical Equilibrium Part 1A Post-Module Assessment
The ratio of initial concentrations refers to products/reactants and their values are what the initial concentrations are when the reaction starts. The ratio of equilibrium concentrations is also products/reactants but the values are measured when the reaction reaches equilibrium. The equilibrium co...
- Wed Dec 16, 2020 3:45 pm
- Forum: Student Social/Study Group
- Topic: Winter Break
- Replies: 44
- Views: 2281
Re: Winter Break
I'm personally going to take this winter break to relax, especially after a tough quarter. However, I will read over my notes again closer to the beginning of the winter quarter. It might also help to review the textbook problems if you want more practice review.
- Thu Dec 10, 2020 7:21 pm
- Forum: Bronsted Acids & Bases
- Topic: Sapling Week 10 #2
- Replies: 7
- Views: 576
Re: Sapling Week 10 #2
A Bronsted acid can donate H+, so there should be a Hydrogen in the formula. A Bronsted base can accept H+, which can be indicated by a negative charge as it allows the substance to accept an H+. If it meets both descriptions, it can be amphoteric.
- Thu Dec 10, 2020 6:55 pm
- Forum: Limiting Reactant Calculations
- Topic: Textbook Question M.9
- Replies: 1
- Views: 200
Re: Textbook Question M.9
Spectator ions don't take part in the chemical reaction to form a precipitate. By looking at the product, you can differ which are the spectator ions. For example, Cu(NO3)2 + NaOH --> Cu(OH)2. In this equation, you can see that Na^+ and NO3^- are not involved in creating the final product of the pre...
- Thu Dec 10, 2020 1:51 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Bidentate Question
- Replies: 1
- Views: 55
Re: Bidentate Question
The oxygens have different formal charges, impacting whether they can bind to something else. Two of the oxygen atoms have a formal charge of zero and don't bind to more electrons. The other two oxygens (with the double bonds) have a formal charge of -2. These two have the ability to make bonds. Sin...
- Thu Dec 10, 2020 12:50 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Textbook 6C.17
- Replies: 1
- Views: 131
Re: Textbook 6C.17
BrO- is the conjugate base of a weak acid (HBrO). The conjugate base of a weak acid is usually relatively strong. Based on the structure, C17H19O3N has a nitrogen with a lone pair of electrons and presents as a weak base. Since BrO- is relatively strong and morphine is weak, BrO- is the stronger base.
- Tue Dec 08, 2020 6:35 pm
- Forum: Significant Figures
- Topic: Things to remember for final?
- Replies: 20
- Views: 1317
Re: Things to remember for final?
Ok so I understand we should memorize the strong acids/bases but which ones are they... The ones he mentioned in Week 9 Wed. Lecture? I believe these are the strong bases he mentioned (Li2O,NaOH,Na2O,KOH,CaO,Ca(OH2),Mg(OH)2) .. but I cannot find the strong acids. can someone list them? thank you! T...
- Tue Dec 08, 2020 6:24 pm
- Forum: Dipole Moments
- Topic: induced dipole
- Replies: 6
- Views: 448
Re: induced dipole
A dipole refers to a molecule with opposite charges on both ends. Dipoles tend to be for polar molecules. Induced dipoles are temporary. When an ion or molecule with a dipole comes near a molecule without a true dipole, it will induce the distortion of that molecule's electron cloud, making it have ...
- Sun Dec 06, 2020 5:33 pm
- Forum: Amphoteric Compounds
- Topic: Sapling HW #2 [ENDORSED]
- Replies: 4
- Views: 675
Re: Sapling HW #2 [ENDORSED]
A Bronsted acid can donate H+, so there should be a Hydrogen in the formula. This leaves H3PO4, HBrO2, H2PO4^- to be possible answers. A Bronsted base can accept H+, which can be indicated by a negative charge as it allows the substance to accept an H+. Out of the 3 possible answers, H2PO4^- has a n...
- Sun Dec 06, 2020 5:26 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Sapling #10. How can you tell which solution has a higher pH?
- Replies: 7
- Views: 2002
Re: Sapling #10. How can you tell which solution has a higher pH?
Those with higher ph are bases. The strong bases have a higher pH than weaker bases. The weaker bases have higher pH than acids. The strong acids have the lowest pH values. It would be helpful to recognize the strong acids and the strong bases first before you place the weaker acids and bases in ord...
