Search found 52 matches

by paytonm1H
Tue Feb 12, 2019 11:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 47
Views: 1660

Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!

can someone explain the reasoning behind the three steps to solve for enthalpy of #12B
by paytonm1H
Mon Feb 11, 2019 9:48 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Equation for temperature change, 4F.11
Replies: 4
Views: 25

Re: Equation for temperature change, 4F.11

I just experienced the same thing. I don't understand why deltaS=nRln(T2/T1) is valid in this problem.
by paytonm1H
Mon Feb 11, 2019 9:41 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 7th edition 4F.11
Replies: 3
Views: 37

7th edition 4F.11

In this question, it asks you to calculate net change in entropy for a change in volume and temperature, but you aren't given the moles of gas. It tells you to assume ideal behavior (P=1.00atm), and the answer key also says to assume 1 mol of gas. Is this always true for gas at ideal behavior?
by paytonm1H
Sat Feb 09, 2019 10:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4.19 7th edition
Replies: 1
Views: 8

4.19 7th edition

4.19 asks for the molar kinetic energy of Kr(g) at two temps 1.0C apart, in which the difference is the molar heat capacity of Kr(g).

The solutions manual gives the average kinetic energy = (3/2)RT. Did we cover this in class? Where does this equation come from?
by paytonm1H
Sat Feb 09, 2019 9:56 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4.15 7th edition
Replies: 1
Views: 12

4.15 7th edition

In the final step pf 4.15 in the solutions manual is said
-2000J=(-4.184 J/Cg)(800g)(deltaT)

I understand they are using the q(water) = -q(zinc oxidation) = mCp(deltaT)

Where are they getting the 800g water from?
by paytonm1H
Sat Feb 09, 2019 8:30 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 7th edition 4E.5
Replies: 3
Views: 22

7th edition 4E.5

Hi all. I am currently working on 4E.5 in the 7th edition textbook. The question asks to estimate the reaction enthalpy using bond enthalpies for the formation of benzene: 3C2H2(g) --> C6H6(g) 3 C-C triple bonds are broken and 6 C-C 1.5 bonds are formed. Why isn't the formation of 6 C-H bonds includ...
by paytonm1H
Thu Feb 07, 2019 1:15 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Midterm topics
Replies: 3
Views: 31

Midterm topics

Hi all. I was wondering up to what part of the syllabus we will be tested on for the midterm. I have the seventh edition and I know that Lavelle said the midterm will cover thermodynamics to the end of entropy. Is that through section 4I in the textbook?
Thanks.
by paytonm1H
Thu Feb 07, 2019 12:07 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Problem 4A.9) 7th edition of the textbook [ENDORSED]
Replies: 3
Views: 186

Re: Problem 4A.9) 7th edition of the textbook [ENDORSED]

responding to the question on heat lost by ice = - heat gained by water... The hear gained by the water is not negative. This relationship is simply implying that the heat lost by the ice and the heat gained by the water are equal and opposite one another. So you can use that relationship to find th...
by paytonm1H
Thu Jan 24, 2019 8:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: converting between kp and kc
Replies: 4
Views: 25

Re: converting between kp and kc

The ideal gas law should be your go to:
PV=nRT
by paytonm1H
Wed Jan 23, 2019 9:40 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Writing equations for weak acids/bases
Replies: 3
Views: 18

Re: Writing equations for weak acids/bases

I would also caution to make sure your stoichiometric coefficients are correct when writing shorthand version of weak reactions.
by paytonm1H
Wed Jan 23, 2019 9:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp
Replies: 3
Views: 30

Re: Kp

I believe both will give you the correct answer, only as long as all of your partial pressures are in the same unit (either all bar or all atm).
by paytonm1H
Fri Jan 18, 2019 9:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.61 7th Edition
Replies: 1
Views: 17

5.61 7th Edition

In problem 5.61 the photosynthesis reaction is given: 6CO2(g) + 6H2O(l) --> C6H12O6(aq) + 6O2(g) Part (b) asks what the effect would be if the system was compressed. Since there are more moles on the product side (disregarding moles of water on reactant side), I would think that compression would sh...
by paytonm1H
Fri Jan 18, 2019 7:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.27 in 7th edition
Replies: 1
Views: 20

