Search found 73 matches
- Sun Mar 18, 2018 2:41 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: cis and trans molecules
- Replies: 3
- Views: 704
Re: cis and trans molecules
In chapter 9 #75, the molecule cis-MX2Y4 has a higher molar entropy than trans-MX2Y4.
- Sat Mar 17, 2018 5:37 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: nernst eqn
- Replies: 1
- Views: 334
Re: nernst eqn
2013 exam*
- Sat Mar 17, 2018 5:26 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: nernst eqn
- Replies: 1
- Views: 334
nernst eqn
E = Eo - RT/nF * ln Q
E = Eo -0.05916 V/n * log Q
In the 2016 final exam #4A, I used the latter equation but the answer key used the first equation. I got roughly the same answer (944V). The answer key said 942V. Would I get marked down for an answer a few volts off?
E = Eo -0.05916 V/n * log Q
In the 2016 final exam #4A, I used the latter equation but the answer key used the first equation. I got roughly the same answer (944V). The answer key said 942V. Would I get marked down for an answer a few volts off?
- Sat Mar 17, 2018 5:00 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: equations
- Replies: 1
- Views: 341
equations
What are the equations of the definitions for the 3 laws of thermodynamics?
For the 2nd law, is it right to say that 2nd law is deltaS(univ) > 0?
For the 1st law, is it delta U univ =0?
For the 2nd law, is it right to say that 2nd law is deltaS(univ) > 0?
For the 1st law, is it delta U univ =0?
- Sat Mar 17, 2018 4:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge and porous disks
- Replies: 1
- Views: 362
salt bridge and porous disks
Do salt bridge/porous disk: does it allow cations to move or do they only allow counter ions such as Cl- to be transferred?
- Sat Mar 17, 2018 4:57 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: cis and trans molecules
- Replies: 3
- Views: 704
cis and trans molecules
Why do cis molecules have a higher molar entropy than trans molecules?
- Sat Mar 17, 2018 1:28 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: units
- Replies: 2
- Views: 402
units
w(max) = deltaG of a voltaic cell, but then the units of w are J and deltaG's units are J/mol. Why is this?
- Sat Mar 17, 2018 1:12 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: acidic/basic
- Replies: 2
- Views: 398
acidic/basic
Whenever a redox equation is acidic or basic, is the H+/OH- ion on the left side of the equation or the right?
- Wed Mar 14, 2018 2:04 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2760057
Re: Post All Chemistry Jokes Here
Practice Exam Problem:
How many views does Chemistry Community have? (10 pts)
a) 100,000
b) 1,000,000
c) 5,000,000
d) none of the above
How many views does Chemistry Community have? (10 pts)
a) 100,000
b) 1,000,000
c) 5,000,000
d) none of the above
- Mon Mar 12, 2018 3:00 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2760057
Re: Post All Chemistry Jokes Here
Is it me or did I stumble into 14C today?
- Mon Mar 12, 2018 2:59 pm
- Forum: *Alcohols
- Topic: study tips
- Replies: 3
- Views: 1872
study tips
Is there any good mnemonic device for memorizing all the functional groups?
- Thu Mar 08, 2018 12:08 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow step
- Replies: 3
- Views: 395
Re: Slow step
The step with the smaller k value.
- Thu Mar 08, 2018 12:07 am
- Forum: First Order Reactions
- Topic: Simpler way to calculate change in concentrations
- Replies: 2
- Views: 362
Re: Simpler way to calculate change in concentrations
No, I wouldn't see a reason why you would be penalized for using that equation. As long as it helps you get the right answer, you're good.
- Thu Mar 08, 2018 12:05 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2760057
Re: Post All Chemistry Jokes Here
me: that midterm was so easy
me: *gets back grade
me: *gets back grade
- Sun Mar 04, 2018 10:14 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: rates of reaction vs rates of consumption and formation (15.3)
- Replies: 3
- Views: 1119
Re: rates of reaction vs rates of consumption and formation (15.3)
I think it's because the rate for consumption is negative[change in concentration]/change in time, and the change in concentration was negative. Thus, the answer was positive.
- Sun Mar 04, 2018 9:53 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: test 2 last Q
- Replies: 3
- Views: 527
test 2 last Q
For those who took the test for 2I, is Q=1?
- Sun Mar 04, 2018 9:53 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: oxidizing power
- Replies: 2
- Views: 359
oxidizing power
How would you rank different reactions' oxidizing power based on their reduction potentials?
- Wed Feb 21, 2018 11:16 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: mistake in Ch 14. #35.b?
- Replies: 1
- Views: 258
mistake in Ch 14. #35.b?
In the solutions manual for #35.b in chapter 14, it uses the half reaction In3+ + 2e- --> In2+, but in the appendix, the half reaction is In3+ + 1e- --> ln 2+. Is this a mistake?