- Sat Dec 05, 2020 8:29 pm
- Forum: Student Social/Study Group
- Topic: Sapling learning
- Replies: 4
- Views: 404
Re: Sapling learning
The website we use is sapling learning. Here is the link: https://www.saplinglearning.com/ibiscms/login/
- Sat Dec 05, 2020 7:59 pm
- Forum: Bronsted Acids & Bases
- Topic: Do acids always list hydrogens as the first element in a molecule?
- Replies: 3
- Views: 181
Re: Do acids always list hydrogens as the first element in a molecule?
One example of an exception I found when doing the week 10 sapling hw was Acetic Acid. It is a weak acid and its formula is CH3COOH.
- Sat Dec 05, 2020 7:48 pm
- Forum: Bronsted Acids & Bases
- Topic: Relative strength of acids and bases
- Replies: 2
- Views: 150
Re: Relative strength of acids and bases
So Ka is the acid dissociation constant. That's why the larger it is the more likely it is a strong acid, since strong acids completely dissociate into ions. Ka is essentially the [products]/[reactants]. The [A-] is the concentration of the conjugate base. The [H+] is the concentration of the hydrog...
- Sun Nov 29, 2020 9:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling #20
- Replies: 6
- Views: 456
Re: Sapling #20
I'm not sure if your problem is different but mine was asking to draw AsO4^3-. If that is the same as yours, I put As in the middle and the 4 O's around it. I did one double bond between 1 oxygen and the As. The rest of the bonds between the oxygens and As are single bonds. Then, I just put lone pai...
- Sun Nov 29, 2020 8:52 pm
- Forum: Hybridization
- Topic: hybridization, but very simple
- Replies: 9
- Views: 624
Re: hybridization, but very simple
Yes! For hybridization, you count the regions of electron density. So, single bonds, double bonds, and triple bonds all count as 1 region of electron density (the type of bond doesn't affect the number of regions of electron density). 5 regions of electron density should be a hybridization of sp3d.
- Sun Nov 29, 2020 5:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Weekly Discussion grades
- Replies: 9
- Views: 369
Re: Weekly Discussion grades
I don't think so. According to the syllabus, the only things that are worth points are sapling, chemistry community, the 2 midterms, and the final.305311217 wrote:So do we not get credit for attending section?
- Sat Nov 28, 2020 8:11 pm
- Forum: Lewis Acids & Bases
- Topic: question 17 sapling
- Replies: 7
- Views: 384
Re: question 17 sapling
One structure is the linear structure with a triple bond between two of the carbons. Another structure is with double bonds between the carbons. The third structure is a triangular ring of the carbons with 2 carbons double bonded to each other. In this molecule, those two carbons are also bonded to ...
- Sat Nov 28, 2020 8:03 pm
- Forum: Hybridization
- Topic: Multiple Bonds with Hybridization
- Replies: 6
- Views: 342
Re: Multiple Bonds with Hybridization
When determining hybridization, you count the regions of electron density, not the type of bond. Single, double, or triple bonds between atoms count as one region of electron density. That's why there wouldn't be a different hybridization for a molecule with 4 single bonds and a molecule with 3 sing...
- Sat Nov 28, 2020 7:49 pm
- Forum: Lewis Structures
- Topic: sapling #17 week 7&8
- Replies: 5
- Views: 292
Re: sapling #17 week 7&8
The structure is cyclopropene, with the 3 carbons in a triangular three-membered ring. There's a double bond between two of the carbons. Those same two carbons are also single bonded to 1 hydrogen each. The 3rd carbon atom is bonded to 2 hydrogens. I did my structure like this:
- Sat Nov 28, 2020 7:39 pm
- Forum: Lewis Structures
- Topic: SnCl2 lewis structure
- Replies: 2
- Views: 651
Re: SnCl2 lewis structure
The total number of electrons in the molecule is 4 + 7(2), which is 18. You would place Sn in the middle and a Cl atom on each side of it. I usually start by placing a single bond between the atoms. Then I fill the octet of the Cl atoms. I then put the remaining electrons on Sn, having 2 electrons a...
