Search found 60 matches
- Tue Mar 12, 2019 3:26 pm
- Forum: Student Social/Study Group
- Topic: Studying for the Final
- Replies: 25
- Views: 2582
Re: Studying for the Final
It's also helpful to do the modules and go to office hours!
- Tue Mar 12, 2019 3:22 pm
- Forum: Zero Order Reactions
- Topic: zero order in rate law
- Replies: 7
- Views: 1150
Re: zero order in rate law
You don't need to include it since anything to the zeroth power is equal to one.
- Tue Mar 12, 2019 3:19 pm
- Forum: Ideal Gases
- Topic: units
- Replies: 15
- Views: 1284
Re: units
Although the products and reactants involved in Kp and Kc use units such as molarity and bar, the units cancel out in the end so K is unitless.
- Fri Mar 08, 2019 12:33 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: oxidizing power vs reducing power
- Replies: 3
- Views: 6409
Re: oxidizing power vs reducing power
So the reducing agent will have a high oxidizing power, and the oxidizing agent will have a high reducing power.
- Fri Mar 08, 2019 12:30 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 12
- Views: 1021
Test 2
Can someone please explain why Gibbs free energy for the combustion of a gas used to heat a BBQ at a pool party is negative? Wouldn't it require be a non-spontaneous process for the combustion to occur?
- Fri Mar 08, 2019 12:22 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 4
- Views: 451
Re: Test 2
I think they meant the Van't Hoff equation; it was provided to us on the equation sheet.
- Tue Feb 26, 2019 11:19 pm
- Forum: Ideal Gases
- Topic: atm vs. bar?
- Replies: 25
- Views: 2734
Re: atm vs. bar?
The units can be atm or bar depending on the problem. Note that this will change the value of R.
- Tue Feb 26, 2019 11:17 pm
- Forum: Ideal Gases
- Topic: Q and K
- Replies: 13
- Views: 1219
Re: Q and K
Q is when the reaction is not at equilibrium. K is when the reaction is at equilibrium. Q is compared to K to determine whether the reaction will shift to the left or right due to the Le Chatalier's Principle.
- Tue Feb 26, 2019 11:06 pm
- Forum: Balancing Redox Reactions
- Topic: basic/acidic solutions
- Replies: 5
- Views: 526
basic/acidic solutions
How do we know if a redox reaction is acidic or basic if no H+ or OH- is given?
- Mon Feb 18, 2019 9:47 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q VS. K
- Replies: 13
- Views: 1543
Re: Q VS. K
Both can be calculated the same way. The only difference is that Q is when the reaction is not at equilibrium and K is when the reaction is at equilibrium.
- Mon Feb 18, 2019 9:44 pm
- Forum: Student Social/Study Group
- Topic: Midterms
- Replies: 5
- Views: 525
Re: Midterms
You should be able to ask for regrading. Just let your TA know and he/she should be able to help with that.
- Mon Feb 18, 2019 9:34 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Final exam
- Replies: 8
- Views: 861
Re: Final exam
The final exam should be on Sunday, March 17 at 11:30am-2:30pm
- Fri Feb 15, 2019 2:49 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Liquid and moles
- Replies: 8
- Views: 1071
Re: Liquid and moles
H20 (l) is not included in the equation because water is in a much larger quantity in comparison to the rest of the reactants so the change in its concentration during a reaction is negligible.
- Fri Feb 15, 2019 2:47 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 5
- Views: 466
Re: Gibbs free energy
Also, Dr. Lavelle said in lecture that Gibbs free energy only refers to situations where the system is not at equilibrium, since delta G when the system is at equilibrium is zero.
- Fri Feb 15, 2019 2:46 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Q. 9.47
- Replies: 1
- Views: 225
Q. 9.47
Question 9.47 in the sixth edition says: Initially a sample of ideal gas at 323 K occupies 1.67 L at 4.95 atm. The gas is allowed to expand to 7.33 L by two pathways: (a) isothermal, reversible expansion; (b) isothermal, irreversible free expansion. Calculate deltaS(tot), deltaS(sys), and deltaS(sur...
- Wed Feb 06, 2019 5:01 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Q. 8.27
- Replies: 1
- Views: 280
Q. 8.27
Question 8.27 from the 6th edition says: Calculate the work for each of the following processes beginning with a gas sample in a piston assembly with T = 305 K, P = 1.79 atm, and V = 4.29 L: (a) irreversible expansion against a constant external pressure of 1.00 atm to a final volume of 6.52 L; (b) ...
