## Search found 67 matches

Sun Jan 24, 2021 6:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5G.11
Replies: 2
Views: 13

### Re: 5G.11

Just in general to write the equations for Q you include products and reactants that are either aqueous or in the gas state.
Sun Jan 24, 2021 6:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: X Approximations
Replies: 23
Views: 66

### Re: X Approximations

So long as Ka or Kb is less than 1X10^-4 we can assume that the x is so small we can ignore the -x.
Sun Jan 24, 2021 6:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Question 3
Replies: 8
Views: 51

### Re: Sapling Question 3

CH3CH(OH)COOH <--> CH3CH(OH)COO- + H+. This is what the ionization of lactic acid looks like. After knowing this and setting up an ICE table you can find the concentration of H+. Finding that will allow you to find pH and pOH. The percent ionization is the concentration of H+ over the initial concen...
Sun Jan 24, 2021 6:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How to find the H+ from pH
Replies: 12
Views: 29

### Re: How to find the H+ from pH

Given a pH of x to find concentration just do 10^-x.
Sun Jan 24, 2021 5:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 5I 23
Replies: 2
Views: 14

### Textbook 5I 23

I solved this problem and found the answer was K=3.91. According to the answers the correct answer was 3.88. Can someone explain how they solved this problem because I'm not sure if I simply made a rounding error.
Sun Jan 17, 2021 6:39 pm
Forum: Ideal Gases
Topic: T variable in pv=nrt [ENDORSED]
Replies: 38
Views: 285

### Re: T variable in pv=nrt[ENDORSED]

For the T in pv=nrt, it should always stay in Kelvin.
Sun Jan 17, 2021 6:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Sapling Week 1 #6
Replies: 7
Views: 36

### Re: Sapling Week 1 #6

You solve for Q the same way you would solve for Kc ([P]/[R]). After finding Q compare it to the Kc. If Q>Kc the reaction shifts towards the reactants. If Q<Kc the reaction shifts towards the products.
Sun Jan 17, 2021 6:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Question 4
Replies: 5
Views: 37

### Re: Sapling Question 4

I'm not sure why you keep getting different answers, but after you set up your ICE table and solve for the quadratic equation, you'll be able to find the partial pressures for the individual products and reactants. To find the total pressure find the sum of partial pressures. Hope this helps.
Sun Jan 17, 2021 6:27 pm
Forum: Ideal Gases
Topic: Sapling Question #4
Replies: 11
Views: 71

### Re: Sapling Question #4

Hi! I remember getting stuck on this problem as well. After setting up the ice table and finding the partial pressures, all you have to do to find the total pressure is just find the sum of partial pressures.
Sun Jan 17, 2021 6:25 pm
Forum: Student Social/Study Group
Topic: Sapling Homework
Replies: 15
Views: 36

### Re: Sapling Homework

It looks like in general what's due on sapling is whatever we learned a week ago.
Sun Jan 10, 2021 1:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Definition of an Inert Gas
Replies: 6
Views: 26

### Re: Definition of an Inert Gas

Inert gases are ones that do interact with the reactants or products because they have completely filled valence shells meaning they cannot contribute to any change in the direction of the reaction.
Sun Jan 10, 2021 1:52 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient Definition
Replies: 7
Views: 23

### Re: Reaction Quotient Definition

Unless the problem tells us the reaction is at equilibrium, we'd be using Q. K is only used when it the reaction is at equilibrium. If we are given K and are asked to find Q after a change has occurred in the reaction we can know what direction the reaction will move, either towards reactants or pro...
Sun Jan 10, 2021 1:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW Question
Replies: 8
Views: 42

### Re: HW Question

I used Hess's Law first by adding 2NH3+3I2↽−−⇀N2+6HI with an unknown Kx and N2+3H2↽−−⇀2NH3 with a given Kc. This leaves you with 3H2+3I2↽−−⇀6HI with a Ky=Kx*Kc. This equation is just H2+I2↽−−⇀2HI multiplied by 3 and we already are given the Ka for this. So Ky=Ka^3. From there it is just solving the ...
Sun Jan 10, 2021 1:37 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Endothermic vs Exothermic Stabilities
Replies: 8
Views: 91

### Re: Endothermic vs Exothermic Stabilities

I think you would be right mainly because stability has to do with energy, molecules and compounds that are of lower energy are more stable than those with higher energy.
Sun Jan 10, 2021 1:34 pm
Forum: Ideal Gases
Topic: PV=nRT and concentration
Replies: 27
Views: 117

