Search found 61 matches
- Thu Mar 14, 2019 11:25 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: H+ in Cell Diagram
- Replies: 1
- Views: 335
H+ in Cell Diagram
Can someone give in an example of an equation in which you would include the Hydrogen ion in the cell diagram? How would you include it, because you most likely will not use a porous disk to separate the ions since H+ will be in the same phase as one of the ions. But how do you know when to include ...
- Thu Mar 14, 2019 11:03 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Molecularity
- Replies: 5
- Views: 443
Re: Molecularity
No, molecularity only depends on the molecules which react so we are only looking at the reactants. When considering molecularity we are evaluating how many molecules are colliding which again would only be considering the reactants.
- Thu Mar 14, 2019 11:00 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 6
- Views: 559
Re: Catalysts
It is important to differentiate between a catalyst and an intermediate. A catalyst is present from the beginning of the reaction and is not consumed. However, an intermediate is produced by the reaction and is used up in the reaction.
- Thu Mar 14, 2019 10:58 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation
- Replies: 4
- Views: 440
Re: Arrhenius Equation
I dont recall prof Lavelle explaining in class but I remember him saying in this class we will generally be using A=1.
- Fri Mar 08, 2019 8:00 pm
- Forum: Zero Order Reactions
- Topic: how do we tell if a reaction is zero order?
- Replies: 5
- Views: 556
Re: how do we tell if a reaction is zero order?
If the graph of [A] vs time is linear, then the reaction is zero order because the reaction rate is independent from the concentration of reactants.
- Fri Mar 08, 2019 7:58 pm
- Forum: Zero Order Reactions
- Topic: Determining Rate Orders
- Replies: 3
- Views: 388
Re: Determining Rate Orders
You look at when the concentration of one reactant changes and the amount their corresponding reaction rates change. You then raise the concentration to the power "n" and set it equal to the change in reaction rates to find the exponents of the reactants in the rate law. Once you find the ...
- Fri Mar 08, 2019 7:46 pm
- Forum: General Rate Laws
- Topic: Graph of ln[A] against time
- Replies: 4
- Views: 1657
Re: Graph of ln[A] against time
If the graph of [A] vs time is linear then it's a Zero Order reaction.
If the graph of ln[A] vs time is linear then it's a First Order reaction.
If the graph of 1/[A] vs time is linear then it's a Second Order reaction.
If the graph of ln[A] vs time is linear then it's a First Order reaction.
If the graph of 1/[A] vs time is linear then it's a Second Order reaction.
- Sun Feb 24, 2019 7:13 pm
- Forum: Balancing Redox Reactions
- Topic: 1/2 Rxns: Elements vs. Compounds
- Replies: 3
- Views: 314
1/2 Rxns: Elements vs. Compounds
When balancing half reactions, should we be just writing down the element that is involved or should we be including the entire compound that that element is apart of? Does it depend on the reaction and if the compound includes oxygen/hydrogen?
- Sun Feb 24, 2019 7:10 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Half Reactions
- Replies: 3
- Views: 303
Re: Balancing Half Reactions
As said above, this is because the standard cell potential is an intensive property so it is not affected by a change in coefficients. However, if it was an extensive property, like Enthalpy, you would multiply its value by a change in the coefficients.
- Sat Feb 23, 2019 1:37 pm
- Forum: Balancing Redox Reactions
- Topic: Reactant as Reducing and Oxidizing Agent
- Replies: 1
- Views: 213
Reactant as Reducing and Oxidizing Agent
I’m confused on how to balance a redox reaction when there is one reactant that acts as both the reducing and oxidizing agent. For example, in #6K3 in the 7th edition textbook, it gives the equation: Cl2(g) —> HClO(aq) + Cl2(g) Cl2 is the only reactant and acts as both the reducing and oxidizing age...
- Thu Feb 21, 2019 9:35 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode v. Cathode
- Replies: 9
- Views: 918
Re: Anode v. Cathode
One way to remember which (anode or cathode) is redox or oxidation is by using:
A RED CAT (redox--cathode)
AN OX (anode--oxidation)
A RED CAT (redox--cathode)
AN OX (anode--oxidation)
- Thu Feb 21, 2019 9:33 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge/Porous Disk
- Replies: 5
- Views: 558
Re: Salt Bridge/Porous Disk
It is most important to know they allow ion transfer which helps maintain neutral solutions.
- Tue Feb 19, 2019 9:24 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Negative Delta G
- Replies: 7
- Views: 3925
Re: Negative Delta G
Also it is important to remember when Delta G is negative the reaction is spontaneous!