- Wed Feb 06, 2019 4:50 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Unit for Heat Capacity
- Replies: 2
- Views: 313
Unit for Heat Capacity
Question 8.43 for the 6th edition give the heat capacities of the different states in units of J/mol. Why is this? I thought the definition of heat capacity is the heat required to raise the temperature of an object by one degree. Wouldn't the units have to include degrees celsius or Kelvin?
- Wed Feb 06, 2019 4:30 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: What is q equal to in the second law of thermodynamics?
- Replies: 5
- Views: 681
Re: What is q equal to in the second law of thermodynamics?
The second law of thermodynamics states that delta S=q/T=nRln(V2/V1). So q=nRTln(V2/V1) if you multiply both sides by temperature. I believe the unit for q is Joules.
- Mon Jan 28, 2019 8:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Week 4 Homework
- Replies: 12
- Views: 1163
Re: Week 4 Homework
I believe Week 4 HW should be on the questions in the Thermodynamics section.
- Mon Jan 28, 2019 8:50 pm
- Forum: Ideal Gases
- Topic: pH and pOH
- Replies: 18
- Views: 1786
Re: pH and pOH
Also, when your chemical reaction includes H30+, you are finding the pH, and when it includes OH-, you are finding the pOH. Make sure to use the equation pH+pOH=14 if you are trying to convert between the two.
- Mon Jan 28, 2019 8:42 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Extensive
- Replies: 4
- Views: 440
Re: Extensive
State property is a quantity that is determined by its current state but is not dependent on the path taken to obtain that state (ex: altitude, volume). Extensive property is a property of matter that depends on the amount of substance (ex: heat capacity).
- Mon Jan 21, 2019 9:26 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Table 11.2
- Replies: 1
- Views: 198
Table 11.2
Table 11.2 has two columns of equilibrium constants denoted K and Kc. While the values are similar for the first few equations, it differs in the latter half. Does anyone know the difference between the two?
- Mon Jan 21, 2019 8:02 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: calculating x cubically
- Replies: 2
- Views: 263
Re: calculating x cubically
I don't think we will have to know how to do that for this class. Here's the link that Dr. Lavelle sent out in an email on solving cubics: viewtopic.php?f=49&t=40016
- Mon Jan 21, 2019 7:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pka and ka
- Replies: 1
- Views: 197
Re: Pka and ka
The lower the pKa, the higher the corresponding Ka is, which relates to increasing acid strength (stronger acids).
- Mon Jan 14, 2019 12:20 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Converting Kc to Kp
- Replies: 3
- Views: 602
Converting Kc to Kp
Do we convert Kc to Kp or vice versa the same way we do for converting individual concentrations/partial pressures using P=(n/V)*(RT)?
- Mon Jan 14, 2019 12:15 am
- Forum: Student Social/Study Group
- Topic: New to Lavelle
- Replies: 32
- Views: 5119
Re: New to Lavelle
I personally think going to office hours is also really helpful since it is a good way to get some answers to the questions you might have after doing the homework problems.
- Mon Jan 14, 2019 12:12 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Chemical Equilibrium Pt. 4 Module Q. 14
- Replies: 1
- Views: 562
Chemical Equilibrium Pt. 4 Module Q. 14
14. The two air pollutants SO2 and NO2 can react in the atmosphere as follows: SO2 (g) + NO2 (g) ⇌ SO3 (g) + NO (g) Predict the effect of the following changes to the amount of NO when the reaction above has come to equilibrium in a stainless steel bulb equipped with entrants for chemicals. i. The a...
- Sat Jan 12, 2019 5:22 pm
- Forum: General Science Questions
- Topic: Week 1 Homework
- Replies: 5
- Views: 476
Re: Week 1 Homework
I think we were also allowed to turn in our homework during discussion for Week 1. It should be fine as long as you turned it in by the Friday lecture.
- Sat Jan 12, 2019 5:15 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: partial pressures vs concentrations
- Replies: 4
- Views: 276
Re: partial pressures vs concentrations
If the reactants or products are gases, then you can usually use either Kp or Kc. However, you can only use Kc for reactions involving aqueous solutions.
