Search found 50 matches
- Sun Mar 18, 2018 6:23 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Adiabatic Process
- Replies: 4
- Views: 626
Re: Adiabatic Process
There was a question on the midterm about this if you're looking for an example problem.
- Sun Mar 18, 2018 6:23 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Midterm Number 5
- Replies: 2
- Views: 453
Re: Midterm Number 5
Okay thank you ! I think you're right.
- Sat Mar 17, 2018 3:16 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Midterm Number 5
- Replies: 2
- Views: 453
Midterm Number 5
Hi guys, for the second step in the fifth question on the midterm, it says that the system returns to the original internal energy. How do we know that the original internal energy is positive 158 joules? I understand how to solve for -158 in part a but i don't know how from -158 we get a positive v...
- Sun Mar 11, 2018 8:37 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Dimerization
- Replies: 2
- Views: 360
Re: Dimerization
Dimerization is when two molecules of the same element react with each other !
A + A --> A2
A + A --> A2
- Sun Mar 11, 2018 8:34 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady State Approximation?
- Replies: 2
- Views: 432
- Sun Mar 11, 2018 8:33 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Heterogenous vs homogenous
- Replies: 2
- Views: 383
Re: Heterogenous vs homogenous
Typical reaction examples with a heterogeneous catalyst involve a solid catalyst with the reactants as either liquids or gases. Typically everything will be present as a gas if there is a homogeneous catalyst.
- Sun Mar 04, 2018 7:49 pm
- Forum: First Order Reactions
- Topic: half life
- Replies: 2
- Views: 393
Re: half life
I believe that for orders that we don't need to use the initial concentration for, half life is an intensive property.
- Sun Mar 04, 2018 7:45 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: When forming rate laws do we include solids and liquids?
- Replies: 5
- Views: 9410
Re: When forming rate laws do we include solids and liquids?
The concentration of solids and liquids does not affect the reactant amount at equilibrium so they are disregarded.
- Sun Mar 04, 2018 7:43 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics an thermodynamics
- Replies: 3
- Views: 482
Re: kinetics an thermodynamics
I think that we should know the conceptual relation between thermodynamics and kinetics, however, in the next chapter text there won't be any mathematical questions tying the two together. Kinetics describes the rates of chemical reactions while thermodynamics studies how different forms of energy a...
- Sat Feb 24, 2018 5:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: What other elements could be used besides Pt?
- Replies: 5
- Views: 695
Re: What other elements could be used besides Pt?
I believe Pt is the most common metal to be used.
- Sat Feb 24, 2018 5:16 pm
- Forum: Balancing Redox Reactions
- Topic: 14.1 D
- Replies: 3
- Views: 548
Re: 14.1 D
Before adding half reactions in order to get a final reaction, you have to make sure that there is the same amount of electrons in each half reaction that are being either gained or lost. In order to do that you may have to multiply a half reaction by a certain number, which was done here to get tho...
- Sat Feb 24, 2018 5:10 pm
- Forum: Balancing Redox Reactions
- Topic: Identifying Oxi/Red Agents [ENDORSED]
- Replies: 6
- Views: 992
Re: Identifying Oxi/Red Agents [ENDORSED]
I have the same question. Wouldn't the S be oxidized because it is the only element of the compound that is losing electrons?
- Sat Feb 24, 2018 5:07 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics
- Replies: 5
- Views: 710
Re: kinetics
Kinetics is related to reactivity and thermodynamics is related to stability!
- Mon Feb 19, 2018 2:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell
- Replies: 3
- Views: 416
Re: Galvanic Cell
I think you should indicate there is a salt bridge and also the direction that the electrons are flowing in.
- Mon Feb 19, 2018 2:38 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Number 14.35 vs. Number 14.37
- Replies: 1
- Views: 344
Number 14.35 vs. Number 14.37
Hey guys, I generally do not understand when to flip the sign of the E value of an anode when solving for the Ecell and when not to. In question 35 it does flip the sign of the anode value and in number 37 it doesn't. Can anyone explain why?
- Sat Feb 10, 2018 3:06 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Evaluation 9.3A
- Replies: 2
- Views: 514
Re: Evaluation 9.3A
When something is compressed isothermally, you use the equation qrev/T!
- Sat Feb 10, 2018 2:53 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Problem 9.75
- Replies: 1
- Views: 387
Problem 9.75
Can someone help me understand for this problem how we know that the cis compound will have twelve different orientations and that the trans compound will only have three? Thanks!
