Search found 64 matches

by Christine Chen 1H
Fri Mar 15, 2019 5:06 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: using q=n(deltaH) vs q=mc(deltaT)
Replies: 4
Views: 141

Re: using q=n(deltaH) vs q=mc(deltaT)

Hey! The reason we use q=n(deltaH) for ice is because it is changing phases from a solid to liquid, but the temperature of ice is not changing since 0 degrees Celsius is the freezing point. q=mc(deltaT) is used to calculate the heat required for a temperature change, which in this case, water change...
by Christine Chen 1H
Fri Mar 15, 2019 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.63
Replies: 1
Views: 85

Re: Question 8.63

Hey! To atomize means to break down into smaller parts. Since C(gr) does not have a bond with another element, it is atomized instead of bonds being broken or formed.
by Christine Chen 1H
Fri Mar 15, 2019 4:57 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs Free Energy of Formation
Replies: 2
Views: 80

Re: Gibbs Free Energy of Formation

As far as I am aware, yes!
by Christine Chen 1H
Fri Mar 15, 2019 4:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Lecture Cell Diagram Example
Replies: 3
Views: 41

Re: Lecture Cell Diagram Example

Hey! Essentially, we put the single bar (I) to distinguish different phases (solid, gas, liquid, aqueous) from each other. Even though both Ag and AgBr are both solids, they are technically different phases because solids cannot mix with each other, so they are considered to be in separate phases. H...
by Christine Chen 1H
Fri Mar 15, 2019 4:53 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homogeneous and Heterogeneous
Replies: 1
Views: 28

Homogeneous and Heterogeneous

Are either the homogeneous or heterogeneous catalysts included in the rate law?
by Christine Chen 1H
Fri Mar 15, 2019 2:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Yekan Final review slides and solutions 0312
Replies: 8
Views: 361

Re: Yekan Final review slides and solutions 0312

How do you find the number of moles and V2, V1 for this problem?
by Christine Chen 1H
Thu Mar 14, 2019 11:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Endothermic vs. Exothermic Based on K
Replies: 1
Views: 30

Endothermic vs. Exothermic Based on K

For questions similar to part B of this problem, how do you determine whether a reaction is endothermic or exothermic based on their reaction profile?
by Christine Chen 1H
Thu Mar 14, 2019 6:24 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Key Words indicating Cp vs Cv [ENDORSED]
Replies: 1
Views: 111

Key Words indicating Cp vs Cv [ENDORSED]

When do we use Cp vs Cv? Are there key words in a problem that may indicate that we use one over the other?
by Christine Chen 1H
Thu Mar 14, 2019 6:06 pm
Forum: First Order Reactions
Topic: Edition 6 15.23
Replies: 2
Views: 52

Edition 6 15.23

For part c, isn't it second-order and not first-order? Bc 2A --> B + C ; k = [A]^2 ?
by Christine Chen 1H
Thu Mar 14, 2019 5:11 pm
Forum: Second Order Reactions
Topic: Third Order Reactions [ENDORSED]
Replies: 2
Views: 73

Third Order Reactions [ENDORSED]

How do you find the integrated rate law for rxns with a greater order than two?
by Christine Chen 1H
Thu Mar 14, 2019 10:54 am
Forum: Student Social/Study Group
Topic: Note Taking
Replies: 32
Views: 1481

Re: Note Taking

Personally, I take notes on my laptop with Microsoft OneNote. I think that it's a lot better than Google Docs bc there are a lot of font options and it's more flexible/note-friendly. To study, I often rewrite my notes so that I fully understand the concepts and redo the problems from lectures. If yo...
by Christine Chen 1H
Wed Mar 13, 2019 11:44 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Exothermic Graph
Replies: 2
Views: 55

Exothermic Graph

Can somebody explain what this graph is saying? And why is ES higher than S and P?
by Christine Chen 1H
Wed Mar 13, 2019 11:37 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: K1 vs K2
Replies: 2
Views: 53

K1 vs K2

Why is it that we use K1 instead of K2 to substitute for [intermediate] in rxn mechanism problems like this?
by Christine Chen 1H
Wed Mar 13, 2019 9:55 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Monoatomic Gas
Replies: 3
Views: 117