When it is positive it is non spontaneous.
When it is positive it is non spontaneous.
- Sun Feb 10, 2019 3:31 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Predict entropy change
- Replies: 3
- Views: 536
Re: Predict entropy change
Gases have greater entropy, because gas molecules expand to fill their whole container and can move around freely so there is more disorder... So since this reaction goes from having one mole of gas to having zero, its entropy decreases.
- Sun Feb 10, 2019 3:27 pm
- Forum: Calculating Work of Expansion
- Topic: Work equations
- Replies: 2
- Views: 329
Re: Work equations
hi miriam! They both represent different things.. the lowercase w is to calculate work done on the system which is used for reversible and irreversible reactions. While, the capital W represents degeneracy, so it used to calculate residual entropy.
- Sun Feb 10, 2019 3:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Quick Conceptual question
- Replies: 7
- Views: 859
Re: Quick Conceptual question
In addition to what was said above, entropy can determine if a reaction is spontaneous (favorable) or not but Enthalpy cannot determine this.
Total entropy >>0 - Spontaneous
Total entropy <<0 - Non spontaneous
Total entropy >>0 - Spontaneous
Total entropy <<0 - Non spontaneous
- Mon Feb 04, 2019 5:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 2
- Views: 293
Re: Hess's Law
I saw a problem like this too, and was wondering if we can just use the enthalpies of formations for each of the compounds and use the equation:
Enthalpy of formation (products) - Enthalpy of formation (reactants)
Instead of doing Hess’s Law? Or will you get different answers?
Enthalpy of formation (products) - Enthalpy of formation (reactants)
Instead of doing Hess’s Law? Or will you get different answers?
- Mon Feb 04, 2019 5:21 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Important Thermochemistry Equations
- Replies: 3
- Views: 405
Important Thermochemistry Equations
Does someone mind listing all the important equations we need to know for the thermochemistry unit? I get confused when reading the book, which equations are necessary to know and which are just examples...
Thank you!!
Thank you!!
- Sun Feb 03, 2019 1:02 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law vs. Rxn Enthalpies
- Replies: 2
- Views: 467
Hess's Law vs. Rxn Enthalpies
How do you know when to you use Hess's Law to calculate the overall reaction Enthalpy versus when to use the equation: Enthalpy of formation for products - the enthalpy of formation for the reactants For example #4D15 in the 7th edition, I used the equation above but the solutions manual used Hess's...
- Thu Jan 31, 2019 4:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Work Calculation
- Replies: 3
- Views: 297
Work Calculation
I remember Lavelle going over this but couldn't remember his explanation... why must the constant pressure have a negative sign in front for the calculation of work done on a system?
- Thu Jan 31, 2019 4:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reversible Processes
- Replies: 2
- Views: 281
Reversible Processes
Why is the greatest work done for processes that take place reversibly when the definition of a reversible process is one that can be reversed by a very small change?
- Thu Jan 31, 2019 4:02 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Different Kinds of Symptoms
- Replies: 6
- Views: 1222
Different Kinds of Symptoms
Can someone please give examples for open, closed, and isolated systems? I'm still kind of confused by the definitions of them all so I think examples would help me understand the concepts better. Thanks!
- Wed Jan 23, 2019 11:46 am
- Forum: Ideal Gases
- Topic: Pressure in terms of mols
- Replies: 3
- Views: 430
Re: Pressure in terms of mols
Consider pressure in terms of volume as well. When the number of moles stays the same and the volume decreases, the pressure will increase because now there is a more concentrated system. Same vice versa, when the volume increases, the solution is less concentrated so the pressure decreases.
- Wed Jan 23, 2019 11:44 am
- Forum: Ideal Gases
- Topic: The Difference between Q and Kc [ENDORSED]
- Replies: 18
- Views: 8552
Re: The Difference between Q and Kc [ENDORSED]
We use Q to determine which way the reaction must proceed to reach equilibrium which can also help us in settling up our ICE boxes.
- Wed Jan 23, 2019 11:42 am
- Forum: Ideal Gases
- Topic: Units for concentration
- Replies: 5
- Views: 507
Re: Units for concentration
Yes it is equivalent... it is just suggested to use mol/L when doing calculations so you are more aware of what units are being used and canceled and which remain.
- Tue Jan 15, 2019 6:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Same/different @ equilibrium
- Replies: 2
- Views: 138
Same/different @ equilibrium
Is the only thing that remains the same at equilibrium between two different size samples of the same reactants and products, the equilibrium expression (kc)? How come the ratio without the exponents changes but the ratio with the exponents doesn't change?
