Search found 64 matches
- 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: 14135
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...
- 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: 450
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.
- Fri Mar 15, 2019 4:57 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs Free Energy of Formation
- Replies: 2
- Views: 478
Re: Gibbs Free Energy of Formation
As far as I am aware, yes!
- 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: 272
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...
- Fri Mar 15, 2019 4:53 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Homogeneous and Heterogeneous
- Replies: 1
- Views: 196
Homogeneous and Heterogeneous
Are either the homogeneous or heterogeneous catalysts included in the rate law?
- Fri Mar 15, 2019 2:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Yekan Final review slides and solutions 0312
- Replies: 8
- Views: 1205
Re: Yekan Final review slides and solutions 0312
How do you find the number of moles and V2, V1 for this problem?
- Thu Mar 14, 2019 11:28 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Endothermic vs. Exothermic Based on K
- Replies: 1
- Views: 256
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?
- 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: 435
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?
- Thu Mar 14, 2019 6:06 pm
- Forum: First Order Reactions
- Topic: Edition 6 15.23
- Replies: 2
- Views: 306
Edition 6 15.23
For part c, isn't it second-order and not first-order? Bc 2A --> B + C ; k = [A]^2 ?
- Thu Mar 14, 2019 5:11 pm
- Forum: Second Order Reactions
- Topic: Third Order Reactions [ENDORSED]
- Replies: 2
- Views: 354
Third Order Reactions [ENDORSED]
How do you find the integrated rate law for rxns with a greater order than two?
- Thu Mar 14, 2019 10:54 am
- Forum: Student Social/Study Group
- Topic: Note Taking
- Replies: 145
- Views: 15032
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...
- Thu Mar 14, 2019 10:31 am
- Forum: Administrative Questions and Class Announcements
- Topic: Yekan Final review slides and solutions 0312
- Replies: 8
- Views: 1205
Re: Yekan Final review slides and solutions 0312
Thank you so much!
- Wed Mar 13, 2019 11:44 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Exothermic Graph
- Replies: 2
- Views: 270
Exothermic Graph
Can somebody explain what this graph is saying? And why is ES higher than S and P?
- Wed Mar 13, 2019 11:37 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: K1 vs K2
- Replies: 2
- Views: 403
K1 vs K2
Why is it that we use K1 instead of K2 to substitute for [intermediate] in rxn mechanism problems like this?
- Wed Mar 13, 2019 9:55 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Monoatomic Gas
- Replies: 3
- Views: 633
Monoatomic Gas
Does a monoatomic ideal gas indicate constant pressure or constant temperature?
- 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: 5255
Re: Week 9 Worksheet (2E,I,K)
For problem 2 part a, shouldn't c = 0 and not 1?
- Tue Mar 12, 2019 9:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Nathan's Review Session Problems + Solutions
- Replies: 1
- Views: 353
Re: Nathan's Review Session Problems + Solutions
Thank you so much!
- Tue Mar 12, 2019 9:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test #2 4b
- Replies: 2
- Views: 305
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...
- Tue Mar 12, 2019 8:34 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium vs. steady-state
- Replies: 4
- Views: 493
Pre-equilibrium vs. steady-state
Under what conditions is it okay to use the pre-equilibrium method and vice versa for steady-state?
- Sat Mar 09, 2019 2:39 pm
- Forum: First Order Reactions
- Topic: Formula 15.23
- Replies: 2
- Views: 332
Formula 15.23
Which formula/concept does this come from? This is problem 15.23 in edition 6
- 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: 340
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?
- Mon Feb 25, 2019 1:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: inert metals
- Replies: 2
- Views: 242
inert metals
What is the significance of the placement of inert metallic components such as Pt?
- Wed Feb 06, 2019 8:39 am
- Forum: Phase Changes & Related Calculations
- Topic: C (gr) ?
- Replies: 2
- Views: 2179
C (gr) ?
In problem 8.67 (Edition 6), the solutions guide has C (gr). What is (gr) and what is the significance of such?
- Mon Feb 04, 2019 4:42 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Irreversible vs. Reversible Expansion
- Replies: 4
- Views: 364
Irreversible vs. Reversible Expansion
Can somebody explain to me the difference between irreversible and reversible expansion?
- 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: 178
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?
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?
- 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: 491
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.
- Sat Jan 19, 2019 3:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 3 Chemistry Community Posts Deadline
- Replies: 2
- Views: 207
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.
- Sat Jan 19, 2019 3:24 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Protonation
- Replies: 1
- Views: 243
Protonation
Can somebody please explain to me the conceptual basis of the percent of protonation or deprotonation? Thanks!
- 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: 142
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?
- Fri Jan 11, 2019 12:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratic Equations
- Replies: 3
- Views: 293
Re: Quadratic Equations
If so, how would it be possible to distinguish which number to use? Or would either answer be accepted?
- Fri Jan 11, 2019 12:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratic Equations
- Replies: 3
- Views: 293
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)?
- Wed Jan 09, 2019 10:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework 11.39 Edition 6
- Replies: 4
- Views: 424
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?
In the solutions guide, it shows that we multiply K1 by K2. Why is that so?
- Sat Dec 08, 2018 8:43 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Bidentate Chelate
- Replies: 1
- Views: 159
Bidentate Chelate
Can a bidentate ligand form a chelate?