- Fri Nov 27, 2020 1:10 pm
- Forum: Student Social/Study Group
- Topic: Winter 2021 Classes
- Replies: 20
- Views: 1061
Re: Winter 2021 Classes
Thank you! Also, would it be okay to take the Chem 14BL Lab section from 11am-1:30pm on Friday even though it goes into Chem 14B's friday lecture at 1pm, since the lecture is recorded? I would avoid overlap with the lecture time because Professor Lavelle said in an email that tests are during lectu...
- Fri Nov 27, 2020 12:42 pm
- Forum: Student Social/Study Group
- Topic: Final Exam Tips
- Replies: 24
- Views: 1039
Re: Final Exam Tips
I tend to review my notes I wrote again and then watch Organic Chemistry Tutor videos on topics I need more insight on. For the final exam, I'm focusing on understanding the new material first. Then, I'm going through my notes from previous units. After reviewing all my notes, I also redo the Textbo...
- Fri Nov 27, 2020 12:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: sigma bonds and single bonds
- Replies: 5
- Views: 293
Re: sigma bonds and single bonds
Double bonds consist of one sigma and one pi bond. Single, double, and triple bonds all have one sigma bond and the remaining within that bond are pi bonds. So, for single bonds, it's only one sigma bond. Triple bonds have one sigma and two pi bonds.
- Thu Nov 19, 2020 9:00 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 3d and 4s
- Replies: 9
- Views: 605
Re: 3d and 4s
Most of the textbook answers seemed to do this for electron configurations. I think they used the electrons in the 4s orbital to get a half-filled or full d-orbital when possible since those are the most stable.
- Thu Nov 19, 2020 8:54 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Charge of a Molecule / Distribution of Charge
- Replies: 5
- Views: 382
Re: Charge of a Molecule / Distribution of Charge
You can use formal charge to find the charge of the ion, since if you add all the formal charges, it will give you the molecule's overall charge.
- Thu Nov 19, 2020 8:22 pm
- Forum: *Shrodinger Equation
- Topic: SE importance
- Replies: 4
- Views: 443
Re: SE importance
Shrodinger's equation is essentially a math function where when you square psi you get electron density. Electron density meaning the probability of finding an electron Adding on, the probability of finding an electron varies depending on the orbital, since there may or may not have nodal planes(ar...
- Thu Nov 19, 2020 8:16 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Multiple Posts under a topic
- Replies: 1
- Views: 112
Re: Multiple Posts under a topic
Under my posts, they're just grouped by forum, so you won't see each post you made on the same forum. However, when you're in a forum, under your name it shows the number of posts you've made. If you click on that number, it shows all of the comments, even the ones on the same forum. So, I think you...
- Thu Nov 19, 2020 8:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Rules of ionization energy
- Replies: 18
- Views: 1774
Re: Rules of ionization energy
Ionization energy increases across a period because there is a higher effective nuclear charge, so the electrons are held more tightly, and thus requires more energy to remove an electron. Ionization energy also decreases down a group, since the outer electrons are farther from the nucleus and are h...
- Thu Nov 19, 2020 7:52 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polar Covalent Bond
- Replies: 8
- Views: 337
Re: Polar Covalent Bond
How do you find the differences in the electronegativities? Is it based on where they are on the periodic table? Since we probably won't get the values of electronegativities of the elements for the midterm, you can use the periodic table as a measure. Electronegativity increases up and to the righ...
- Sun Nov 15, 2020 12:18 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1d number 15
- Replies: 2
- Views: 93
Re: 1d number 15
Thorium is another exception. In this case, the energy level 6d is lower than 5f, so it will be filled first. You probably don't need to focus much on this element since it isn't one of the exceptions we should know for this class.
- Sun Nov 15, 2020 12:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem 14B and 14BL
- Replies: 3
- Views: 94
Re: Chem 14B and 14BL
It's mostly up to you. Some decide to take it sequentially so that they will have learned the material and have a basis before taking 14BL. If you think you want to take them together, you can!
- Sun Nov 15, 2020 11:54 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Clarification on Oxidation Numbers
- Replies: 2
- Views: 236
Re: Clarification on Oxidation Numbers
For formal charge, electrons are assigned assuming that they are equally shared without concern for which atom is most electronegative. On the other hand, oxidation numbers assign electrons to the most electronegative atom in the bond.
- Sun Nov 15, 2020 12:47 am
- Forum: Student Social/Study Group
- Topic: grade worries
- Replies: 119
- Views: 19469
Re: grade worries
At least for this Midterm 2, the questions are worth fewer points each unlike Midterm 1. We just need to try our best by preparing and understanding the material as well as we can!
