Search found 41 matches

by Manpreet Singh 1N
Fri Mar 17, 2017 1:34 pm
Forum: Stereochemistry in Organic Compounds (Chirality, Stereoisomers, R/S, d/l, Fischer Projections)
Topic: Cis vs. trans
Replies: 1
Views: 783

Re: Cis vs. trans

On one of the practice finals, you were able to get credit using either or but it looks more concise when using E and Z for IUPAC naming
by Manpreet Singh 1N
Fri Mar 17, 2017 1:32 pm
Forum: *Cycloalkenes
Topic: When to use Z vs. E?
Replies: 4
Views: 692

Re: When to use Z vs. E?

More specifically Z is used when the high priority groups are on the same side and E is when the high priority are on the opposite side. The high priority group is determined by atomic number
by Manpreet Singh 1N
Wed Mar 15, 2017 10:35 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 186
Views: 39342

Re: Saying Thank You to Dr. Lavelle

Dr.Lavelle, I just want to say thank you for all the effort you have put in to make sure we understand chemistry. Because of my lack of a strong chemistry background from high school, the idea of taking chemistry for two years scared me. However since the first day of chem 14A with you, your class h...
by Manpreet Singh 1N
Tue Mar 07, 2017 12:25 pm
Forum: *Alkanes
Topic: #1 quiz 3 preparation
Replies: 2
Views: 272

Re: #1 quiz 3 preparation

Aadding on, we use the carbon count from right to left because it gives us a small number. From left to right the isoporpyl would have been on the 7th carbon, but from right to left it is attached to the 4th carbon. Professor Lavelle said we want the smaller number when writing the name of the compo...
by Manpreet Singh 1N
Mon Feb 27, 2017 8:24 am
Forum: Balancing Redox Reactions
Topic: Three-step electrochemical reactions
Replies: 1
Views: 184

Re: Three-step electrochemical reactions

Hello,

I am not completely sure where they exist, but there are reactions that require three half-reactions. Due to this, there are ways to solve for them. Here is a link I found.
http://www.chemteam.info/Redox/Redox-Th ... tions.html
by Manpreet Singh 1N
Mon Feb 20, 2017 11:37 pm
Forum: General Rate Laws
Topic: Hw 15.27 and 15.35
Replies: 2
Views: 255

Re: Hw 15.27 and 15.35

Hello,

We cant use the same process because it 15.27 the reaction is in 1st order but it 35 it is in second order. So it 27, the equation we used is ln[A]=-kt+ln[A0]. But for a second order reaction the equation would be 1/[A]=kt+1/[A0].
by Manpreet Singh 1N
Mon Feb 06, 2017 8:27 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.27
Replies: 1
Views: 200

Re: 14.27

Hello, For this problem, we want the standard potential for U^4+ +4e- ----> U since we don't have that exact standard potential, we can use the information we have so we have: U^4+ +e- ----> U^3+ E^o=-0.61 U^3+ +3e- -----> U E^o=-1.78 When we add, the U^3+ cancels out because they are on opposite si...
by Manpreet Singh 1N
Mon Feb 06, 2017 8:17 am
Forum: Balancing Redox Reactions
Topic: Help on problem 14.17
Replies: 4
Views: 484

Re: Help on problem 14.17

We also multiple the second half-reaction by 5 because we want the electrons to cancel out, so we are left with the only the molecules.
by Manpreet Singh 1N
Mon Jan 30, 2017 2:28 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Winter 2013 Midterm #5.B
Replies: 1
Views: 210

Re: Winter 2013 Midterm #5.B

Hello,

My logic for this problem is that the molecule with the greater molar mass has the greatest molar entropy because the more massive the gas molecule, the more disordered it can be.

Hope that helps :)
by Manpreet Singh 1N
Mon Jan 30, 2017 8:14 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 Number 75 b
Replies: 1
Views: 295

Re: Chapter 8 Number 75 b

Hello,

Yes you are correct. You can write the bond enthalpies for both reactants and products, but when you do that, you see that all the C-H bonds cancel out.