- Mon Feb 05, 2018 2:03 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Reactions Given? [ENDORSED]
- Replies: 2
- Views: 432
Re: Redox Reactions Given? [ENDORSED]
I believe that when given a chemical formula, we are expected to determine which elements are being oxidized or reduced, and subsequently write out their half reactions.
- Mon Jan 29, 2018 10:14 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Internal Energy
- Replies: 2
- Views: 419
Re: Internal Energy
Work calculations will be on the second test.
- Mon Jan 29, 2018 10:13 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Positional disorder?
- Replies: 2
- Views: 324
Re: Positional disorder?
They are essentially the same thing !
- Mon Jan 29, 2018 10:12 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Degeneracy and Entropy
- Replies: 3
- Views: 535
Re: Degeneracy and Entropy
Degeneracy is the different number of ways that energy can exist. There is a direct relationship between entropy and the degree of degeneracy, meaning that if there is a high degree of degeneracy, there will be more entropy because there are more configurations of energy to be in.
- Sun Jan 28, 2018 6:25 pm
- Forum: Calculating Work of Expansion
- Topic: Thermodynamics for W
- Replies: 3
- Views: 619
Re: Thermodynamics for W
You use that equation when pressure is not constant. -PdeltaV is used when pressure is constant.
- Sun Jan 28, 2018 6:21 pm
- Forum: Calculating Work of Expansion
- Topic: work done on and by the system
- Replies: 12
- Views: 1353
Re: work done on and by the system
When work is being done by the system, w will be positive. When work is being done on the system, w will be negative.
- Sun Jan 28, 2018 6:18 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Chapter 9 help
- Replies: 3
- Views: 502
- Fri Jan 19, 2018 8:10 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Thermodynamic vocabulary
- Replies: 3
- Views: 709
Re: Thermodynamic vocabulary
Isothermal just means constant temperature ! The temperature inside a system can be the same as its surroundings without it being necessary for the system to be closed.
- Fri Jan 19, 2018 8:04 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Radiation vs. Convection
- Replies: 3
- Views: 412
Re: Radiation vs. Convection
Convection is the transfer of energy by movement of the medium present while radiation is transfer of energy through thermal radiation. Radiation does not require a medium.
- Fri Jan 19, 2018 8:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Energy and matter?
- Replies: 6
- Views: 687
Re: Energy and matter?
Yes they are taken into account for definition purposes however they are not both transferred in each case.
- Fri Jan 12, 2018 2:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: tables in chapter 8
- Replies: 5
- Views: 331
Re: tables in chapter 8
He will provide the information needed, such as the bond enthalpies when calculating delta H.
- Fri Jan 12, 2018 2:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Textbook Question
- Replies: 1
- Views: 223
Re: Textbook Question
In 14A with Lavelle we covered the fundamentals, chapter one - four, part of seventeen, eleven and some of twelve.
- Fri Jan 12, 2018 2:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Question 8.3
- Replies: 2
- Views: 249
Question 8.3
hey guys !
for question 8.3, how do we know that delta V is pi*r^2*d? is it just because we're assuming the bicycle pump is a cylinder ?
for question 8.3, how do we know that delta V is pi*r^2*d? is it just because we're assuming the bicycle pump is a cylinder ?
- Fri Dec 08, 2017 6:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.9
- Replies: 2
- Views: 515
Re: 11.9
I believe that it is just asking you to find coefficients that aren't multiples of smaller numbers.
- Fri Dec 08, 2017 12:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: T-shaped and Trigonal Pyramidal
- Replies: 6
- Views: 808
Re: T-shaped and Trigonal Pyramidal
T shaped have two lone pairs and trigonal pyramidal have one.
- Sun Dec 03, 2017 4:17 pm
- Forum: Coordinate Covalent Bonds
- Topic: Monodentate, Tridentate
- Replies: 1
- Views: 706
Monodentate, Tridentate
I understand the definition of the term monodentate or tridentate but im not really sure how to classify which one applies to a compound when given its name. Could someone help me with the process of figuring that out?
- Sun Dec 03, 2017 4:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Pi and sigma bonds [ENDORSED]
- Replies: 7
- Views: 733
Re: Pi and sigma bonds [ENDORSED]
I think the most important thing to know about pi and sigma bonds is that a single bond is a sigma bond and a double bond is a sigma and a pi bond. Pi bonds don't allow rotation.
- Sun Nov 26, 2017 11:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.9 Problem
- Replies: 4
- Views: 673
Re: 4.9 Problem
It is T shaped because the lone pairs are not taken into account when naming. That means there are three attached atoms.
- Sun Nov 26, 2017 11:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Molecular Shape
- Replies: 3
- Views: 276
Determining Molecular Shape
Hey guys ! I know that in order to find the molecular shape, you have to draw the lewis structure first, but what if there are different resonance structures? How do you know which lewis structure to use for naming?