- Fri Nov 13, 2020 6:56 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lecture Content for 11/13
- Replies: 3
- Views: 201
Re: Lecture Content for 11/13
No, it should be up until Wednesday's lecture.
- Fri Nov 13, 2020 6:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture #18
- Replies: 3
- Views: 144
Re: Lecture #18
Yes, the midterm covers material up to Wednesday's lecture. It covers the last 8 points of the Quantum World (Outline 2) and Outline 3.
- Thu Nov 05, 2020 8:39 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polyatomics ions
- Replies: 4
- Views: 173
Re: Polyatomics ions
Polyatomic ions are just ions composed of multiple atoms. The atoms in polyatomic ions are held together by covalent bonds. It is only ionic when a polyatomic ion bonds with a metal. The elements in NH4 are nonmetals because they possess the properties of nonmetals. Also, they are under the nonmetal...
- Thu Nov 05, 2020 2:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Points to Grades Breakdown
- Replies: 5
- Views: 270
Re: Points to Grades Breakdown
The grade breakdown isn't available on his syllabus. But, if it is similar to other classes, I assume 90% is an A- (450/500).
- Wed Nov 04, 2020 5:43 pm
- Forum: Lewis Structures
- Topic: Electron count for cations and anions
- Replies: 1
- Views: 89
Re: Electron count for cations and anions
Yes! You are correct in your calculations. Anions gain electrons and become negatively charged since they have more electrons than protons. So, you do add an electron (or more depending on the charge of the anion). Cations lose electrons as they become more positively charged. So for protons, you su...
- Wed Nov 04, 2020 5:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Fall 2020 Midterm 1 Instructions
- Replies: 20
- Views: 1931
Re: Fall 2020 Midterm 1 Instructions
David He wrote:When will the score released, and where can we see them?
Dr. Lavelle sent an email earlier today that said Midterm scores should be updated by tomorrow(Thursday) midday. You can check on CCLE once they are available.
- Wed Nov 04, 2020 5:29 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Participation Points [ENDORSED]
- Replies: 62
- Views: 3644
Re: Participation Points [ENDORSED]
I'm not sure if this question got answered earlier in the thread, but do posts have to be strictly chem related (like asking or answering a lecture question) to earn points, or would a post like this one count towards the weekly total? Since it's participation points, I don't think it has to be str...
- Wed Oct 28, 2020 7:56 pm
- Forum: Properties of Light
- Topic: Do we need to know the ranges of waves on the electromagnetic spectrum?
- Replies: 7
- Views: 264
Re: Do we need to know the ranges of waves on the electromagnetic spectrum?
I think it's good to know the general range of wavelengths for visible light and UV since it's in our notes. Knowing the general trend of increasing wavelength sizes might help for the rest of the light spectrum (which are shorter and which are longer).
Here's an EM Spectrum that might help!
Here's an EM Spectrum that might help!
- Wed Oct 28, 2020 6:18 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: The Quantum World Outline
- Replies: 3
- Views: 212
Re: The Quantum World Outline
In regards to molecular spectroscopy, it is more complex because it is composed of multiple atoms and will have a unique spectra (unlike in atomic spectroscopy which deals with one atom). When electrons transition in a molecule, there will be more spectral lines because each individual atom in the m...
- Wed Oct 28, 2020 6:07 pm
- Forum: Limiting Reactant Calculations
- Topic: Cl vs Cl2
- Replies: 9
- Views: 7329
Re: Cl vs Cl2
Yes, Cl2 is the correct way if it says chlorine gas. Oxygen would also be O2. This is because these elements exist as diatomic molecules.
- Wed Oct 28, 2020 6:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Audio-Visual Focus Topics
- Replies: 14
- Views: 485
Re: Audio-Visual Focus Topics
I agree that they helped a lot to better understand topics with more practice examples especially when studying! Unfortunately, I think the ones posted are it. There doesn't seem to be any mention of more audio-visual focus topics in other outlines.
- Wed Oct 28, 2020 5:56 pm
- Forum: Trends in The Periodic Table
- Topic: Trends in Groups 15 and 16
- Replies: 4
- Views: 287
Re: Trends in Groups 15 and 16
As a trend, yes. Group 15 elements generally have lower ionization energy than group 16 elements.