Search found 169 matches
- Sat Mar 17, 2018 10:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrodes
- Replies: 3
- Views: 615
Re: Electrodes
When there is no solid metal in a reaction, add Pt(s).
- Sat Mar 17, 2018 10:49 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Adiabatic vs Isothermal
- Replies: 5
- Views: 2325
Re: Adiabatic vs Isothermal
Adiabatic is when there is no transfer of heat. Iso thermal is when the change in internal energy is 0.
- Sat Mar 17, 2018 10:46 pm
- Forum: *Ketones
- Topic: Keytone and Aldeyhdes
- Replies: 3
- Views: 3308
Re: Keytone and Aldeyhdes
Aldehyde is on the end and ketone is in the middle.
- Sat Mar 17, 2018 2:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram: Porous Disk and Salt Bridge
- Replies: 5
- Views: 2086
Re: Cell Diagram: Porous Disk and Salt Bridge
For the salt bridge, we use the double line and for the porous disk we use a single line.
- Sun Mar 11, 2018 11:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: FINAL
- Replies: 9
- Views: 1403
Re: FINAL
Everything but 15.9.
- Sun Mar 11, 2018 11:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 6
- Views: 783
Re: Cell Diagrams
In general, have the anode go first and the cathode go next. The inert metals should go on the ends. For those in the middle, don't worry too much about the order as Dr. Lavelle has said that it is not that important.
- Sun Mar 11, 2018 11:12 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Molar Entropy
- Replies: 9
- Views: 1259
Re: Molar Entropy
Generally, the heavier the substance, the higher the molar entropy. This occurs because the energy levels are closer together, which means there are more possible orientations the substance can acquire. Therefore, it will have a higher molar entropy.
- Sun Mar 11, 2018 11:10 pm
- Forum: Balancing Redox Reactions
- Topic: redox
- Replies: 6
- Views: 904
Re: redox
I basically look at what reactant is being oxidized and name that the reducing agent. Then I look atwhat reactant is being reduced and name that the oxidizing agent.
- Sun Mar 11, 2018 11:09 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Processes
- Replies: 2
- Views: 583
Re: Isothermal Processes
furthermore, it is important to note that for isothermal, reversible processes, the change in internal energy is 0 when they are ideal gases. Because they are ideal gases, there is no exhange in energy during the collisions.
- Sun Mar 11, 2018 11:08 pm
- Forum: *Enzyme Kinetics
- Topic: Enzyme
- Replies: 6
- Views: 2444
Re: Enzyme
Enzymes, by defintion, are catalysts. Therefore, they work by speeding up the reaction and not by slowing down.
- Sun Mar 11, 2018 11:07 pm
- Forum: Calculating Work of Expansion
- Topic: Midterm 4a
- Replies: 5
- Views: 907
Re: Midterm 4a
Because we know its constant external pressure, we automatically know that its undergoing an irreversible expansion.
- Sun Mar 11, 2018 11:06 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates
- Replies: 6
- Views: 749
Re: Intermediates
Yes. An intermediate is just a substance that is produced and used in the reaction in a manner that it isnt shown in the final reaction. Because this occurs, it will be an intermediate even if it is isnt shown in step 3
- Sun Mar 11, 2018 11:05 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates
- Replies: 2
- Views: 453
Re: Intermediates
We can determine the intermediates of the reaction by looking at which cancel out throughout the reaction. By doing this, we can also figure out the number.
- Sat Mar 10, 2018 1:39 pm
- Forum: Student Social/Study Group
- Topic: Chem 14BL Exchange
- Replies: 1
- Views: 521
Chem 14BL Exchange
Hi! Im posting here about this because Im desperate LOL. I am currently enrolled next quarter in chem 14BL with casey in lab 1j (Thursday 6:30 pm - 9:20 pm). I am looking to exchange with anyone from casey or the other professor for a different time lab with chem 14BL. Please comment below if intere...
- Mon Mar 05, 2018 12:07 am
- Forum: General Rate Laws
- Topic: general rate laws
- Replies: 3
- Views: 541
Re: general rate laws
Yes this is the general rule
- Mon Mar 05, 2018 12:06 am
- Forum: General Rate Laws
- Topic: zero order in rate laws
- Replies: 8
- Views: 1039
Re: zero order in rate laws
We can include them but its . not needed.