- Tue Jan 15, 2019 6:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier - Volume
- Replies: 2
- Views: 180
Le Chatelier - Volume
I'm confused on how to explain your observation for the change in volume in relation to the Le Chatelier principle. Lavelle said not to discuss the increase or decrease in moles when the volume is changed, but rather to discuss the reaction quotient. How would you do this? Can someone provide an exa...
- Tue Jan 15, 2019 6:35 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction Quotient
- Replies: 10
- Views: 741
Re: Reaction Quotient
The reaction quotient can be calculated the same way as K. The concentration values used for the calculation of Q are the values before the reaction reaches equilibrium, and the values used to calculate K are the values when the reaction is at equilibrium.
- Wed Jan 09, 2019 9:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Table
- Replies: 4
- Views: 154
Re: ICE Table
We assume the concentrations are very low and close to zero, so to make the calculations easier we just use 0.
- Wed Jan 09, 2019 9:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Spectator Ions and Equilibrium Constants
- Replies: 2
- Views: 1301
Re: Spectator Ions and Equilibrium Constants
A spectator ion is unchanged on both sides of the reaction and does not affect equilibrium so it is therefore not included in the equilibrium expression.
- Wed Jan 09, 2019 8:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: finding K Value
- Replies: 3
- Views: 174
Re: finding K Value
In the expression, you must put the concentrations of the reactants and products to the power of their stoichiometric coefficients!
- Mon Dec 03, 2018 7:04 pm
- Forum: Conjugate Acids & Bases
- Topic: basicity strength
- Replies: 3
- Views: 602
Re: basicity strength
It may also be helpful to memorize the main strong bases... group 1 and 2 hydroxides! It will be easier/faster to identify the strong base if you know the general strong bases.
- Mon Dec 03, 2018 7:01 pm
- Forum: Bronsted Acids & Bases
- Topic: Water with Acids and Bases
- Replies: 3
- Views: 371
Re: Water with Acids and Bases
You will know if water acts as an base or an acid based off of what compound it is reacting with. If it is reacting with a base, it will act as an acid and donate protons; however, if it is reacting with an acid, it will act as a base and accept protons. And I believe the strength of an acid/base do...
- Mon Dec 03, 2018 6:56 pm
- Forum: Amphoteric Compounds
- Topic: Definition
- Replies: 5
- Views: 450
Re: Definition
Amphoteric refers to a compound that can act as either a base or an acid. The most well known example of an amphoteric compound is water, because it can act as both a base and acid.
- Wed Nov 28, 2018 11:13 am
- Forum: Dipole Moments
- Topic: Polarizability vs Polarizing power
- Replies: 8
- Views: 670
Re: Polarizability vs Polarizing power
Polarizability is related to anions and how readily able they are to have their electron cloud distorted by the cation. Polarizability increases as atomic radius increases because more electron shielding. Polarizing power is related to cations and their ability to distort the electron cloud of anion...
- Wed Nov 28, 2018 11:10 am
- Forum: Dipole Moments
- Topic: Size and IM interactions
- Replies: 2
- Views: 136
Re: Size and IM interactions
This is referring to polarizability. The London Dispersion Forces are stronger when the anion is more polarizable and the anion has higher polarizing power. And the anion is more polarizable when it is larger because there is more electron shielding.
- Wed Nov 28, 2018 11:08 am
- Forum: Dipole Moments
- Topic: Interaction Potential Energy
- Replies: 4
- Views: 723
Re: Interaction Potential Energy
No I don't think we have to know the formula since we never really did any math with it, I think you just have to know the general concept of how potential energy relates to the behavior of IM forces.
- Mon Nov 19, 2018 9:11 pm
- Forum: Hybridization
- Topic: D-orbital
- Replies: 5
- Views: 456
Re: D-orbital
Yes, Lavelle says he prefers to put the d-orbital after the s-orbital but either is correct notation!
- Mon Nov 19, 2018 9:02 pm
- Forum: Hybridization
- Topic: electron density in regards to # of hybrid orbitals
- Replies: 4
- Views: 429
Re: electron density in regards to # of hybrid orbitals
In class today, Professor Lavelle said the number of hybrid orbitals = the number of electron density regions around the central atom.
- Mon Nov 19, 2018 8:59 pm
- Forum: Hybridization
- Topic: Unhybridized orbitals
- Replies: 10
- Views: 1359
Re: Unhybridized orbitals
I am also still confused on if all lewis structures obtain hybridized orbitals? Or how do you determine if they do or don't?