- Wed Feb 21, 2018 10:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E and Eo
- Replies: 2
- Views: 1198
E and Eo
What's the difference between E and Eo?
- Wed Feb 21, 2018 8:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell potential
- Replies: 1
- Views: 356
Cell potential
When cell potential is negative since anode potential is larger than cathode, the reaction does not favor products. Can we assume that the reaction favors reactants then? (chapter 14, #31.b)
- Wed Feb 21, 2018 3:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: #29.c
- Replies: 1
- Views: 204
#29.c
In the cell diagram for chapter 14 #29.c, the cell diagram goes Pt(s) l H2(g) l H+ (aq) ll Fe2+, Fe3+ l Pt(s). Does the order of the iron ions within the brackets matter?
- Wed Feb 21, 2018 12:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: appendix 2
- Replies: 2
- Views: 322
appendix 2
In the back of the textbook, appendix 2, page A18, it says that Fe2+ + e- --> Fe2+. Eo= +0.77V. Isn't the charge of the ion supposed to change?
- Wed Feb 14, 2018 3:23 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: sign of delta S
- Replies: 1
- Views: 308
sign of delta S
When determining the sign of delta S, do you look at only moles of gas on both sides of reaction or can you also look at moles of liquid and solid?
- Wed Feb 14, 2018 2:47 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delta S total and delta G
- Replies: 2
- Views: 1179
delta S total and delta G
How are delta S total and delta G related?
- Wed Feb 14, 2018 12:39 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: stability and +/- delta G
- Replies: 1
- Views: 5557
stability and +/- delta G
On 9.63, it says that whenever deltaG (formation) is negative, it is thermodynamicaly stable. Why is this?
- Wed Feb 14, 2018 12:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta S (molar) versus delta S (formation) [ENDORSED]
- Replies: 1
- Views: 306
delta S (molar) versus delta S (formation) [ENDORSED]
Is there a difference between delta S (molar) and delta S (formation).
- Tue Feb 13, 2018 12:14 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: deltaG and deltaS(sys) at zero
- Replies: 1
- Views: 175
deltaG and deltaS(sys) at zero
A sample of 1 mole of gas initially at 1 atm and 298 K is heated at constant pressure to 350 K, then the gas is compressed isothermally to its initial volume and is then cooled to 298 K at constant volume. Why are deltaS(sys) and deltaG zero in this case? Which equations would you use to figure what...
- Mon Feb 12, 2018 3:07 am
- Forum: Balancing Redox Reactions
- Topic: midterm W18
- Replies: 1
- Views: 249
midterm W18
Will electrochemistry be on the midterm? If so, up to what part?
- Mon Feb 12, 2018 3:05 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Delta S total
- Replies: 1
- Views: 1987
Delta S total
Could someone explain to me how do equilibrium and reversible reactions relevant when answering the question: "Is delta Surrounding = - delta System" ?
This was on Lyndon's practice midterm #3f.
This was on Lyndon's practice midterm #3f.
- Mon Feb 12, 2018 3:03 am
- Forum: Phase Changes & Related Calculations
- Topic: phase change
- Replies: 1
- Views: 177
phase change
How is it possible for H20 gas to stay in that form at 25 Celsius?
- Fri Feb 02, 2018 1:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: enthalpy
- Replies: 1
- Views: 218
enthalpy
What is deltaH when chem community is on fire?
- Fri Feb 02, 2018 1:22 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: reversible and irreversible with entropy
- Replies: 2
- Views: 372
reversible and irreversible with entropy
deltaS= q(rev)/T. Will we ever use q(irrev)to calculate deltaS and if so when?
- Fri Feb 02, 2018 1:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase change
- Replies: 4
- Views: 465
Re: Phase change
Usually when temperature is constant and no chemical reaction is occurring.
- Thu Jan 25, 2018 3:11 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: constant pressure
- Replies: 5
- Views: 475
constant pressure
I understand that at constant pressure, q= delta H, but do you use enthalpy of the reaction or enthalpy of formation?
- Wed Jan 24, 2018 8:23 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: isothermal system
- Replies: 3
- Views: 426
isothermal system
In an isothermal system, if the change in moles is not zero, would delta U still be zero?
- Wed Jan 24, 2018 1:38 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: C at constant V and P [ENDORSED]
- Replies: 1
- Views: 150
C at constant V and P [ENDORSED]
Why is it that at constant pressure C= delta H/ delta T but at constant volume C = delta U/ delta T?
- Tue Jan 23, 2018 10:24 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 8.25
- Replies: 1
- Views: 170
8.25
Could someone explain this problem to me? A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q 3.50 kJ), resulting in a temperature rise of 7.32 C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(a...