- Sat Jan 12, 2019 5:13 pm
- Forum: Ideal Gases
- Topic: Pv=nRT [ENDORSED]
- Replies: 12
- Views: 688
Re: Pv=nRT [ENDORSED]
Since there are multiple values of R, make sure the units of the R you are using cancel out/correspond with the other units in the equation.
- Mon Dec 03, 2018 6:00 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: AXE formula
- Replies: 32
- Views: 11968
Re: AXE formula
Yes, the AXE formula can help you draw the shape of the structure, but it will not tell you the elements involved.
- Mon Dec 03, 2018 5:54 pm
- Forum: Hybridization
- Topic: s character
- Replies: 3
- Views: 319
Re: s character
It's essentially saying that the trend for s-character is the inverse of the trend for p-character.
- Mon Dec 03, 2018 5:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 4
- Views: 663
Test 3
Will be get our test 3 back during discussion this week?
- Wed Nov 28, 2018 11:44 am
- Forum: Lewis Structures
- Topic: lewis structure
- Replies: 2
- Views: 175
Re: lewis structure
The triple bond to nitrogen and single bond to chlorine would also be preferable since it satisfies the octet rule for carbon.
- Wed Nov 28, 2018 11:41 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles Preference
- Replies: 2
- Views: 245
Bond Angles Preference
Would it be ok if I wrote the bond angles for 3 bonds pairs and 1 lone pair to be 107.5, and the bond angles for 2 bond pairs and 2 lone pairs to be 104.5? Or would writing "less than 109.5 degree" be preferred?
- Wed Nov 28, 2018 11:38 am
- Forum: Hybridization
- Topic: pi vs sigma
- Replies: 12
- Views: 1147
Re: pi vs sigma
The head of the sigma bonds overlap directly while the pi bonds overlap laterally since they are parallel to each other, so it is easier to break the pi bonds.
- Sat Nov 24, 2018 7:08 pm
- Forum: Bond Lengths & Energies
- Topic: Single, Double, Triple Bond Lengths
- Replies: 5
- Views: 1565
Re: Single, Double, Triple Bond Lengths
This is because the additional bonding of electrons attracts the nuclei of the bonded atoms closer to each other.
- Sat Nov 24, 2018 7:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lewis Structure N2O
- Replies: 4
- Views: 414
Re: Lewis Structure N2O
This rule usually applies to most structures, where the central atom is the element with the lowest ionization energy and least electronegativity.
- Sat Nov 24, 2018 7:00 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi bonds
- Replies: 5
- Views: 371
Re: Sigma and Pi bonds
They might also ask us about the differences between the two types of bonds.
- Sat Nov 17, 2018 10:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Structure
- Replies: 1
- Views: 165
Molecular Structure
If the two lone pairs of Xe in XeF4 are placed opposite each other due to electron repulsion, why is it that the two lone pairs in H20 are placed next to each other?
- Sat Nov 17, 2018 10:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 3
- Replies: 19
- Views: 1268
Re: Test 3
Memorizing them would definitely help you do the problems faster and focus on other parts of the problem.
- Sat Nov 17, 2018 9:40 pm
- Forum: Hybridization
- Topic: Hybridization Notation
- Replies: 2
- Views: 295
Hybridization Notation
Are the notations that we are learning for hybridization only sp,sp2,and sp3?
- Sat Nov 10, 2018 10:33 am
- Forum: Student Social/Study Group
- Topic: Sig Figs on Midterm
- Replies: 13
- Views: 1493
Re: Sig Figs on Midterm
I would stick to the sig figs rules just to be safe.
- Sat Nov 10, 2018 10:31 am
- Forum: Balancing Chemical Reactions
- Topic: Combustion Equation
- Replies: 21
- Views: 2656
Re: Combustion Equation
Sometimes nitrogen can be an added reactant and product of the equation.
- Sat Nov 10, 2018 10:25 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: HW for discussion
- Replies: 9
- Views: 976
Re: HW for discussion
I did the problems after 3.11 since I believe professor Lavelle said we only needed to know the questions up to 3.11 for the midterm test
- Wed Oct 31, 2018 12:44 am
- Forum: Lewis Structures
- Topic: Exception to Octet Rule [ENDORSED]
- Replies: 3
- Views: 322
Re: Exception to Octet Rule [ENDORSED]
Some common elements that have expanded octets are sulfur, phosphorus, silicon, and chlorine.