5I.27 in 7th edition

Hi all,
I am currently working through 5I.27 and keep getting 8.7119 or 0.0738 for x, but the answer key has 9.2 or 0.071 for x. I have the quadratic equation set up the same as the answer key but can't find any mistakes in my calculations. Has anyone else run into this problem?
Thanks!
by paytonm1H
Sun Jan 13, 2019 10:15 pm
Forum: Ideal Gases
Topic: K value
Replies: 8
Views: 62

Re: K value

K=1 means that the concentration of the products is equal to the concentration of the reactants at equilibrium. It's not impossible, its just not common in everyday chemical reactions.
by paytonm1H
Sun Jan 13, 2019 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure Solids and Liquids
Replies: 2
Views: 14

Re: Pure Solids and Liquids

My understanding is that because pure liquids remain extremely dilute and solids barely dissociate, their effects on equilibrium are disregarded. Therefore they are not included in the equilibrium constant.
by paytonm1H
Sat Jan 12, 2019 10:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3 example from book
Replies: 3
Views: 13

Re: 5G.3 example from book

My bad, I mean self test 5G.3A
by paytonm1H
Sat Jan 12, 2019 10:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3 example from book
Replies: 3
Views: 13

5G.3 example from book

In example 5G.3 in the 7th edition (page 401), it asks to find the equilibrium constant using the net ionic equation. Can someone help me understand how to do this? Or is this even relevant to what we have gone over in lecture?
Thanks!
by paytonm1H
Sun Dec 09, 2018 2:55 pm
Forum: Properties of Light
Topic: Snail velocity final problem
Replies: 3
Views: 108

Snail velocity final problem

When given the momentum of a gamma ray photon, how do you find the velocity of a 200g snail? How can photons have momentum when they are massless?
by paytonm1H
Sun Dec 09, 2018 2:51 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: Strength
Replies: 5
Views: 45

Re: Strength

Yes, ion-ion is stronger because an ionic bonds is stronger than an ion-dipole intermolecular bond
by paytonm1H
Sun Dec 09, 2018 10:22 am
Forum: Administrative Questions and Class Announcements
Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
Replies: 118
Views: 3543

Re: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]

Once again, thank you so much Lyndon! You are a life saver!!
by paytonm1H
Sun Dec 09, 2018 10:19 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizability/polarizing power test 3
Replies: 3
Views: 38

Re: polarizability/polarizing power test 3

polarizability increases down a group and decreases across a period, because more electronegative atoms are harder to remove an electron from

polarizing power decreases down a group and increases across a period, because smaller, more highly charged cations have greater power
by paytonm1H
Sat Dec 08, 2018 6:22 pm
Forum: Conjugate Acids & Bases
Topic: Conjugates of Weak Acids/Bases
Replies: 1
Views: 28

Re: Conjugates of Weak Acids/Bases

Weak acids and bases will be discussed more thoroughly in 14B. For the 14A final, a conceptual understand that weak acids and bases do not completely ionize will probably suffice. Only calculations on strong acids and bases where they completely ionize will be on the final.
by paytonm1H
Sat Dec 08, 2018 6:20 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: HOCl vs HOI
Replies: 9
Views: 58

Re: HOCl vs HOI

HOCl is stronger because Cl is more electronegative, pulling the electrons close towards it. This weakens the O-H bond, making it easier to lose a proton(H+).
by paytonm1H
Sat Dec 08, 2018 6:18 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: polydentate
Replies: 2
Views: 33

Re: polydentate

Transition metals can have expanded valence shells, so the ligands act as Lewis bases (donate electrons) to form coordinate covalent bonds. To find the coordination number, add up all the ligands attached to the central ion. Bidentate would attach at two places, so a bidentate ligand would count as ...
by paytonm1H
Sat Dec 08, 2018 6:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: radical
Replies: 5
Views: 48

Re: radical

Radicals have an unpaired electron, making them very reactive.
by paytonm1H
Sat Dec 08, 2018 6:15 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxyacids
Replies: 4
Views: 41

Re: Oxyacids

This is because the greater the oxidation number of the central atom, the stronger the acid. When the oxidation number of the central atom is high, it has a greater electron withdrawing power (pulling electrons towards it), hence weakening the O-H bond (making it easier to lose the H/proton).
by paytonm1H
Sat Dec 08, 2018 6:07 pm
Forum: Identifying Acidic & Basic Salts
Topic: salts of weak acids and bases
Replies: 4
Views: 47