### Re: PV=nRT and concentration

As everyone else has said, given that molarity is simply moles/liter, liters being a a unit of volume, n/V provides us the molar concentration.
Fri Dec 11, 2020 10:19 pm
Forum: Student Social/Study Group
Topic: Final
Replies: 18
Views: 114

### Re: Final

It says within that Finals PDF he shared with us about all the review hours this: "Questions will come from the textbook homework listed in the syllabus." So presumably going through the textbook is a smart idea.
Fri Dec 11, 2020 10:15 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determining Which is More Acidic Between 2 Weak Acids
Replies: 3
Views: 50

### Determining Which is More Acidic Between 2 Weak Acids

In the textbook section 6c problem 21 asks to determine between two weak acids which is a stronger acid. How would I be able to tell that formic acid is slightly stronger than acetic acid?
Fri Dec 11, 2020 10:04 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Textbook 3f 5
Replies: 6
Views: 60

### Textbook 3f 5

Part c of this problem asked between CHF3 and CHI3 which is likely to have the higher normal melting point. I chose CHF3 because F has the highest electronegativity and as result it would create a stronger dipole moment than I. According to the textbook the answer is CHI3. Could someone explain why?
Fri Dec 11, 2020 9:56 pm
Forum: Electronegativity
Topic: Textbook Problem: 2D#3
Replies: 3
Views: 28

### Textbook Problem: 2D#3

This problem asked which of among a group of compounds had primary ionic character. Among the options were BeBr2 and BaBr2. The answer was BaBr2, which I presume was because there was a bigger electronegative difference between Ba and Br than Be and Br. Beyond simply knowing the electronegativities ...
Fri Dec 11, 2020 9:43 pm
Forum: Amphoteric Compounds
Topic: Tricks for Determining
Replies: 5
Views: 65

### Tricks for Determining

Hey. Does anyone know what any easy way is to determine whether or not a compound is amphoteric or not? As of now all I have is drawing out the structure and seeing if there is a portion of the compound that can act as a lewis base and another part that can act as a lewis acid.
Mon Dec 07, 2020 11:22 am
Forum: Student Social/Study Group
Topic: Finals Study Things
Replies: 27
Views: 190

### Re: Finals Study Things

Thank you so much! This is really amazing and helpful.
Sun Dec 06, 2020 3:34 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 90

I may be wrong, but I believe that the exact cutoff or grade breakdown depends on how (or whether) the professor curves the grades at the end of the quarter, based on how most students did, which will likely depend on the final quite a bit. Does anyone know what the curve has been like for this cla...
Sun Dec 06, 2020 3:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Partial Credit on the Final
Replies: 6
Views: 67

### Re: Partial Credit on the Final

Someone please correct me if I am wrong, but I do not believe we will be given any opportunities for partial credit on the final as the exam is multiple choice. Unless the final exam changes to free response, there likely will not be any chance for partial credit. If I remember correctly for our fi...
Sun Dec 06, 2020 3:26 pm
Forum: Student Social/Study Group
Topic: Practice Exams
Replies: 3
Views: 16

### Practice Exams

In preparation for the finals, does anybody know if there some practice exams for Chem 14A that I can take a look at and where I could find them?
Sun Dec 06, 2020 3:21 pm
Forum: Naming
Topic: Sapling 1
Replies: 34
Views: 166

### Re: Sapling 1

In regards to putting things in alphabetical order, first do that for name of each atom or molecular compound, then add prefixes.
Sun Dec 06, 2020 3:18 pm
Forum: Naming
Topic: Prefixes for parts outside of Coordination Compound
Replies: 7
Views: 54

### Prefixes for parts outside of Coordination Compound

For an example like this:[Co)NH3)5Cl]Cl2. Is there a reason why it ends with chloride rather than dichloride?
Sun Nov 29, 2020 7:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent
Replies: 9
Views: 62

### Re: Bent

Yeah as everyone else has mentioned, bent and angular are one and the same.
Sun Nov 29, 2020 7:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #3 Bond Angle
Replies: 8
Views: 72

### Re: Sapling #3 Bond Angle

I think it helps to rethink of any lone pairs as attached molecules. For this problem there would then be 6 molecules around the central atom. In order for them to be evenly distributed and the farthest away from each other they possibly can, each attached molecule or atom must be 90 degrees away fr...
Sun Nov 29, 2020 7:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: #13 Sapling Week 8
Replies: 18
Views: 100