Hope that helps :)
by Manpreet Singh 1N
Mon Jan 23, 2017 8:24 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Irreversible and reversible reactions
Replies: 2
Views: 268

Re: Irreversible and reversible reactions

Reversible reactions at equilibrium means that once the reactants form the products, the products can form the reactions again using the same amount of energy. A irreversible reaction at equilibrium means that once the reactants make the products, the reactants can not be formed again by the products.
by Manpreet Singh 1N
Tue Jan 17, 2017 10:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.29: Need Clarification [ENDORSED]
Replies: 3
Views: 449

Re: Homework 8.29: Need Clarification [ENDORSED]

Hello, My logic may be wrong, but the units for molar heat capacity are J*K^-1*mol^-1. I remember Professor Lavelle saying that the more mass something has the more the heat capacity. So since NO2 has one more oxygen (one more atom), there are more bonds that can absorb the energy that is added. Hop...
by Manpreet Singh 1N
Tue Jan 17, 2017 10:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Isolated [ENDORSED]
Replies: 1
Views: 213

Re: Isolated [ENDORSED]

I am pretty sure, scientists can get very close to having a perfectly isolated system. My TA used the example of a thermos as an isolated system.
by Manpreet Singh 1N
Tue Jan 17, 2017 10:00 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Changing Energy of a System [ENDORSED]
Replies: 1
Views: 240

Re: Changing Energy of a System [ENDORSED]

Hello, Yes heating and cooling would be only the only way to change energy for a closed system because in a closed system no substance can go in or out, just heat energy can enter and escape. While an open system, because it is open can be changed by substance and by cooling and heating. However, in...
by Manpreet Singh 1N
Tue Jan 17, 2017 9:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies to Calculate Total Enthalpy Change [ENDORSED]
Replies: 2
Views: 251

Re: Using Bond Enthalpies to Calculate Total Enthalpy Change [ENDORSED]

Hello,

I feel like in order to know what bonds are broken and formed there is some extent of knowledge necessary. Adding on, the wording of the question and the chemical formula should tell you which bonds are broken and which are formed.

Hope that helps :)
by Manpreet Singh 1N
Wed Jan 11, 2017 2:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Workbook
Replies: 2
Views: 258

Re: Workbook

That is correct. The practice quizzes are in our course reader. Professor Lavelle said that there will not be workbooks this quarter because he has too many students and it would have been very difficult for the TAs to be able to grade them.
by Manpreet Singh 1N
Mon Nov 28, 2016 2:50 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs Lewis Acid Definition
Replies: 2
Views: 285

Re: Bronsted vs Lewis Acid Definition

A Bronsted Acid is an acid that donates a proton (H+), while a Lewis acid accepts electrons. I like to think that acids like to have a negative charge and therefore either loses a proton or accepts an electron.

Hope that helps :)
by Manpreet Singh 1N
Mon Nov 28, 2016 1:32 pm
Forum: Administrative Questions and Class Announcements
Topic: Final
Replies: 1
Views: 307

Re: Final

Professor Lavelle posted it under announcement on chemistry community. But here it is: Chem 14A Final Exam 3-6pm, Sunday, December 4. Students MUST go to their assigned room. 14A-1, 11am class: Last name A-L in CS50. Last name M-Z in LAKRETZ 110. 14A-3, 1pm class: Last name A-L in CS24. Last name M-...
by Manpreet Singh 1N
Mon Nov 28, 2016 1:10 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 3
Views: 456

Re: Bronsted Acids and Bases

Adding on, Bronsted Acid and Bases deal with donating or accepting protons, while Lewis acids and bases deal with accepting or donating electrons.
by Manpreet Singh 1N
Tue Nov 22, 2016 6:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Why are they using the energy levels like this?
Replies: 3
Views: 520

Re: Why are they using the energy levels like this?

In this question, it talks about the UV spectrum, which falls under the Lyman series. The Lyman series has a n final of 1. On the other hand, the Balmer series (visible light) has a n final of 2.