- Mon Mar 05, 2018 12:06 am
- Forum: Zero Order Reactions
- Topic: Identifying zero order
- Replies: 6
- Views: 936
Re: Identifying zero order
You need the table to identify 0 order reactions
- Sun Feb 25, 2018 11:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Metals in Cell Diagrams
- Replies: 3
- Views: 498
Re: Metals in Cell Diagrams
I believe so.
- Sun Feb 25, 2018 11:30 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential
- Replies: 4
- Views: 585
Re: Cell Potential
It just the standard because we can only calculate the change rather than the actual value
- Sun Feb 25, 2018 11:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: how to write a cell diagram [ENDORSED]
- Replies: 7
- Views: 2012
Re: how to write a cell diagram [ENDORSED]
Have the anode then cathode. The inert metals should be on the outside. besides that dont stress
- Fri Feb 23, 2018 10:57 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: 14.55 homework
- Replies: 1
- Views: 535
Re: 14.55 homework
In aqueous solutions, water can be oxidized or reduced as well.
- Mon Feb 19, 2018 3:44 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing H
- Replies: 2
- Views: 413
Re: Balancing H
For basic solutions, to balance O's we use water. Then to balance H's, we use OH's and H2Os on both side.
- Mon Feb 19, 2018 3:41 pm
- Forum: Balancing Redox Reactions
- Topic: Half reaction of O3 to O2
- Replies: 1
- Views: 969
Re: Half reaction of O3 to O2
On the right, you see two hyrdroxide ions. This means that there is -2 on that side. To balance the equation, you need negative 2 on the other side. This is why we have 2 electrons.
- Mon Feb 19, 2018 3:40 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2
- Replies: 3
- Views: 603
Re: Test 2
We will have to know how to do both. The list of constants and equations is on his website.
- Sun Feb 18, 2018 6:26 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Arranging in order of increasing strength
- Replies: 5
- Views: 4206
Re: Arranging in order of increasing strength
but even then, when you look them up there seem to be several possible values. How do you know which one to use.
- Sun Feb 18, 2018 5:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram
- Replies: 2
- Views: 401
Re: Cell diagram
In question 14.21a, we have mercury. Mercury, while a metal, is liquid at room temp. In the answer key, we dont have a inert metal there. Do we use inert metallic components for all metals?
- Sun Feb 18, 2018 5:38 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: reversible system
- Replies: 9
- Views: 1171
Re: reversible system
Delta s total will only be 0.
- Sun Feb 18, 2018 5:38 pm
- Forum: Balancing Redox Reactions
- Topic: agents
- Replies: 3
- Views: 481
Re: agents
I just think the oxidation agent is the substance being reduced on the reactants side and the reducing agent is the substance being oxidized on the reactants side.
- Sun Feb 18, 2018 5:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell reactions
- Replies: 1
- Views: 317
Re: Cell reactions
You have to split it up into half reactions. From there, try to see whether oxidation or reduction is occuring. If oxidation is occuring, we have the anode. If reduction is occuring, we have the cathode.
- Tue Feb 13, 2018 9:47 am
- Forum: Administrative Questions and Class Announcements
- Topic: Practice Midterm Winter 2018
- Replies: 10
- Views: 3120
Re: Practice Midterm Winter 2018
How did we calculate heat and work in number 4 on the midterm?
- Mon Feb 12, 2018 8:38 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy sign
- Replies: 5
- Views: 721
Re: entropy sign
If there is net increase of gaseous moles --> increase in entropy. If there is a net decrease --> decrease in entropy. If appearence of aqueous, net increase. if we see an increase in molecular complexity with the products --> net increase.
- Mon Feb 12, 2018 8:36 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Gas Constant, R
- Replies: 6
- Views: 821
Re: Gas Constant, R
We often use 0.0821 when calulating with PV = nrT. For the others, it is possible I suppose.
- Mon Feb 12, 2018 8:35 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units of Delta H
- Replies: 2
- Views: 896
Re: Units of Delta H
They are relatively interchangeable when there is only one mole. But if two mole of the product is formed, if you have it as kj per mole, you would need to multiply your value by 2.