Monoatomic Gas

Does a monoatomic ideal gas indicate constant pressure or constant temperature?
by Christine Chen 1H
Wed Mar 13, 2019 4:10 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 913

Re: Week 9 Worksheet (2E,I,K)

For problem 2 part a, shouldn't c = 0 and not 1?
by Christine Chen 1H
Tue Mar 12, 2019 9:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test #2 4b
Replies: 2
Views: 47

Re: Test #2 4b

Hey! I think it's because H+ and the other ions contribute to charge difference and therefore, electron balance. H2O doesn't really do much because it is neutral and doesn't contribute to electron balance and the oxidation number of either element doesn't change from one side of the reaction to anot...
by Christine Chen 1H
Tue Mar 12, 2019 8:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equilibrium vs. steady-state
Replies: 4
Views: 48

Pre-equilibrium vs. steady-state

Under what conditions is it okay to use the pre-equilibrium method and vice versa for steady-state?
by Christine Chen 1H
Sat Mar 09, 2019 2:39 pm
Forum: First Order Reactions
Topic: Formula 15.23
Replies: 2
Views: 35

Formula 15.23


Which formula/concept does this come from? This is problem 15.23 in edition 6
by Christine Chen 1H
Sat Mar 09, 2019 1:05 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.17 6th Ed
Replies: 2
Views: 34

15.17 6th Ed

Why is it okay to compare the initial concentration of [C] in experiments 2 and 3 even if the concentrations of [B] are not exactly the same? I thought all other concentrations had to be held constant?
by Christine Chen 1H
Mon Feb 25, 2019 1:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert metals
Replies: 2
Views: 32

inert metals

What is the significance of the placement of inert metallic components such as Pt?
by Christine Chen 1H
Wed Feb 06, 2019 8:39 am
Forum: Phase Changes & Related Calculations
Topic: C (gr) ?
Replies: 2
Views: 48

C (gr) ?

In problem 8.67 (Edition 6), the solutions guide has C (gr). What is (gr) and what is the significance of such?
by Christine Chen 1H
Mon Feb 04, 2019 4:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Irreversible vs. Reversible Expansion
Replies: 4
Views: 82

Irreversible vs. Reversible Expansion

Can somebody explain to me the difference between irreversible and reversible expansion?
by Christine Chen 1H
Sun Jan 20, 2019 12:57 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Edition 6 12.69 Part b
Replies: 1
Views: 39

Edition 6 12.69 Part b

The question is as follows: calculate the pH of each of the following solutions (b) 0.055 M AlCl3(aq).
In the solutions manual, the reaction reads: Al(H2O)6^3+ (aq) + H2O(l) --> H3O+(aq) + Al(H2O)5OH^2+ (aq).
Can somebody explain where the H2O comes from?
by Christine Chen 1H
Sat Jan 19, 2019 3:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: exothermic/endothermic
Replies: 3
Views: 89

Re: exothermic/endothermic

Often times, delta H will be given to determine whether a rxn is endothermic or exothermic. Positive delta H = endothermic; Negative delta H = exothermic.
by Christine Chen 1H
Sat Jan 19, 2019 3:26 pm
Forum: Administrative Questions and Class Announcements
Topic: 3 Chemistry Community Posts Deadline
Replies: 2
Views: 45

Re: 3 Chemistry Community Posts Deadline

3 posts a week is a general gauge so you can keep yourself accountable to consistently posting, but as long as you post 30 posts by the end of the quarter, you should receive full credit.
by Christine Chen 1H
Sat Jan 19, 2019 3:24 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Protonation
Replies: 1
Views: 42

Protonation

Can somebody please explain to me the conceptual basis of the percent of protonation or deprotonation? Thanks!
by Christine Chen 1H
Sun Jan 13, 2019 2:31 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Volume Given Equal Moles
Replies: 2
Views: 33

Effect of Volume Given Equal Moles

Where does the reaction shift when the volume decreases and the number of moles of gas are equal on both the reactant and product sides?
by Christine Chen 1H
Fri Jan 11, 2019 12:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic Equations
Replies: 3
Views: 51