- Tue Jan 23, 2018 9:08 pm
- Forum: Calculating Work of Expansion
- Topic: reversible and irreversible
- Replies: 2
- Views: 306
reversible and irreversible
Conceptually what's the difference between reversible and irreversible processes?
- Tue Jan 23, 2018 3:44 pm
- Forum: Calculating Work of Expansion
- Topic: reversible and irreversible [ENDORSED]
- Replies: 1
- Views: 154
reversible and irreversible [ENDORSED]
Conceptually what's the difference between reversible and irreversible processes?
- Sun Jan 21, 2018 8:00 pm
- Forum: Phase Changes & Related Calculations
- Topic: Irreversible and Reversible
- Replies: 7
- Views: 681
Re: Irreversible and Reversible
Questions about both reversible and irreversible have been on the homework, so it's safe to assume that they may be on the test.
- Sun Jan 21, 2018 8:00 pm
- Forum: Calculating Work of Expansion
- Topic: What do these variables mean?
- Replies: 4
- Views: 447
Re: What do these variables mean?
Yep! P is pressure too.
- Fri Jan 19, 2018 3:39 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: atm*L to J
- Replies: 1
- Views: 870
atm*L to J
When calculating work, when do you multiple -PdeltaV by 101.325 J/(atm*L) versus multiplying by (8.314 J*K*mol-1)/(0.08206L*atm*K-1*mol-1)?
- Fri Jan 12, 2018 1:04 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy Change Signs
- Replies: 5
- Views: 1371
Re: Enthalpy Change Signs
Yes there's a sign change, because the reaction would change from endo to exothermic or vice versa.
- Fri Jan 12, 2018 1:03 pm
- Forum: Phase Changes & Related Calculations
- Topic: ∆Hsub= ∆Hfus+ ∆Hvap
- Replies: 4
- Views: 3247
Re: ∆Hsub= ∆Hfus+ ∆Hvap
Sublimation is the phase change from solid to gas, and vaporization is the phase change from liquid to gas and fusion is the phase change from slid to liquid.
- Fri Jan 12, 2018 1:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Times to post per week
- Replies: 5
- Views: 704
Re: Times to post per week
Yeah it's 3 times.
- Sun Dec 10, 2017 4:08 pm
- Forum: Einstein Equation
- Topic: Einstein Constant [ENDORSED]
- Replies: 1
- Views: 375
Re: Einstein Constant [ENDORSED]
Einstein constant is a cosmological constant that Einstein used to describe general relativity. It is not the inverse of the planck's constant.
- Sun Dec 10, 2017 4:04 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: HClO [ENDORSED]
- Replies: 1
- Views: 541
Re: HClO [ENDORSED]
No, it is not. HClO4 and HCl are strong acids.
- Sun Dec 10, 2017 4:02 pm
- Forum: Biological Examples
- Topic: Hemoglobin
- Replies: 5
- Views: 1005
Re: Hemoglobin
myoglobin and Fe. It is used to transport O2 molecules
- Sun Dec 10, 2017 4:00 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2760057
- Sun Dec 10, 2017 12:15 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Cl -2
- Replies: 2
- Views: 425
Cl -2
Why is the electron configuration for Cl -2 [Ne] 3s^2 3p^6 4s^1 and not [Ar]4s^1?
- Sat Dec 09, 2017 9:44 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: titration
- Replies: 3
- Views: 264
titration
Is any knowledge of titration required on the final?
- Fri Dec 08, 2017 9:47 pm
- Forum: Conjugate Acids & Bases
- Topic: naming [ENDORSED]
- Replies: 1
- Views: 296
naming [ENDORSED]
Do we have to know how to name acids and bases?
- Fri Dec 08, 2017 7:36 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 12.33 part c
- Replies: 1
- Views: 201
Re: 12.33 part c
It's probably a typo. I think it meant concentration.
- Fri Dec 08, 2017 7:32 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH vs pOH
- Replies: 2
- Views: 551
Re: pH vs pOH
pH is equal to 14-pOH. pH can be calculated from concentration of H3O+ and pOH is calculated from concentration of OH-.
- Fri Dec 08, 2017 7:31 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2760057
Re: Post All Chemistry Jokes Here
What was the combustion reaction for the skirball fire?
- Tue Nov 28, 2017 8:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K constant
- Replies: 2
- Views: 352
K constant
Let's say there is a chemical equation that involves a gas and an aqueous solution. If the questions asks for K, do you include only gas, only concentration, or both?
- Tue Nov 28, 2017 8:16 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: coordination compounds
- Replies: 1
- Views: 275
coordination compounds
How do you know the number of bonds a central metal atom has in a coordination compound?
- Wed Nov 22, 2017 4:31 pm
- Forum: Hybridization
- Topic: Hypervalent Hybridization
- Replies: 2
- Views: 404
Re: Hypervalent Hybridization
The hybridization of a sulfate ion would be sp3. You can picture it like it's Ch4 as if it's a tetrahedral. Hope this answered your question.