- Mon Feb 12, 2018 8:34 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: delta S(system) vs delta S(surroundings)
- Replies: 4
- Views: 15276
Re: delta S(system) vs delta S(surroundings)
This can only occur in isothermal, reversible reactions. It would not be considered a violation of the second law of thermodynamics (law that says the entropy is always increasing) because these never actually occur in nature.
- Mon Feb 12, 2018 8:33 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible, isothermal reactions
- Replies: 1
- Views: 347
Reversible, isothermal reactions
Do all reversible reactions occur isothermally?
- Sun Feb 11, 2018 11:55 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: troutons rule
- Replies: 3
- Views: 556
Re: troutons rule
we do not need to know this. dont worry about it.
- Sun Feb 11, 2018 11:54 pm
- Forum: Calculating Work of Expansion
- Topic: different ways to calculate w
- Replies: 4
- Views: 580
Re: different ways to calculate w
We use the former with constant pressure and the latter when its not constant pressure. The first is irreversible expansion and the latter is irreversible, isothermal expansion.
- Sun Feb 11, 2018 11:53 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Third Law's W
- Replies: 3
- Views: 566
Re: Third Law's W
W is degeneracy. it doesnt have units. You calculate it by doing the number of orientations ^ (num of molecules)
- Fri Feb 09, 2018 2:12 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Question 9.21
- Replies: 4
- Views: 549
Re: Question 9.21
If it is in the same direction, you know there is only one possible orienation. Therefore, regardless of how many molecules, the entropy using the boltzman equation will still be found to be 0. This occurs because the W in this equation is found by (# of possible orientations) ^ (# of molecules). In...
- Fri Feb 09, 2018 2:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Slides
- Replies: 6
- Views: 916
Re: Lecture Slides
The lecture slides are in the course reader than he no longer sells. Getting this would be your best bet.
- Fri Feb 09, 2018 2:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delta G=0
- Replies: 6
- Views: 1498
Re: delta G=0
When delta g is 0, it just means that it is at equilibrium. It is not enough to assume the other two quantities to alse be at 0.
- Fri Feb 09, 2018 2:08 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode and cathode
- Replies: 9
- Views: 1374
Re: Anode and cathode
At the anode, oxidation is occuring. At the cathode, reduction is occuring. If you know these concepts and look at the diagram enough, you will be able to distinguish the two
- Fri Feb 09, 2018 2:07 pm
- Forum: Phase Changes & Related Calculations
- Topic: Units for Internal Energy
- Replies: 5
- Views: 707
Re: Units for Internal Energy
I think its preferable to use KJ but you could use either one
- Fri Feb 09, 2018 2:06 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Calculating the change in entropy with constant pressure
- Replies: 2
- Views: 413
Calculating the change in entropy with constant pressure
When the question says the reaction is occuring at constant pressure, can we use C instead of C (p,m) in our equation (change in S = nC(p,m)ln(T2/T1)? Thanks!
- Thu Feb 01, 2018 11:15 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Mass and molar entropy
- Replies: 3
- Views: 1131
Mass and molar entropy
Why do substances with larger masses have larger molar entropies?
- Thu Feb 01, 2018 11:13 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Molar Entropy
- Replies: 2
- Views: 465
Re: Molar Entropy
The molar entropy is basically the entropy per mole of a substance. If you want to find the molar entropy, you need to know how many possible positions the molecules has as in number 25. Then, you have an exponent with Avagadoros number. You plug all this in the boltzman equation and you should be g...
- Thu Feb 01, 2018 11:10 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: The value of Cp
- Replies: 8
- Views: 1515
Re: The value of Cp
On the test, you will be given the table of values that will help you solve for cP
- Thu Jan 25, 2018 8:07 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Combustion Equations [ENDORSED]
- Replies: 4
- Views: 461
Re: Combustion Equations [ENDORSED]
The book says that water in the liquid form will be formed only with organic compounds. When it is not an organic compund, then gas will be formed.
- Thu Jan 25, 2018 8:04 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reaction enthalpy involving H-H
- Replies: 2
- Views: 384
Re: Reaction enthalpy involving H-H
Bond enthalpy is the amount of energy to break one mole of the substance. On the other hand, enthalpy of formation is the amount of energy required to make the substance by substances in their standard states (the state at which they will be found at 1 atm). H2 at one atm is in gas. Therefore, becau...