- Wed Oct 31, 2018 12:29 am
- Forum: Ionic & Covalent Bonds
- Topic: 6th Edition, Question 3.5
- Replies: 3
- Views: 378
Re: 6th Edition, Question 3.5
Chromium and copper are the two main exceptions to electron configuration. For both elements, an electron from 4s subshell is moved to 3d subshell to make a half full 3d (3d^5) for chromium and a full 3d (3d^10) for Copper, since doing so makes the atom more stable. So for this problem, Cu at ground...
- Tue Oct 30, 2018 10:41 pm
- Forum: Hybridization
- Topic: Question 2.43
- Replies: 4
- Views: 480
Question 2.43
When writing out the electron configuration for silver and antimony, why is 4d^10 before 5s when 4d^10 is after 5s in the periodic table?
- Fri Oct 26, 2018 4:38 pm
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 12
- Views: 911
Speed of Light
Can nothing be faster than the speed of light?
- Fri Oct 26, 2018 4:35 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Principal Quantum Number - Periodic Table
- Replies: 2
- Views: 302
Principal Quantum Number - Periodic Table
Why is it that 3d is not on the same level as 3s and 3p on the periodic table?
- Wed Oct 24, 2018 12:43 am
- Forum: Trends in The Periodic Table
- Topic: Test 2
- Replies: 3
- Views: 296
Test 2
Will Test 2 covers all the questions from Ch. 2 since the questions cover electron affinity, atomic radius, ionic radius, ionization energy and the periodic trends? And if not, up to which questions would you say the test covers?
- Tue Oct 16, 2018 11:12 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Atomic Spectra Module Question 44
- Replies: 1
- Views: 146
Atomic Spectra Module Question 44
Can someone help me explain how to do this question? 44. In the hydrogen atomic spectrum, what is the wavelength of light associated with the n = 4 to n = 1 electron transition? What part of the electromagnetic spectrum is this wavelength? Also will we be required to know the electromagnetic spectru...
- Tue Oct 16, 2018 10:57 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Wavelengths
- Replies: 5
- Views: 338
Wavelengths
Can wavelengths have negative values?
- Tue Oct 16, 2018 10:55 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Negative Signs
- Replies: 2
- Views: 226
Negative Signs
What does it mean when the answer from using the equation (E=-hR/n^2+hR/n^2) to find the energy difference between two energy levels in a H-atom comes out to be negative?
- Tue Oct 09, 2018 3:49 pm
- Forum: Properties of Light
- Topic: Exam
- Replies: 7
- Views: 601
Re: Exam
You can also go to the TAs office hours or UA peer learning sessions.
- Tue Oct 09, 2018 3:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 1 Study Plan
- Replies: 6
- Views: 559
Re: Test 1 Study Plan
You still need a new set of 7 problems (from Fundamentals or The Quantum World) by your discussion though, so make sure to finish those before then.
- Tue Oct 09, 2018 2:21 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Question G13 (Sixth Edition)
- Replies: 3
- Views: 390
Question G13 (Sixth Edition)
Can someone please explain how to do G13? It says: "To prepare a fertilizer solution, a florist dilutes 1.0 L of 0.20 m NH4NO3(aq) by adding 3.0 L of water. The florist then adds 100. mL of the diluted solution to each plant. How many moles of nitrogen atoms will each plant receive? Solve this ...
- Fri Oct 05, 2018 1:35 am
- Forum: Limiting Reactant Calculations
- Topic: multiple limiting reactants
- Replies: 9
- Views: 803
Re: multiple limiting reactants
Yea, when I took the online module that had this question, the correct answer was no (there cannot be more than one limiting reactant). This makes sense because if there were two reactants with the same mole ratio, then neither one would limit the other since they were both consumed completely in th...
- Fri Oct 05, 2018 1:29 am
- Forum: Balancing Chemical Reactions
- Topic: Balancing reactions tips
- Replies: 29
- Views: 1988
Re: Balancing reactions tips
Make sure to double check your answer before you move on! Sometimes I make a couple of arithmetic mistakes without knowing, so make sure you check that both sides have the same number of elements.
- Fri Oct 05, 2018 1:24 am
- Forum: Empirical & Molecular Formulas
- Topic: Empirical formula from MPC
- Replies: 3
- Views: 215
Re: Empirical formula from MPC
There are no decimals used in empirical formulas so you would have to divide the moles by the smallest number of moles calculated and round to the nearest whole number. So in this problem, you would use the molar ratio 3 : 4 : 3