- Tue Dec 04, 2018 3:05 pm
- Forum: Bronsted Acids & Bases
- Topic: No proton transfer: E6, 12.9c
- Replies: 1
- Views: 202
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...
- Sun Dec 02, 2018 3:53 pm
- Forum: Naming
- Topic: Order of Ligands
- Replies: 2
- Views: 330
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?
EX. for pentaamminesulfatocobalt(III)chloride,
are [Co(NH3)5(S04)]Cl and [Co(SO4)(NH3)5]Cl the same?
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?
Charge
How do you determine the charge on a ligand/complex anion?
- Tue Nov 27, 2018 8:22 pm
- Forum: Dipole Moments
- Topic: Nonpolar and Dipole Moments?
- Replies: 3
- Views: 311
Re: Nonpolar and Dipole Moments?
I think what I meant was having zero net dipole moment (like if they cancel out).
- Tue Nov 27, 2018 8:16 pm
- Forum: Dipole Moments
- Topic: Nonpolar and Dipole Moments?
- Replies: 3
- Views: 311
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?
- Fri Nov 23, 2018 1:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework for week 9
- Replies: 11
- Views: 1115
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!
- Fri Nov 23, 2018 1:27 pm
- Forum: Hybridization
- Topic: Hybridization Labeling
- Replies: 5
- Views: 622
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
For reference, this is HW question 4.95 from Edition 6; the structure is CH2=CHCHO
- Fri Nov 23, 2018 12:39 pm
- Forum: Lewis Structures
- Topic: Boron
- Replies: 1
- Views: 220
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)
reference: homework question 4.81 in edition 6 (B3N3H6)
- Mon Nov 19, 2018 7:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma vs. Pi Bonds (What's the difference?)
- Replies: 4
- Views: 336
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.
- Mon Nov 19, 2018 7:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma vs. Pi Bonds (What's the difference?)
- Replies: 4
- Views: 336
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...
- Mon Nov 19, 2018 7:04 pm
- Forum: Bond Lengths & Energies
- Topic: Ball and Stick
- Replies: 2
- Views: 1788
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.
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.
- Mon Nov 19, 2018 6:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bold/Dashed Lines in Bonds
- Replies: 4
- Views: 530
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?
- Mon Nov 12, 2018 6:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Noncovalent Interactions
- Replies: 4
- Views: 236
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?
- Mon Nov 12, 2018 5:59 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Electron Distortion
- Replies: 2
- Views: 315
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?
- Mon Nov 12, 2018 5:57 pm
- Forum: Dipole Moments
- Topic: Interaction Potential Energy
- Replies: 3
- Views: 208
Interaction Potential Energy
In the formula Ep is equivalent to (a1*a2)/r^6, what do the alpha and r values represent?
- Sat Nov 03, 2018 11:45 pm
- Forum: Resonance Structures
- Topic: Resonance [ENDORSED]
- Replies: 2
- Views: 233
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.
- Sat Nov 03, 2018 11:40 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization Energy: Oxygen
- Replies: 1
- Views: 86
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?
- Thu Nov 01, 2018 10:00 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Lowest Energy Lewis Structure: N2O
- Replies: 2
- Views: 4198
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)
(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)
- Sun Oct 28, 2018 9:09 pm
- Forum: Student Social/Study Group
- Topic: Midterm
- Replies: 15
- Views: 1481
Re: Midterm
Previous students have told me they are around 8 questions with multiple parts.
- Sun Oct 28, 2018 9:05 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 3d before 4s for Z > 10
- Replies: 3
- Views: 268
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... ?
- Sun Oct 28, 2018 5:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grading
- Replies: 3
- Views: 287
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...
- Fri Oct 19, 2018 12:26 pm
- Forum: DeBroglie Equation
- Topic: Wavelength unit conversion
- Replies: 4
- Views: 407
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.
- Fri Oct 19, 2018 12:24 pm
- Forum: DeBroglie Equation
- Topic: Momentum of protons
- Replies: 2
- Views: 207
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!
Mass of proton = 1.672 622 × 10−27 kg
Electrons, neutrons, and protons have mass, but photons do not.
Hope this helps!
- Fri Oct 19, 2018 12:21 pm
- Forum: Student Social/Study Group
- Topic: Next week's quiz
- Replies: 5
- Views: 642
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...
- Wed Oct 10, 2018 6:57 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Bohr Relation to H-Atom
- Replies: 1
- Views: 58
Bohr Relation to H-Atom
Can somebody explain why for En = -hR/n2, it is only for hydrogen atoms?
- Wed Oct 10, 2018 6:42 pm
- Forum: Einstein Equation
- Topic: Frequency Comparison
- Replies: 1
- Views: 115
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?
- 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: 276
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?
- Thu Oct 04, 2018 11:37 pm
- Forum: Empirical & Molecular Formulas
- Topic: Rounding in Mole Ratios for Empirical Formulas
- Replies: 2
- Views: 1298
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...
- Tue Oct 02, 2018 3:53 pm
- Forum: Limiting Reactant Calculations
- Topic: Homework Question M9
- Replies: 1
- Views: 220
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?
- Sat Sep 29, 2018 2:23 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Post-Module Assessment Q25
- Replies: 1
- Views: 150
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...