- Thu Jan 25, 2018 8:01 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.49
- Replies: 2
- Views: 350
Re: 8.49
To look for the net production of gas, you simply subtract the moles of the gas on the product side by the moles of gas from the reactants side. The one mole of OF2 is just refering for the final answer to be in per mole.
- Thu Jan 25, 2018 8:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: change in enthalpy
- Replies: 2
- Views: 370
Re: change in enthalpy
I believe it is deltaU = deltaH - delta(n)RT. This goes off of the concept that delta u is equal to q + w. (AKA the second one). Work is the second one. This occurs because of the idea of what the work is being done on or by what. In expansion, the work is being done ON the surroundings BY the syste...
- Thu Jan 25, 2018 11:34 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat and temp difference
- Replies: 2
- Views: 358
Heat and temp difference
Why is it that in isothermal, reversible expansion heat can be done if heat is defined as the transfer of energy due to a temperature difference? I understand that the change in internal energy must be 0 for ideal gases so heat must be involved but I dont understand it past this. Thanks!
- Tue Jan 23, 2018 5:36 pm
- Forum: Calculating Work of Expansion
- Topic: Natural Log
- Replies: 1
- Views: 238
Re: Natural Log
Well, usually for irreverisible, work = -Pex * (delta V). I am not sure where your equation came from. I believe in this class for reversible, isothermal expansion, all you have to worry about is the one with natural log.
- Tue Jan 23, 2018 5:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess' Law fractions
- Replies: 3
- Views: 1176
Re: Hess' Law fractions
In hess's law, we are calculating the overall enthalpy change. Because enthalpy is a state function, we know it isnt pathway dependent. Therefore, it doesn't matter which way it got there. If you have fractions, as long as you changed enthalpy along with it its fine :)
- Tue Jan 23, 2018 5:33 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Monatomic Gas
- Replies: 5
- Views: 779
Re: Monatomic Gas
R is related to the gas constant or 8.3145 J/ (K x mol). It will just be a constant.
- Tue Jan 23, 2018 5:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: R -> P vs. P -> R
- Replies: 3
- Views: 446
Re: R -> P vs. P -> R
For bond enthalpies, I believe you got the order wrong. It should be reactants - products. This idea is built on the idea that to break bonds in the reactants. To build the bonds in the products, there is a release of energy. Therefore, there is reatants - products.
- Tue Jan 23, 2018 5:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Combustion of liquids
- Replies: 4
- Views: 729
Combustion of liquids
Hello! When a liquid combusts, will liquid water be produced and not gaseous water? Does this always happen? I am asking this specifically in reference to num 93 in which the combustion of c6h6 seems to produces liquid water. Thanks!
- Mon Jan 15, 2018 10:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: Types of Systems
- Replies: 10
- Views: 1449
Re: Types of Systems
In a closed system, there is an exchange of energy but not matter. The example in the book given is a refrigerator coil. This is a closed system because the coil cools the refrigerator through the transfer of energy. There is no exchange of the fluid, however, In contrast, in an isolated system, the...
- Mon Jan 15, 2018 10:11 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.77
- Replies: 2
- Views: 238
Re: 8.77
This concept goes back to 14A. In reasonance, delocalization occurs. Because the electrons are spread over a wider area, the resulting substance is more stable because there are fewer electron electron repulsions.
- Mon Jan 15, 2018 10:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: rxn enthalpy vs. rxn internal energy
- Replies: 1
- Views: 276
Re: rxn enthalpy vs. rxn internal energy
I think because we are supposed to be looking at it in terms of the absolute value. In chemistry, we always take the system's perspective. In physics, however, we usually take the surrounding's perspective. Because of this discepancy, we look at it in terms of absolute value. Please don't hesitate t...
- Mon Jan 15, 2018 10:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess Law
- Replies: 4
- Views: 498
Re: Hess Law
Yes you can! These properties are all possible because enthalpy is a state function. In other words, it doesnt matter how it got there. The end result will still be the same.
- Mon Jan 15, 2018 10:06 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Homework 8.29
- Replies: 5
- Views: 541
Re: Homework 8.29
If you think about it, the more atoms there are, the more heat is required to raise the substance by 1 degree celsius. Therefore, because NO2 has 3 atoms rather than only 2, it takes more heat because there are more atoms that can absorb the heat.