- Fri Nov 17, 2017 8:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Exceptions to the Octet Rule
- Replies: 4
- Views: 607
Re: Exceptions to the Octet Rule
The elements that can exceed the octet rule and have more than eight electrons are those who have a quantum number of 3 or above!
- Fri Nov 17, 2017 8:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chapter 4
- Replies: 3
- Views: 490
Re: Chapter 4
Yes we've finished chapter four !
- Sun Nov 12, 2017 8:50 pm
- Forum: Lewis Structures
- Topic: Bonding
- Replies: 3
- Views: 530
Re: Bonding
Quadruple bonds usually don't occur because of the octet rule as well. The octet rule would be fulfilled for an element in an ion if there were four bonds which means no other element could be bonded to it. It also would not contribute to a plausible shape for the ion.
- Sun Nov 12, 2017 8:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Resonance
- Replies: 3
- Views: 477
Re: Resonance
Resonance does not influence shape. What configuration to use is determined by using formal charges. The sum of all the formal charges should equate the charge of the ion, or at least be close to it.
- Fri Nov 03, 2017 6:05 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 2
- Views: 386
Re: Orbitals
I agree with Ryan. Just in case, I would specify the subshell.
- Fri Nov 03, 2017 6:00 pm
- Forum: *Shrodinger Equation
- Topic: What does this even mean?
- Replies: 4
- Views: 737
Re: What does this even mean?
Solving Schrodinger's equation helps you find the wavefunctions and energy levels of an electron in an atom. The quantized energies of the system, once calculated, helps you find out other properties of the atom such as its shape and orientation.
- Fri Oct 27, 2017 5:42 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polyatomic Lewis Structures
- Replies: 5
- Views: 1386
Re: Polyatomic Lewis Structures
The polyatomic ions aren't their usual, balanced charge so when something is 3+, it means that it has three less electrons that it would normally. Anions gain electrons and Cations lose them. When you draw lewis structures, people usually write the charge in the upper right to differentiate !
- Fri Oct 27, 2017 5:35 pm
- Forum: Lewis Structures
- Topic: Double or single bonds
- Replies: 4
- Views: 500
Re: Double or single bonds
When drawing a Lewis structure, you have to count the valence electrons of every element and multiply that number by the amount of molecules of that element if that is needed. After you know how many total electrons there are, you can start drawing the structure with, generally, the least electroneg...
- Fri Oct 20, 2017 4:44 pm
- Forum: DeBroglie Equation
- Topic: Conceptual Wavelength measurement
- Replies: 3
- Views: 453
Re: Conceptual Wavelength measurement
I believe that Plank's constant might be the limit.
- Fri Oct 20, 2017 4:39 pm
- Forum: Photoelectric Effect
- Topic: Energy emitted from an Electron [ENDORSED]
- Replies: 4
- Views: 803
Re: Energy emitted from an Electron [ENDORSED]
When using the Rydberg equation in the form of r(1/N1^2 - 1/N2^2), N1 is always the lower energy level! Even if the electron is jumping from a high energy level to a lower one.
- Thu Oct 12, 2017 6:10 pm
- Forum: Properties of Electrons
- Topic: Wave Properties of Electrons
- Replies: 3
- Views: 571
Re: Wave Properties of Electrons
If an electron didn't have wavelike properties, in the photoelectric experiment, the electron would go through the small hole and travel straight. However, because the electron has wavelike properties, it hit several different locations. An example of wavelike properties would be fields oscillating ...
- Thu Oct 12, 2017 6:08 pm
- Forum: Properties of Electrons
- Topic: Rydberg's Equation [ENDORSED]
- Replies: 3
- Views: 341
Rydberg's Equation [ENDORSED]
If an electron, for example, is jumping from n=4 to n=2, do you still use n=2 as the value of n1 in rydberg's equation?
- Thu Oct 05, 2017 7:18 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: E.27 [ENDORSED]
- Replies: 2
- Views: 434
Re: E.27 [ENDORSED]
I did this question by calculating the molar mass of water, and then converting that to molecules using a conversion equation with avogadro's number.
- Thu Oct 05, 2017 7:14 pm
- Forum: Limiting Reactant Calculations
- Topic: Avogadros Number
- Replies: 6
- Views: 1737
Re: Avogadros Number
Avogadro's number will be one of the constants that is supplied on a sheet that we can use on the test but I would suggest memorizing it as well! It will be used throughout the year for different purposes, however for the test tomorrow, it will be used in conversion equations. It represents the numb...