### Re: #13 Sapling Week 8

It is a tetrahedral so I imagine it is just a spelling error.
Sun Nov 29, 2020 6:54 pm
Forum: Hybridization
Topic: Sapling #11
Replies: 19
Views: 122

### Re: Sapling #11

In terms of this problem, a lot of the other people who have responded gave great answers when it came to determining hybridization. For me when I started, I looked at only one the phosphorous atoms, saw it had 4 regions of electron density and then checked a different one. Once I saw they all have ...
Sun Nov 29, 2020 6:49 pm
Forum: Hybridization
Topic: Sapling #18
Replies: 10
Views: 100

### Re: Sapling #18

Basically it is asking if the hydrogens on both ends of the molecule are all on say the x axis. Or is one end on the x plane and the other two hydrogens are on the y or z planes.
Sun Nov 22, 2020 2:35 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and pi
Replies: 3
Views: 22

### Re: Sigma and pi

I would say for the purposes of this class, these are the only types of bonds we need to know. Maybe further chemistry others will come up but for now these will suffice.
Sun Nov 22, 2020 2:30 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Intermolecular forces Hydrogen Bonding
Replies: 5
Views: 54

### Re: Intermolecular forces Hydrogen Bonding

What's the difference between dipole-dipole and dipole-induced dipole? The difference is that a dipole-dipole interaction occurs between two molecules that are always polar. Whereas in a dipole-induced dipole interaction, a polar molecule is interacting with a nonpolar molecule which temporarily, d...
Sun Nov 22, 2020 2:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #4
Replies: 5
Views: 49

### Re: Sapling #4

If it helps imagine a trigonal bipyramidal and just remove one the outer atoms. Leaving you with four outer atoms and 1 lone pair.
Sun Nov 22, 2020 2:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Scores
Replies: 28
Views: 210

### Midterm 2 Scores

Hi, I was wondering when we could expect to get back our scores for the second midterm.
Fri Nov 20, 2020 11:25 pm
Forum: Resonance Structures
Topic: Atom Connectivities
Replies: 5
Views: 42

### Atom Connectivities

For week 7/8 sapling problems, number 17 asks about resonance structures. It mentions in the solutions that resonance structures must all have the same atom connectivities. Could anyone explain to me what that is?
Sun Nov 15, 2020 8:07 pm
Forum: Ionic & Covalent Bonds
Replies: 6
Views: 44

From how I understand it, the covalent radius can be half the distance between the nuclei of any two covalently bonded atoms while atomic radius specifically refers to when it is half the distance between the nuclei of two of the same atom.
Sun Nov 15, 2020 7:59 pm
Forum: Electronegativity
Topic: polar vs nonpolar
Replies: 19
Views: 91

### Re: polar vs nonpolar

Beyond being given the specific electronegativity an easy way I find that generally works for finding out if a molecule is polar or nonpolar is to draw out the lewis structure, specifically with shape in mind (ie including bends due to lone paired electrons). If the molecule is perfectly symmetrical...
Sun Nov 15, 2020 7:50 pm
Forum: Ionic & Covalent Bonds
Topic: D orbitals
Replies: 3
Views: 29

### D orbitals

Why is it that for Ag(+1) the electron configuration goes from [Ar] 4s2 3d9 to [Ar] 3d10 rather than [Ar] 4s1 3d9?
Sun Nov 15, 2020 7:44 pm
Forum: Electronegativity
Topic: Given for test
Replies: 3
Views: 18

### Given for test

For some of the textbook problems in order to solve them, I needed to look at the chart in the textbook that provided the electronegativity for each specific atom. Does anyone know if on the test we will be given problems where the electronegativities are given or are we just meant to know the gener...
Sun Nov 15, 2020 7:40 pm
Forum: Trends in The Periodic Table
Topic: Solidified Gas
Replies: 1
Views: 17

### Solidified Gas

In the textbook it mentions Van der Waals radii are used for the noble gases. Specifically half the distance between neighboring atoms in a sample of solidified gas. What is solidified gas?
Sun Nov 08, 2020 7:26 pm
Forum: Resonance Structures
Topic: Valence Electrons [ENDORSED]
Replies: 43
Views: 328

### Re: Valence Electrons[ENDORSED]

From my understanding all the families have the same amount of valence electrons, so in order to know say how many valence electrons bromine has, all you would need to know is how many valence electrons fluorine has (1). Also I think it's just because Lavelle so much practice doing chemistry.
Sun Nov 08, 2020 7:19 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Covalent Bonds with Ionic Character/Polar
Replies: 3
Views: 14