- Mon Jan 15, 2018 10:04 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat and Enthalpy
- Replies: 3
- Views: 437
Heat and Enthalpy
Why is it that heat at constant pressure (enthalpy) is considered a state function but not heat? Thanks!
- Fri Jan 12, 2018 11:23 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Most Stable Forms
- Replies: 4
- Views: 1031
Re: Most Stable Forms
For it to be the most stable form, it must be the one that is most pure. Some of them you just have to memorize. But there are some that you can figure out. All noble gases are most stable in the element phase as a gas. All diatomic gases (such as N2, O2, Cl2, F2, H2, etc.) are the most stable in th...
- Fri Jan 12, 2018 11:15 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Example 8.13
- Replies: 2
- Views: 355
Re: Example 8.13
I have two questions regarding this question. 1. How do you know which atoms you need to break/form during this reaction? 2. Where did they get the average energy required to break/form the bonds? Alright, so for the first one. Draw out the lewis structures of each of the reactants and products. On ...
- Fri Jan 12, 2018 11:10 am
- Forum: Phase Changes & Related Calculations
- Topic: Work done BY vs. Work done ON [ENDORSED]
- Replies: 5
- Views: 588
Re: Work done BY vs. Work done ON [ENDORSED]
This is how I think about it. Imagine work as the direction of the push. If the push is on the system (such as compression as the volume is becoming smaller), it would be work done on the system. Because work is done on the system, we know the work must be done by the surroundings. If the push is on...
- Fri Jan 12, 2018 11:06 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Type of system for mercury in thermometer
- Replies: 5
- Views: 1377
Re: Type of system for mercury in thermometer
It would be a closed system. In a closed system, there is a transfer of energy but not of matter. Because it's in a tube, the mercury can't escape. But it can respond by changes in volume based on the transfer of energy through heat. Therefore, its a closed system.
- Fri Jan 12, 2018 11:05 am
- Forum: Phase Changes & Related Calculations
- Topic: Expansion and change in pressure
- Replies: 4
- Views: 370
Expansion and change in pressure
So I was working on a problem that had to do with expansion and a subsequent lower internal energy. The question asked if the pressure of the gas would be higher or lower when these changes are completed. I was under the assumption that because there is an inverse relationship between pressure and v...
- Fri Jan 12, 2018 11:01 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ideal Gases
- Replies: 1
- Views: 234
Ideal Gases
Why is it that with ideal gases, there is no change in internal energy? Thank you!
- Wed Jan 10, 2018 9:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.73a
- Replies: 1
- Views: 228
8.73a
In this question, we are supposed to use bond enthalpies to estimate the reaction enthalpy for 3C2H2(g)-->C6H6(g). In the solutions manual, it says that only 6 C H bonds are formed (where the bond is between a single and double). It seems to me that 4 C - H bonds are formed as well. Can someone plea...
- Wed Jan 10, 2018 9:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Most Stable Form for an Element
- Replies: 4
- Views: 634
Re: Most Stable Form for an Element
i believe it means the way it sounds. the state it is most likely to be found in nature
- Mon Jan 08, 2018 10:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Question 8.25
- Replies: 4
- Views: 657
Re: Question 8.25
The rest of the question is not important. The question is asking us only to find the change in internal energy. Therefore, we should only be looking for changes in q and w. We find c (the heat capacity) so that we can use this value later to multiply it by the temperture change in the second experi...
- Mon Jan 08, 2018 10:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy and Temperature [ENDORSED]
- Replies: 4
- Views: 503
Re: Enthalpy and Temperature [ENDORSED]
Today in class we learned that enthalpy is related to heat. Given that temperture is defined as the average kinetic energy of particles, this definition does not make it hard to understand why the two may be correlated.
- Mon Jan 08, 2018 10:37 pm
- Forum: Phase Changes & Related Calculations
- Topic: Question on 8.21
- Replies: 3
- Views: 396
Re: Question on 8.21
In this question, you have to understand that the heat released by one will be absorbed by the other. Consequently, you will use -q(copper) = q(water). The initial temp of copper is 100 C and the initial temp of water 22 C. Because you know the masses and can find the specific heat, you should autom...