Hope this helps :)
by Manpreet Singh 1N
Tue Nov 22, 2016 6:04 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Percentage dissociation
Replies: 1
Views: 231

Re: Percentage dissociation

Hello,

When the percent dissociation is greater than 5%, we can not approximate. We would have to use the quadratic equation to solve for X, to have a more precise concentration.

Hope that helps :)
by Manpreet Singh 1N
Tue Nov 22, 2016 6:02 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH and pOH difference
Replies: 1
Views: 755

Re: pH and pOH difference

Hello,
So pH is the measure of hydrogen ion concentration, [H+], while pOH is a measure of the hydroxide ion concentration, [OH-]. The scales for both are 1-14. However in most cases, the question will ask for pH. So remember that pH+pOH=14. So pH=14-pOH.
by Manpreet Singh 1N
Mon Nov 21, 2016 12:47 pm
Forum: Conjugate Acids & Bases
Topic: Chapter 12 Question 1
Replies: 3
Views: 409

Re: Chapter 12 Question 1

Hello,

Since acids are proton acceptors, it would gain a proton. Since it is negatively charged to begin with, adding a H+ would neutralize it. So the answer would be H2CO3

Hope this helps :)
by Manpreet Singh 1N
Mon Nov 14, 2016 1:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Problem 17.29
Replies: 1
Views: 216

Re: Homework Problem 17.29

Hello,

In lecture, Professor Lavelle said that if the complex has a negative charge(which is rare), the Transition metal will end in ate.

Hope that helps :)
by Manpreet Singh 1N
Mon Nov 14, 2016 1:13 pm
Forum: *Molecular Orbital Theory Applied To Transition Metals
Topic: A Question about Molecular orbitals
Replies: 2
Views: 388

Re: A Question about Molecular orbitals

Hello,

My TA did a example of F2 and F2- in our discussion. He said that F2- is weaker because it has one more anti-bonding and because it is paramagnetic. So when we compare two molecules, the one that is paramagnetic is weaker.

Hope that helps:)
by Manpreet Singh 1N
Mon Nov 07, 2016 9:40 pm
Forum: Naming
Topic: Iron [ENDORSED]
Replies: 6
Views: 700

Re: Iron [ENDORSED]

Hello, First of all it is not a stupid question. Secondly, professor Lavelle mentioned in lecture than when a complex has a negative charge (which is pretty uncommon) it has a anion. For this case, the complex has a 4- charge. Adding on the CN has a -1 charge. Since there are 6 of them, the charge i...
by Manpreet Singh 1N
Mon Nov 07, 2016 9:36 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordinate Number
Replies: 3
Views: 384

Re: Coordinate Number

Hello, The coordination number helps you find out how many ligands are connected to the central atom and helps you determine the overall shape of the specific complex. So in other words, it helps you find how many donor atoms there are. So to answer your question, yes the coordination number is affe...
by Manpreet Singh 1N
Mon Nov 07, 2016 9:24 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Why do electronegative atoms have lower energy?
Replies: 1
Views: 806

Re: Why do electronegative atoms have lower energy?

Hello, The more electronegative atom has lower energy because the row of electronegativity relates to the charge of the nucleus. Therefore, the elements on the right (more charged nucleus) are more electronegative. That means that the more electronegative the atom is, the closer the electrons orbita...
by Manpreet Singh 1N
Mon Oct 31, 2016 5:29 pm
Forum: Lewis Structures
Topic: 2012 Midterm Q5b, part (e)
Replies: 2
Views: 269

Re: 2012 Midterm Q5b, part (e)

Hello,

O does have a slightly lower ionization energy, but I remember Professor Lavelle saying that O can never be a central atom.