Re: salts of weak acids and bases

Since salts as acids and bases are weak, there probably won't be much on the final asking about them (Lavelle said that we will only be tested on strong acids and bases, weak will be covered more in 14B). Conceptually, I believe we should know that salts containing acids will lower the solution pH a...
by paytonm1H
Fri Dec 07, 2018 11:48 pm
Forum: Calculating the pH of Salt Solutions
Topic: 6D.11
Replies: 1
Views: 37

6D.11

Hi all. In the 7th edition, question 6D.11 asks whether each salt has a pH greater than, less than, or equal to 7. Part (e) gives AlCl3. Why so small, highly charged cations react with water to form acidic solutions? The answer key says that the pH is less than 7 and gives the equation: AlH2O)6 3+(a...
by paytonm1H
Thu Dec 06, 2018 12:04 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.9 7th Edition
Replies: 1
Views: 50

6B.9 7th Edition

This problem gives you a table of varying [H30+], [OH-], pH, and pOH values and you are asked to fill in the rest. The first line gives the [H30+] concentration as 1.50 mol/L. When plugging that into -log[H30+], I get -0.176, however, the answer key says that the pH is 0.176 (positive). Can someone ...
by paytonm1H
Thu Dec 06, 2018 11:08 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Water
Replies: 2
Views: 19

Water

Does the pH of water increase or decrease with increasing temperature? Why?
by paytonm1H
Thu Dec 06, 2018 11:02 am
Forum: Amphoteric Compounds
Topic: acidic vs. basic vs. amphoteric
Replies: 2
Views: 23

acidic vs. basic vs. amphoteric

Hi all!
I was wondering if anyone has any suggestions/easy ways of deciding if an oxide is acidic, basic, or amphoteric.
Thanks!
by paytonm1H
Sun Nov 25, 2018 12:50 pm
Forum: Bond Lengths & Energies
Topic: Bonds in Water
Replies: 5
Views: 35

Bonds in Water

Can someone please explain the difference between the covalent and hydrogen bonds in water? Thanks!
by paytonm1H
Sun Nov 25, 2018 11:17 am
Forum: Dipole Moments
Topic: convention used
Replies: 1
Views: 27

convention used

In the book it says that in the original convention, the electric dipole is represented by an arrow that points towards the negative partial charge, but then continues to say that the book will use the modern convention, where the electric dipole is represented by an arrow that points to the positiv...
by paytonm1H
Thu Nov 22, 2018 4:00 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 1
Views: 53

Expanded Octets

In the textbook, it states that in PCl5, the P atom expands its valence shell to ten electrons by using one d-orbital. Wouldn't the lowest energy be if the P atom used two d-orbitals with the two electrons having the same spin (Hund's Rule)? Why do they only fill one orbital?
Thanks!
by paytonm1H
Mon Nov 12, 2018 7:16 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power
Replies: 5
Views: 48

Re: Polarizing Power

Polarizing power is the ability of a cation to distort an anion. Small cations have the greatest polarizing power because there is a greater concentration of positive charge in a smaller area, attracting the electrons from the anion.
by paytonm1H
Thu Nov 08, 2018 7:04 pm
Forum: Electronegativity
Topic: Covalent Bonds
Replies: 2
Views: 106

Covalent Bonds

Hi all! I'm working on question 2D.7(a), where its asking if AlCl3 or KCl bonds are more covalent. The difference between the electronegativity of AlCl3 is 1.5 and the difference for KCl is 2.2. Since covalent bonds are identified as having a EN difference of <1.5, shouldn't the AlCl3 be considered ...
by paytonm1H
Sat Nov 03, 2018 9:29 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 4197

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

Thank you so much for all your help today Lyndon!! You are incredibly generous with your time! Good luck on your midterms and get well soon!!
by paytonm1H
Thu Nov 01, 2018 9:50 pm
Forum: Ionic & Covalent Bonds
Topic: Copper Ions
Replies: 3
Views: 25

Copper Ions

What is the difference between copper(I) ion and copper(II) ion?
by paytonm1H
Wed Oct 31, 2018 12:42 pm
Forum: Octet Exceptions
Topic: Phosphorus Pentachloride example from class
Replies: 1
Views: 65

Phosphorus Pentachloride example from class

Hi all! In lecture this morning, Dr. Lavelle presented the example of phosphorus pentachloride for expanded valence shells. He wrote that the molecule's ten valence electrons' configuration is s2p6d2, using one d-orbital. Wouldn't the two electrons in the d-orbital occupy two separate orbitals, inst...
by paytonm1H
Mon Oct 29, 2018 7:22 am
Forum: Electronegativity
Topic: Periodic Trends
Replies: 8
Views: 129