### Covalent Bonds with Ionic Character/Polar

Are compounds that have covalent bonds with strong ionic character basically the same thing as a polar molecule, such as water? Is there any difference?
Sun Nov 08, 2020 7:11 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Question Count
Replies: 17
Views: 106

### Midterm 2 Question Count

Does anyone know how many questions will be on Midterm 2? Will it be around the same as Midterm 1, and will we get a free bonus question again?
Sun Nov 08, 2020 7:01 pm
Forum: Electronegativity
Topic: Silver Halides
Replies: 5
Views: 16

### Silver Halides

During lecture Dr. Lavelle mentioned how silver halides have increasing covalent characteristics and are less soluble as the size of anion increases. Is there any specific reason he brought this up as an example, are the covalent properties more easily noticeable in these compared to other salts.
Sun Nov 08, 2020 6:50 pm
Forum: Coordinate Covalent Bonds
Topic: Lewis Diagram
Replies: 5
Views: 60

### Lewis Diagram

When drawing a a Lewis Diagram for a molecule that has a coordinate covalent bond, is there an specific notation for it, or are we supposed to figure that out based on knowledge of the individual atoms in the structure and the amount of valence electrons each has?
Sun Nov 01, 2020 1:50 pm
Forum: Ionic & Covalent Bonds
Topic: Sampling 28
Replies: 10
Views: 54

### Re: Sampling 28

I believe in most of the sapling problems we're given both a number/letter, for example 4s. This provides you with the information for both the n an l values. N being simply the number. And the letter tells you the l value. When it is s l=0, p l=1, d l=2, f l=3 and so on.
Sun Nov 01, 2020 1:47 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 2
Views: 46

### Re: Electron Affinity

From my understanding it is kind of similar to the principle of an electron falling back to a lower level. When that occurs energy is released from electron as it moves from say 5 to 1. Similarly here an electron is moving from out of a shell back into one which I think means a similar release of en...
Sun Nov 01, 2020 1:43 pm
Forum: Ionic & Covalent Bonds
Topic: Is ionic or covalent stronger?
Replies: 31
Views: 397

### Re: Is ionic or covalent stronger?

I believe in order of strength at the molecular level it goes, from strongest to weakest: ionic, covalent, polar, Van der Waals forces.
Sun Nov 01, 2020 1:35 pm
Forum: Student Social/Study Group
Topic: Favorite TV shows
Replies: 178
Views: 935

### Re: Favorite TV shows

Over the summer I watched all of Futurama, I highly recommend it. The Mandalorian Season 2 just started on Friday so if you haven't watched that that's another fun show.
Sun Nov 01, 2020 1:31 pm
Forum: Student Social/Study Group
Topic: Test Scored for Midterm 1
Replies: 49
Views: 382

### Re: Test Scored for Midterm 1

So has anybody yet received their score for the midterm? Haven't all discussion sections taken it as of today?
Mon Oct 26, 2020 8:08 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Inconsistencies in Delta Values
Replies: 4
Views: 53

### Inconsistencies in Delta Values

For the Heisenberg Indeterminacy Module, number 23 asks you to find the delta V given that the position is +/- 5. In order to get this question right you need to then make your delta X = 10. This contradicts what is said in the textbook. In 1B problem 27 you are similarly asked to find delta V given...
Sat Oct 24, 2020 1:29 pm
Forum: Student Social/Study Group
Topic: Midterm Prep
Replies: 15
Views: 99

### Re: Midterm Prep

Evie Li_3H wrote:I think someone said the midterm will be about 10 questions long? One of the TAs said probably no more than 12.

I believe my TA mentioned it was going to be somewhere between 25-30 questions. In terms of studying I did up to question 19 in Sapling and am taking notes from the textbook.
Sat Oct 24, 2020 1:26 pm
Forum: Student Social/Study Group
Topic: Study tips?
Replies: 9
Views: 90

### Re: Study tips?

Most of my studying for this class revolves around the textbook. I'm going through it, taking notes, and doing the practice problems that Lavelle has recommended. I also did up to question 19 on Sapling.
Sat Oct 24, 2020 1:24 pm
Forum: Student Social/Study Group
Topic: Textbook Information
Replies: 2
Views: 37

### Textbook Information

For the midterm how much information from the textbook do we need to know? Is it important we know all the scientists mentioned in the book, not just the ones mentioned in lectures, and their experiments?
Wed Oct 21, 2020 5:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Sapling Problem 19
Replies: 1
Views: 27