Hope that helps :)
by Manpreet Singh 1N
Mon Oct 24, 2016 9:23 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: f orbitals
Replies: 1
Views: 251

Re: f orbitals

Hello,

For Hf, the atomic number is 72. The lanthanides have atomic numbers 58-71, which is before 71. Therefore the f orbital is full and the electron configurations for Hf=[Xe]4f^14 5d^2 6s^2

Hope that helps :)
by Manpreet Singh 1N
Mon Oct 24, 2016 9:04 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ml configuration for d subshells
Replies: 1
Views: 197

Re: ml configuration for d subshells

Hello,

For the d-shell, l=2, the notation for ml is -2,-1,0,1,2

Hope this helps :)
by Manpreet Singh 1N
Mon Oct 17, 2016 7:29 pm
Forum: Resonance Structures
Topic: Homework 3.71 [ENDORSED]
Replies: 1
Views: 226

Re: Homework 3.71 [ENDORSED]

Hello, In class Professor Lavelle said that the lewis structure that has the most of the elements that have a formal charge of 0 will make the greater contribution because it is the most stable. So it part a) Xe and F have a formal charge of 0 in the first one, while the second one has Xe with -1 an...
by Manpreet Singh 1N
Mon Oct 17, 2016 4:31 pm
Forum: Ionic & Covalent Bonds
Topic: Ch 3 #9,11 [ENDORSED]
Replies: 5
Views: 450

Re: Ch 3 #9,11 [ENDORSED]

Hello, So basically for this question, we are told to find a M (a metal) with the corresponding configurations. So for part a of #9. it is [Ar]3d^7. To begin we look at the noble gas [Ar], that is our starting point. Then we look at the next part, which is 3d^7. The first row of the d series is 3d. ...
by Manpreet Singh 1N
Mon Oct 10, 2016 7:47 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: HW 1.15
Replies: 3
Views: 305

Re: HW 1.15

Hello, The question tells us that a line at 102.6nm was observed in the ultraviolet spectrum. This brings in the Balmer and Lyman series. We know that Balmer is visible light with n1=2, while Lyman is UV with n1=1. I think it is something we have to remember. we can solve this problem by using v=R(1...
by Manpreet Singh 1N
Mon Oct 10, 2016 7:34 am
Forum: Properties of Light
Topic: Homework question 1.27
Replies: 2
Views: 266

Re: Homework question 1.27

To begin the problem we need to find the energy of the light. So we use the E=(hc)/wavelength so energy= ((6.626x10^-34 Js)(3x10^8m/s))/(420x10^9m) I changed the units of wavelength from nm to m, so that is why I multiplied 10^-9 to the given wavelength. We get the energy to be about 4.7x10^-19J. I ...
by Manpreet Singh 1N
Mon Oct 10, 2016 7:33 am
Forum: Properties of Light
Topic: Homework question 1.27
Replies: 2
Views: 266

Re: Homework question 1.27

To begin the problem we need to find the energy of the light. So we use the E=(hc)/wavelength so energy= ((6.626x10^-34 Js)(3x10^8m/s))/(420x10^9m) I changed the units of wavelength from nm to m, so that is why I multiplied 10^-9 to the given wavelength. We get the energy to be about 4.7x10^-19J. I ...
by Manpreet Singh 1N
Mon Oct 03, 2016 10:58 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Question 1.43
Replies: 2
Views: 347

Re: Question 1.43

Hello, h is a constant. However in this answer manual it uses h bar, which is equal to h/(2pi) when you do the math (6.626x10^-34)/(2pi)=1.0546x10^-34. just to make it clear (h bar)/2 is the same as h/(4pi). in the solution manual it has 1/2 separated. But if you do it with h/4pi instead, you should...
by Manpreet Singh 1N
Mon Oct 03, 2016 10:41 pm
Forum: Properties of Light
Topic: HW Question Ch #27 [ENDORSED]
Replies: 5
Views: 787

Re: HW Question Ch #27 [ENDORSED]

To begin the problem we need to find the energy of the light. So we use the E=(hc)/wavelength so energy= ((6.626x10^-34 Js)(3x10^8m/s))/(420x10^9m) I changed the units of wavelenth from nm to m, so that is why I multiplied 10^-9 to the given wavelength. We get the energy to be about 4.7x10^-19J. I l...
by Manpreet Singh 1N
Mon Sep 26, 2016 1:51 pm
Forum: Photoelectric Effect
Topic: Photo electric effect
Replies: 3
Views: 427

Photo electric effect

I am stuck on this question from the post assessment. Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. A. What is the kinetic energy of the ejected electron? I think I...

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