- Wed Nov 22, 2017 4:27 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Determine the Charge on Ligands
- Replies: 4
- Views: 7846
Re: Determine the Charge on Ligands
You would determine the charge on coordination compounds by comparing the charges of the ligands, which are given in a table on professor Lavelle's website. The charge of the metal/central atom can be given by the name of the compound. (ex: (IV)) By combining all the charges of the central atom and ...
- Sun Nov 19, 2017 9:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 180degrees and lone pairs?
- Replies: 4
- Views: 588
Re: 180degrees and lone pairs?
The molecule may have an electron configuration of a square planar.
- Sun Nov 19, 2017 9:30 pm
- Forum: Biological Examples
- Topic: Cobalt
- Replies: 4
- Views: 562
Re: Cobalt
It is also important for the production of red blood cells and myelin sheath.
- Sun Nov 19, 2017 9:21 pm
- Forum: Biological Examples
- Topic: hemoglobins
- Replies: 1
- Views: 362
hemoglobins
Can someone explain the structure of hemoglobins and how they bind and disconnect oxygenatoms?
- Sun Nov 19, 2017 9:19 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Difference Between Sigma and Pi Bonds [ENDORSED]
- Replies: 4
- Views: 1209
Re: Difference Between Sigma and Pi Bonds [ENDORSED]
You can think of sigma bonds connecting atoms directly along the x-axis while pi bonds connect the two atoms between the top and bottom of the y-axis of atoms.
- Sun Nov 05, 2017 10:16 pm
- Forum: Dipole Moments
- Topic: S+ and S- Dipole Moment
- Replies: 4
- Views: 10877
Re: S+ and S- Dipole Moment
S+ usually refers to the atom which lost an electron while S- refers to the atom that gained an electron.
- Sun Nov 05, 2017 10:14 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: electron density
- Replies: 3
- Views: 475
electron density
What is the definition of electron density?
- Sun Oct 29, 2017 10:59 pm
- Forum: Resonance Structures
- Topic: Resonance Structures [ENDORSED]
- Replies: 3
- Views: 525
Re: Resonance Structures [ENDORSED]
You draw a resonance structure by drawing all the possible structures and arrows that show that the molecule oscillate between the different lewis diagrams.
- Sun Oct 29, 2017 10:58 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: d and s blocks
- Replies: 16
- Views: 2063
Re: d and s blocks
S blocks are written before d blocks always, unless the n value of s is equal or higher than the n value of d.
- Tue Oct 17, 2017 6:20 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Formula
- Replies: 2
- Views: 314
Rydberg Formula
The equation in the book uses the formula: frequency = R(1/n^2 - 1/N^2)
However, when I google the formula, it is 1/wavelength = R(1/n^2 - 1/N^2).
Why is that?
However, when I google the formula, it is 1/wavelength = R(1/n^2 - 1/N^2).
Why is that?
- Tue Oct 17, 2017 6:16 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Question 1.15
- Replies: 6
- Views: 469
Re: Question 1.15
This is because in the formula v= R(1/n^2 - 1/N^2), if n was 3 and N was 1, the frequency would be a negative number.
1/9 - 1/1 = negative number.
1/9 - 1/1 = negative number.
- Fri Oct 13, 2017 2:44 pm
- Forum: Photoelectric Effect
- Topic: What is the extent of elements for the photoelectric effect?
- Replies: 2
- Views: 352
Re: What is the extent of elements for the photoelectric effect?
Non metals are not likely to exhibit any photoelectric effect, because only metals have 'spare' electrons available in their outer shells.
- Fri Oct 13, 2017 2:42 pm
- Forum: Photoelectric Effect
- Topic: Post-Assessment #16
- Replies: 1
- Views: 170
Re: Post-Assessment #16
The answer is threshold energy.
- Fri Oct 06, 2017 2:16 am
- Forum: SI Units, Unit Conversions
- Topic: Significant Figures [ENDORSED]
- Replies: 9
- Views: 2041
Re: Significant Figures [ENDORSED]
For multiplication and division, the least number of significant figures in any number of the problem determines the number of significant figures in the answer. For example 4.00 x 3.0 = 12 Since the number with the least sig figs in the problem is "3.0", which has 2 sig figs, the answer h...
- Fri Oct 06, 2017 2:08 am
- Forum: Limiting Reactant Calculations
- Topic: Exercise M.11 [ENDORSED]
- Replies: 3
- Views: 655
Re: Exercise M.11 [ENDORSED]
Yes, that is correct. To answer this question in simpler terms, you take the excess moles of oxygen left over from the first reaction, and use that value to calculate the number of moles of P4O10 formed. Then, you use the moles of P4O6 formed from the first reaction to find the moles of P4O10 formed...