- Mon Jan 08, 2018 10:32 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb and Coffee Cup Calorimeter [ENDORSED]
- Replies: 3
- Views: 709
Bomb and Coffee Cup Calorimeter [ENDORSED]
How is the volume fixed in the bomb calorimeter and not in the coffee cup calorimeter?
- Sat Dec 09, 2017 11:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Question in adding H20 in equilibrium reaction
- Replies: 2
- Views: 757
Re: Question in adding H20 in equilibrium reaction
yes i am confused by this too. a similar question was on one of the modules 15. The photosynthesis reaction, 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(aq) + 6 O2(g), is endothermic. What effect will the following changes have on the equilibrium composition. a) Water is added. b) The partial pressure of CO2 is d...
- Sat Dec 09, 2017 1:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Practice Test Fall 2017 [ENDORSED]
- Replies: 19
- Views: 3407
Re: Practice Test Fall 2017 [ENDORSED]
on worksheet 9 number 1, the question says that x is the equilbrium concentration of so2. I understand that you have to balance the equation, but I don't understand equilbrium concentration would go from x to 2x when the question said that it should be x. Why is it that is is written as 2x instead?
- Fri Dec 08, 2017 8:27 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Pd electron configuration
- Replies: 2
- Views: 773
Pd electron configuration
I was working on the 2013 final exam and one of the questions said that the electron configuration for Pd is [Kr]4d10. Can someone explain to me how this is the case?
- Wed Dec 06, 2017 10:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: ClF3 Lewis acid/ base?
- Replies: 2
- Views: 2195
ClF3 Lewis acid/ base?
Is ClF3 a lewis acid or base and why?
- Sun Dec 03, 2017 11:45 pm
- Forum: Sigma & Pi Bonds
- Topic: Difference between Bonds [ENDORSED]
- Replies: 7
- Views: 1147
Re: Difference between Bonds [ENDORSED]
yes this is correct.
- Sun Dec 03, 2017 11:44 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3078
Re: Q and K [ENDORSED]
The formulas are the exact same.
- Sun Dec 03, 2017 11:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium
- Replies: 3
- Views: 539
Re: Chemical Equilibrium
The solvent is what dissolves the solute. It is usually a liquid in this class. The universal solvent is water. However, it can also be a gas or supercritical fluid. The solvent can not be aqueous as an aqueous solution means that the solvent was water.
- Sun Dec 03, 2017 11:41 pm
- Forum: Octet Exceptions
- Topic: Expanded Octet Rules
- Replies: 7
- Views: 1083
Re: Expanded Octet Rules
Expanded octets become a possibility at 3p. It becomes a possibility bc 3d is right above it. This sub shell can hold more electrons which is why atoms like P, S, and Cl can hold an expanded octet.
- Tue Nov 28, 2017 11:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc vs. Kp
- Replies: 3
- Views: 663
Re: Kc vs. Kp
If the units are already in pressure and it just says k, then you should keep the units in pressure. If the units are already in molarity and it just says k, then you should keep the units in molarity. If it says kc, then make sure to have the units be in molarity. With Kp, have the units be in pres...
- Tue Nov 28, 2017 11:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K and Kc
- Replies: 7
- Views: 1042
Re: K and Kc
When it says Kc, you should be finding the concentrations in molarity. When it says k, if the units are pressure, keep it in pressure. If the units are in molarity, keep it in molarity.
- Mon Nov 27, 2017 10:44 am
- Forum: Naming
- Topic: Ligand order in coordination sphere
- Replies: 3
- Views: 431
Ligand order in coordination sphere
Hello, I am very confused about the order of the ligands within the coordination sphere. When I asked Dr. Lavelle in class, he said that the order didn't matter. This idea is reaffirmed throughout chemistry community. However, within the textbook, it says that the chemical symbols of the ligands sho...
- Mon Nov 27, 2017 10:21 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles (help please) [ENDORSED]
- Replies: 3
- Views: 647
Bond angles (help please) [ENDORSED]
Hello. I am still confused about certain bond angles. I posted this elsewhere but I want to say it again to highlight the discord. This what I feel it to be. Sea-saw : <90, <120, <180 T-structure : <90, <120, <180 Square pyramidal : <90 Square planar : 90 Can someone please verify these all of these...