Re: Quadratic Equations

If so, how would it be possible to distinguish which number to use? Or would either answer be accepted?
by Christine Chen 1H
Fri Jan 11, 2019 12:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic Equations
Replies: 3
Views: 51

Quadratic Equations

Will there ever be an instance where both factors of the quadratic equation are possible answers for X, the equilibrium concentration (solutions with positive values or values that are smaller than initial reactant concentration)?
by Christine Chen 1H
Wed Jan 09, 2019 10:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 11.39 Edition 6
Replies: 4
Views: 99

Homework 11.39 Edition 6

"Use the information in Table 11.2 to determine the value of K at 500K for the reaction 2NH3(g) + 3Br2(g) --><-- Br2(g) + 2HCl(g)."

In the solutions guide, it shows that we multiply K1 by K2. Why is that so?
by Christine Chen 1H
Sat Dec 08, 2018 8:43 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Bidentate Chelate
Replies: 1
Views: 42

Bidentate Chelate

Can a bidentate ligand form a chelate?
by Christine Chen 1H
Tue Dec 04, 2018 3:05 pm
Forum: Bronsted Acids & Bases
Topic: No proton transfer: E6, 12.9c
Replies: 1
Views: 40

No proton transfer: E6, 12.9c

Can somebody explain to me why the answer is: no protons transfer? 12.9(c) Which of the following reactions can be classified as reactions between Brønsted acids and bases? For those that can be so classified, identify the acid and the base. (Hint: It may help to write the net ionic equations.) CH3C...
by Christine Chen 1H
Sun Dec 02, 2018 3:53 pm
Forum: Naming
Topic: Order of Ligands
Replies: 2
Views: 70

Order of Ligands

When writing the formula for a coordination complex, does the order of the ligands matter?

EX. for pentaamminesulfatocobalt(III)chloride,
are [Co(NH3)5(S04)]Cl and [Co(SO4)(NH3)5]Cl the same?
by Christine Chen 1H
Sat Dec 01, 2018 11:25 pm
Forum: Naming
Topic: Aqua
Replies: 2
Views: 45

Aqua

In the textbook, it says that aqua is OH2 whereas on Professor Lavelle's document aqua is H2O. Why is that and should we just stick with Lavelle's doc?
by Christine Chen 1H
Sat Dec 01, 2018 10:47 pm
Forum: Naming
Topic: Charge
Replies: 1
Views: 34

Charge

How do you determine the charge on a ligand/complex anion?
by Christine Chen 1H
Tue Nov 27, 2018 8:22 pm
Forum: Dipole Moments
Topic: Nonpolar and Dipole Moments?
Replies: 3
Views: 62

Re: Nonpolar and Dipole Moments?

I think what I meant was having zero net dipole moment (like if they cancel out).
by Christine Chen 1H
Tue Nov 27, 2018 8:16 pm
Forum: Dipole Moments
Topic: Nonpolar and Dipole Moments?
Replies: 3
Views: 62

Nonpolar and Dipole Moments?

If a molecule is nonpolar, it can still possibly have dipole moments there will just be no electric dipole moment right?
by Christine Chen 1H
Fri Nov 23, 2018 1:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework for week 9
Replies: 11
Views: 218

Re: Homework for week 9

It probably depends on what your TA wants, but I'm pretty sure that turning in 14 problems under one homework set is fine!
by Christine Chen 1H
Fri Nov 23, 2018 1:27 pm
Forum: Hybridization
Topic: Hybridization Labeling
Replies: 5
Views: 106

Hybridization Labeling

Can somebody explain to me what the labeling of the hybridization (the stuff in parentheses) signifies?
For reference, this is HW question 4.95 from Edition 6; the structure is CH2=CHCHO
by Christine Chen 1H
Fri Nov 23, 2018 12:39 pm
Forum: Lewis Structures
Topic: Boron
Replies: 1
Views: 43

Boron

Why is Boron able to have 4 bonds even though it is a group 13 element?
reference: homework question 4.81 in edition 6 (B3N3H6)
by Christine Chen 1H
Mon Nov 19, 2018 7:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma vs. Pi Bonds (What's the difference?)
Replies: 4
Views: 70

Re: Sigma vs. Pi Bonds (What's the difference?)