Re: Periodic Trends

Electronegativity increases to the right, but this trend does not include the noble gases. So Fluorine has the highest electronegativity, not Ne or He. This makes sense because electronegativity refers to an element's ability to form covalent bonds, and noble gases don't bond.
by paytonm1H
Thu Oct 25, 2018 11:25 pm
Forum: DeBroglie Equation
Topic: momentum of light
Replies: 2
Views: 82

momentum of light

In regards to the DeBroglie equation, can light have momentum even though photons are massless?
Thanks!
by paytonm1H
Thu Oct 25, 2018 8:30 pm
Forum: Einstein Equation
Topic: Calculating number of photons emitted
Replies: 3
Views: 115

Calculating number of photons emitted

Using the Einstein equation, how do you calculate the number of photons emitted from a light source??
Thanks!
by paytonm1H
Sat Oct 20, 2018 12:12 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 4
Views: 113

Re: Orbitals

My TA told us that we will be tested on the following concepts:
wave/particle duality
photoelectric effect
De Brogile's equation
Heisenberg's indeterminacy equation
electromagnetic spectrum

He also said that his test is problem-solving heavy! I do not believe that orbitals will be on this test.
by paytonm1H
Sat Oct 20, 2018 12:09 pm
Forum: Photoelectric Effect
Topic: Significance of the photoelectric effect
Replies: 3
Views: 75

Re: Significance of the photoelectric effect

The photoelectric effect is significant because it showed that light has both wave-like properties and particle-like properties. The finding was that increasing the intensity of the light would not result in electrons being emitted from the metal surface. Instead, you have to increase the frequency/...
by paytonm1H
Sat Oct 20, 2018 11:58 am
Forum: Properties of Light
Topic: Atomic Spectra pre-module quiz
Replies: 1
Views: 27

Atomic Spectra pre-module quiz

Hi all!
I'm looking for some basic clarification on the atomic spectra... what is the difference between atomic absorption and atomic emission spectroscopy and what does each line/wavelength on the spectrum represent?
Thanks!
by paytonm1H
Sat Oct 20, 2018 11:55 am
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 1
Views: 27

Atomic Spectra

Hi all!
Has anyone completed problem 1A.15? How do find the initial and final values of n when given the line observed at 102.6 nm?
Thanks!
by paytonm1H
Sun Oct 14, 2018 10:54 pm
Forum: Photoelectric Effect
Topic: Threshold Energy
Replies: 2
Views: 35

Threshold Energy

Hi all!
Each unique metal surface has its own threshold energy needed to remove an electron... if this threshold isn't met, is the energy of the incoming photon absorbed by the surface? I'm just curious to know where this energy goes (thinking about the conservation of energy).
Thanks!
by paytonm1H
Sun Oct 14, 2018 10:49 pm
Forum: Limiting Reactant Calculations
Topic: Limting Reactant Calculations
Replies: 1
Views: 106

Limting Reactant Calculations

Hi all!
In the post-module assessment for the limiting reactant calculations module, there were two questions that asked you to find the product formed under the criteria of 1 atm and 25 degrees Celsius. Do these change the way we calculate product or can they be disregarded?
Thank you!
by paytonm1H
Sun Oct 14, 2018 10:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 86
Views: 25093

Re: Advice from a Medical Student [ENDORSED]

Thank you so much! It's always encouraging to hear that our hard work will be applicable for many years to come!
by paytonm1H
Sat Oct 06, 2018 11:36 pm
Forum: Significant Figures
Topic: Chemical Structure
Replies: 2
Views: 46

Chemical Structure

Hi all!
Wondering if I should be reviewing chemical structure properties for the upcoming test... do you think there will be questions where we will need to know basic shapes, polarity, and bond type??
Thank you!
by paytonm1H
Sat Oct 06, 2018 11:31 pm
Forum: Molarity, Solutions, Dilutions
Topic: dilutions? [ENDORSED]
Replies: 5
Views: 65

Re: dilutions? [ENDORSED]

m1v1=m2v2 will be your best friend! Also, here is Lavelle's video module on molarity and dilution of a solution!
https://lavelle.chem.ucla.edu/wp-conten ... n.wmv.html
by paytonm1H
Sat Oct 06, 2018 11:28 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 113
Views: 33003

Re: Rusty on High School Chem [ENDORSED]

Does anyone have any recommendations for a review video on how to read the periodic table and what the columns/rows mean??
Thanks!!

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