- Mon Nov 27, 2017 9:40 am
- Forum: Naming
- Topic: 17.31 c and d confusion
- Replies: 5
- Views: 923
Re: 17.31 c and d confusion
Hi Mike, How water is written does not matter, so long as it is correctly written with two hydrogens and one oxygen. H2O and OH2 are equally correct. For part d., because oxalate has the prefix bis-, this has higher priority than "diaqua" as b precedes d. Hope this helps. But I thought th...
- Sun Nov 26, 2017 11:45 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework Help 11.59
- Replies: 2
- Views: 1008
Re: Homework Help 11.59
First, you would have to change moles to molar concentrations. Then you would put all your initial molar concentrations in your ice chart. Then for change, based on the coefficients of the reactants and products, subtract/add the coefficient x x. You subtract for the reactants and add for the produc...
- Sun Nov 26, 2017 11:42 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Unequal Reactant
- Replies: 3
- Views: 552
Re: Unequal Reactant
When there are more reactants than products, the equilibrium sits to the left. This is because the denominator of the K expression is larger than the numerator, which leads to a K value that is less than one meaning that the equilibrium sits to the left. Actually, K is actually not affected by the ...
- Sun Nov 26, 2017 11:38 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordinatiom compound vs TM complex
- Replies: 1
- Views: 227
Re: Coordinatiom compound vs TM complex
Chem_mod said in a different post that they are interchangeable.
- Sun Nov 26, 2017 11:37 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Relation between K and Q
- Replies: 2
- Views: 762
Re: Relation between K and Q
Remember with K and Q products is over reactants. When Q is less than K, we know that must mean that there are more reactants at this point in the system. If there are more reactants, then the reaction will have the tendency to shift to the products. In terms of Gibbs free energy, the outline says t...
- Sun Nov 26, 2017 11:35 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium
- Replies: 3
- Views: 484
Re: Chemical Equilibrium
Are there any specific exceptions we should be aware of for Chemical Equilibrium (in some other chapters there are specific exceptions to know, like chromium and copper for the orbitals)? I suppose one would be if you yield two positive values from your quadratic, you are two use the value of X tha...
- Sun Nov 26, 2017 11:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs. K
- Replies: 3
- Views: 558
Re: Q vs. K
Alissa Stanley 3G wrote:So it is possible for Q and K to be equal, if Q is at equilibrium?
Yes! If Q and K are equal, we know that the mixture has equilibrium composition and has no tendency to change in either direction.
- Sun Nov 26, 2017 11:30 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: How can you determine if a complex is a polydentate?
- Replies: 5
- Views: 1113
Re: How can you determine if a complex is a polydentate?
You determine if its polydentate if there are multiple atoms that have lone pairs on them that can form a coordinate covalent bond. A rule of thumb is that whenever you have Nitrogens, you are sure that the molecule is polydentate. Because there are two nitrogens as there is in ethylenediamine (en) ...
- Sun Nov 26, 2017 11:24 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs. K
- Replies: 3
- Views: 558
Re: Q vs. K
Q can be the concentrations of the reactants and products at any point in the reaction. K can only be the concentrations of the reactants at equilibrium. You go about solving them the same way. By using both Q and K, we can determine which way the reaction is more likely to proceed.
Re: 17.1
Well 17.1 was unassigned and unrelated to what we will be tested on so I assume you meant 17.29? Lewis structures aren't needed. This pdf is very helpful with naming compounds. Memorize it. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/NamingCoordinationCompounds.pdf The charges ...
- Sun Nov 26, 2017 11:11 am
- Forum: Naming
- Topic: Naming (steps)
- Replies: 6
- Views: 750
Re: Naming (steps)
RenuChepuru1G wrote:at what point should you figure out cations versus anions and is there an easy way to do that?
The cations are what has an overall positive charge and the anions are what has an overall negative charge.
- Sun Nov 26, 2017 11:04 am
- Forum: Student Social/Study Group
- Topic: Chapter 17
- Replies: 1
- Views: 447
- Sun Nov 26, 2017 11:03 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium
- Replies: 3
- Views: 484
Re: Chemical Equilibrium
Yes, but it would still be a good idea to do practice problems to familiarize yourself with the topics. Sometimes through practice, you learn exceptions that teachers won't directly teach you.