Also, sigma bonds are stronger than pi bonds because the electron density is spread out over a greater area and the end-to-end axial overlap of electrons attracts the nuclei to form a strong bond.
by Christine Chen 1H
Mon Nov 19, 2018 7:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma vs. Pi Bonds (What's the difference?)
Replies: 4
Views: 70

Re: Sigma vs. Pi Bonds (What's the difference?)

Hello there! Sigma bonds contain two orbitals, each with one electron, that interact end-to-end to form one bond. Sigma bonds ALLOW bound atoms to rotate, resulting in a sigma bond that has electron density with cylindrical symmetry around the internuclear axis. Pi bonds consist of two orbitals, eac...
by Christine Chen 1H
Mon Nov 19, 2018 7:04 pm
Forum: Bond Lengths & Energies
Topic: Ball and Stick
Replies: 2
Views: 82

Re: Ball and Stick

Hello!
The difference in bond angles is determined by multiple factors. It is determined by the symmetry of a molecule and the electron arrangement of a molecule (number of lone pairs/bonds). The values that you see in the textbook are experimentally tested through spectroscopy and x-ray diffraction.
by Christine Chen 1H
Mon Nov 19, 2018 6:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bold/Dashed Lines in Bonds
Replies: 4
Views: 66

Bold/Dashed Lines in Bonds

In the answer key for the homework, a lot of the Lewis structures bonds have dashed lines/bold lines. What do those lines distinguish and will we need to draw structures in that way on future tests?
by Christine Chen 1H
Mon Nov 12, 2018 6:03 pm
Forum: Ionic & Covalent Bonds
Topic: Noncovalent Interactions
Replies: 4
Views: 85

Noncovalent Interactions

Can somebody confirm my understanding of the following concept: stability and boiling point increase as the number of noncovalent interactions increase? Are there any additional variables that change?
by Christine Chen 1H
Mon Nov 12, 2018 5:59 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron Distortion
Replies: 2
Views: 56

Electron Distortion

I understand that electrons in an atom or molecule cause electron distortion in nearby atoms or molecules, but what exactly does electron distortion entail? Is there a measurable variable for it?
by Christine Chen 1H
Mon Nov 12, 2018 5:57 pm
Forum: Dipole Moments
Topic: Interaction Potential Energy
Replies: 3
Views: 52

Interaction Potential Energy

In the formula Ep is equivalent to (a1*a2)/r^6, what do the alpha and r values represent?
by Christine Chen 1H
Sat Nov 03, 2018 11:45 pm
Forum: Resonance Structures
Topic: Resonance [ENDORSED]
Replies: 2
Views: 72

Re: Resonance [ENDORSED]

Because resonance allows for delocalization, in which the overall energy of a molecule is lowered since its electrons occupy a greater volume, molecules that experience resonance are more stable than those that do not.
by Christine Chen 1H
Sat Nov 03, 2018 11:40 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy: Oxygen
Replies: 1
Views: 38

Ionization Energy: Oxygen

Can somebody explain to me why the ionization energy of oxygen is less than nitrogen despite oxygen being further right on the periodic table?
by Christine Chen 1H
Thu Nov 01, 2018 10:00 am
Forum: Formal Charge and Oxidation Numbers
Topic: Lowest Energy Lewis Structure: N2O
Replies: 2
Views: 237

Lowest Energy Lewis Structure: N2O

In the case of N2O, which resonance structure would be considered the one with the lowest energy and why?
(one structure has -1 for O; +1 for N; 0 for N... another structure has O for N, +1 for O, and +1 for N)
by Christine Chen 1H
Sun Oct 28, 2018 9:09 pm
Forum: Student Social/Study Group
Topic: Midterm
Replies: 15
Views: 372

Re: Midterm

Previous students have told me they are around 8 questions with multiple parts.
by Christine Chen 1H
Sun Oct 28, 2018 9:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d before 4s for Z > 10
Replies: 3
Views: 74