### Sapling Problem 19

This problem asks you to find the minimum uncertainty in an electron's velocity given the position is known within 15 angstroms. When they say this, do they mean the delta position is +/-15 or +/-7.5?
Mon Oct 19, 2020 6:25 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling Week 2/3 Problem 11
Replies: 2
Views: 26

### Sapling Week 2/3 Problem 11

For the sapling homework, part of question 11 mentioned that a red line was emitted with a wavelength at 656.3 nm for hydrogen. Given that it was a visible light I knew that it was part of the Balmer Series but I was not able to solve the problem until I searched up and saw an image of the actual Ba...
Sun Oct 18, 2020 6:48 pm
Forum: Photoelectric Effect
Topic: Wave Properties of Electrons
Replies: 3
Views: 19

### Re: Wave Properties of Electrons

I believe it is referring to how electrons move. While traveling they do not take a linear path, but rather one that comes in the form of a wave.
Sun Oct 18, 2020 6:45 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Post Module Q14
Replies: 1
Views: 20

### Heisenberg Uncertainty Post Module Q14

Question 14 was: For large everyday objects does Heisenberg's uncertainty (indeterminacy) principle play any measurable role? I chose C which was: No, the uncertainties in position, speed, and momentum of a stationary object are not noticeable or measurable. The answer was incorrect so I'm assuming ...
Sun Oct 18, 2020 6:38 pm
Forum: Photoelectric Effect
Topic: In a Vacuum
Replies: 7
Views: 35

### In a Vacuum

In order for the photoelectric effect experiment to be done correctly, one of the conditions was that it needs to occur within a vacuum. What specifically happens if that isn't the case. I understand that the electrons will interact with air molecules. Do these interactions simply pull the electrons...
Wed Oct 14, 2020 2:18 pm
Forum: Photoelectric Effect
Topic: What happens to emitted electrons?
Replies: 1
Views: 42

### What happens to emitted electrons?

In the experiment that was used to determine the photoelectric effect, the electrons were emitted from the copper. What happened to these electrons afterwards. Is it similar to what happens when an electron moves up a level in an atom, and it will eventually return to the copper? Also does the coppe...
Wed Oct 14, 2020 2:10 pm
Topic: Black Body Black Holes?
Replies: 4
Views: 52

### Black Body Black Holes?

Based on the lecture, a black body was described as being able to absorb all frequencies of light but was a purely theoretical concept. That being said though isn't that very similar to a black hole, given that no light is able to escape from a black hole and therefore absorbs all light? Basically I...
Sat Oct 10, 2020 3:21 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Week 1 #8
Replies: 23
Views: 234

### Re: Sapling Week 1 #8

Something that helped me figure out the molecular formula was drawing it out for myself. Having it on paper made it a lot easier for me to count the number of carbons, oxygens, and hydrogens there were. From there you simply need to multiply the number of each atom by their respective atomic weight ...
Sat Oct 10, 2020 3:13 pm
Forum: Significant Figures
Topic: How to deal with significant figures in decimals with zeros.
Replies: 20
Views: 194

### Re: How to deal with significant figures in decimals with zeros.

Here's a good link that explains what parts of a number are significant figures and which parts aren't. Also if you're ever really unsure as to the specific significant figures of certain number, this site provides you with a quick way to check if you got the number significant figures correct, afte...
Sat Oct 10, 2020 3:03 pm
Forum: Limiting Reactant Calculations
Topic: Last Question on the Sapling Hw (Week 1)?
Replies: 12
Views: 158

### Re: Last Question on the Sapling Hw (Week 1)?

Unless you just had chemical formulas and molar masses memorized, this was the kind of information that we had to look up in order to complete the problem. Had we been given the chemical formulas we could have been expected to find the molar mass by going through and adding each atom's individual mo...
Fri Oct 09, 2020 3:58 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reagents
Replies: 10
Views: 117

### Re: Limiting Reagents

Thanks everyone for your replies. So if they can be used interchangeably, is there any term for the reactant in excess, or do we refer to it as such.
Wed Oct 07, 2020 10:27 am
Forum: Limiting Reactant Calculations
Topic: Limiting Reagents
Replies: 10
Views: 117

### Limiting Reagents

Hi, can some please clarify the difference between the limiting reagent and the limiting reactant. The limiting reagent is just the reactant that is in excess correct?