3d before 4s for Z > 10

For clarification, when Z (atomic number) > 10, 3d comes before 4s, 4d comes before 5s, 5d comes before 6s, etc... ?
by Christine Chen 1H
Sun Oct 28, 2018 5:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Grading
Replies: 3
Views: 116

Re: Grading

1) You can check your grade via CCLE. Click on the down arrow next to your name, and click on the "Grades" tab. However, for chem, I believe they do not update grades until the end, so grades are not available yet online. I would discuss further with your TA if you want more information on...
by Christine Chen 1H
Fri Oct 19, 2018 12:26 pm
Forum: DeBroglie Equation
Topic: Wavelength unit conversion
Replies: 4
Views: 83

Re: Wavelength unit conversion

Mass needs to be in kg to cancel out! The only time you would use grams is for molar mass conversions. Other than that, use kg.
by Christine Chen 1H
Fri Oct 19, 2018 12:24 pm
Forum: DeBroglie Equation
Topic: Momentum of protons
Replies: 2
Views: 50

Re: Momentum of protons

Protons actually do have mass!
Mass of proton = 1.672 622 × 10−27 kg
Electrons, neutrons, and protons have mass, but photons do not.
Hope this helps!
by Christine Chen 1H
Fri Oct 19, 2018 12:21 pm
Forum: Student Social/Study Group
Topic: Next week's quiz
Replies: 5
Views: 169

Re: Next week's quiz

My TA said the topics for next week's quiz include photoelectric effect, De Broglie wavelength, Heisenberg's uncertainty principle, atomic spectra, and quantum numbers, so I don't think the quiz will cover atomic orbitals (although it doesn't hurt to memorize the l-values associated with each orbita...
by Christine Chen 1H
Wed Oct 10, 2018 6:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Relation to H-Atom
Replies: 1
Views: 24

Bohr Relation to H-Atom

Can somebody explain why for En = -hR/n2, it is only for hydrogen atoms?
by Christine Chen 1H
Wed Oct 10, 2018 6:42 pm
Forum: Einstein Equation
Topic: Frequency Comparison
Replies: 1
Views: 66

Frequency Comparison

Can somebody explain why in graph 1.17 of edition 6, Na has a greater frequency of radiation (v) than K and Rb? What properties of an element cause the frequency to be higher?
by Christine Chen 1H
Wed Oct 10, 2018 6:34 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Distinguishing the Balmer and Lyman Series
Replies: 1
Views: 48

Distinguishing the Balmer and Lyman Series

Can somebody please distinguish the difference between the balmer and lyman series, and explain the relevance of the difference to the electron's release of energy?
by Christine Chen 1H
Thu Oct 04, 2018 11:37 pm
Forum: Empirical & Molecular Formulas
Topic: Rounding in Mole Ratios for Empirical Formulas
Replies: 2
Views: 72

Rounding in Mole Ratios for Empirical Formulas

When multiplying by an integer to get a whole number for the mole ratio in an empirical formula, do you round the other numbers before multiplying them also? Or do you keep the unrounded number and multiply it by the same integer? Ex. If the ratio for C is 1, H is 9.77, and O is 5.56, you multiply 2...
by Christine Chen 1H
Tue Oct 02, 2018 3:53 pm
Forum: Limiting Reactant Calculations
Topic: Homework Question M9
Replies: 1
Views: 85

Homework Question M9

Part a of question M.9 asks for the net ionic equation for the reaction. How does the net ionic equation differ from a molecular equation?
by Christine Chen 1H
Sat Sep 29, 2018 2:23 pm
Forum: Molarity, Solutions, Dilutions
Topic: Post-Module Assessment Q25
Replies: 1
Views: 62

Post-Module Assessment Q25

25. 5.00 g of KMnO4 is dissolved in a 150.00 mL flask of water. If 20.00 mL of this solution is removed and placed in a new 2nd 250.00 mL flask and filled with water, what is the concentration of the solution in the 2nd flask? Molar Masses: K (39.10 g/mol), Mn (54.94 g/mol), O (16.00 g/mol) Why is M...

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