- Thu Nov 15, 2018 12:19 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: AX and AXE
- Replies: 2
- Views: 486
AX and AXE
I'm not sure if we have to know this, but I remember in high school chem, we had to derive AX2 or AX2E2 or whatever based off of the number of bonding pairs and lone pairs on the central atom and from that, you could derive the shape of the molecule. I remember knowing this helped me a lot but I can...
- Thu Nov 15, 2018 12:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: What to memorize in VSEPR?
- Replies: 8
- Views: 982
Re: What to memorize in VSEPR?
I'm assuming we have to memorize the angles too because we are supposed to understand the concept of how lone pairs affect the bond angles, so therefore you should be able to derive the angles based on the shape of the molecule.
- Thu Nov 15, 2018 12:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Will we have to calculate bond angles?
- Replies: 8
- Views: 680
Re: Will we have to calculate bond angles?
I think we have to know the bond angles of each shape and basically how those angles are derived. For instance, you have to know that by adding lone pairs, the angles will be affected and will generally become smaller.
- Fri Nov 09, 2018 7:41 am
- Forum: Octet Exceptions
- Topic: The center atom
- Replies: 20
- Views: 3160
Re: The center atom
Oxygen is the center atom because you also have to consider the bond formation. Oxygen forms more bonds than Chlorine, so it should be the center atom, since there are two other atoms to form bonds with.
- Fri Nov 09, 2018 7:37 am
- Forum: Electronegativity
- Topic: Electron Affinity vs. Ionization Energy
- Replies: 8
- Views: 791
Re: Electron Affinity vs. Ionization Energy
Electron affinity is the energy given off when electrons are added to the atom. So basically, the electron affinity of an atom can determine if the atom wants electrons or not. On the other hand, ionization energy is the energy needed to remove an electron from an atom. They both increase across the...
- Fri Nov 09, 2018 7:35 am
- Forum: Electronegativity
- Topic: What are the trends useful for?
- Replies: 12
- Views: 909
Re: What are the trends useful for?
All of these trends feed off of each other so it is important to understand all of them. For instance, ionization energy feeds off of atomic radius, as the smaller the radius, the higher the ionization energy, because the pull from the nucleus is greater. Another significant reason to know these tre...
- Wed Oct 31, 2018 2:48 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Stable Condition
- Replies: 8
- Views: 2519
Re: Stable Condition
I believe molecules are always the most stable when the formal charge is equal to zero because that shows that the molecule is neutral.
- Wed Oct 31, 2018 2:46 pm
- Forum: Resonance Structures
- Topic: How does a resonance structure work?
- Replies: 10
- Views: 1075
Re: How does a resonance structure work?
Resonance basically means that the lewis structure of a molecule can be written in different forms, but the one that is the most appropriate to use would be the one that has a formal charge of 0, because it means it is most stable. The general lewis structure of molecules with resonance would be the...
- Wed Oct 31, 2018 2:44 pm
- Forum: Ionic & Covalent Bonds
- Topic: Interactions between ions
- Replies: 3
- Views: 359
Re: Interactions between ions
If it is not included in one of the sections listed in his outline or if he didn't go over it in lecture (which I think he only briefly addressed it), I don't think we will have to know it for the midterm! I don't think this topic will be focused on in the midterm, I would focus on the other ones li...
- Thu Oct 25, 2018 9:07 am
- Forum: Quantum Numbers and The H-Atom
- Topic: spin
- Replies: 4
- Views: 425
Re: spin
Since this number is determined off of the electron configuration, how do you know when to draw an arrow faced down or faced up so you can determine if it is +1/2 or -1/2?
- Thu Oct 25, 2018 9:03 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Electron Configurations
- Replies: 3
- Views: 256
Re: Electron Configurations
4s would logically come next because it is the shell that is after Argon, however, in this case as we move onto the 3d level, we have to remember that the 3d level is less in energy than the 4s level. Electron configurations are always written in lowest energy to highest energy, so this electron con...
- Thu Oct 25, 2018 9:00 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spins
- Replies: 4
- Views: 352
Re: Spins
In addition to the all the previous replies, spin up and spin down is referenced when an atom has unpaired electrons (it subshells aren't filled).
- Thu Oct 18, 2018 1:36 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: ground state electron configuration
- Replies: 5
- Views: 2274
Re: ground state electron configuration
I am also confused on this... For when you are asked to write the electron configuration, when do you not fill up the first orbital and move onto the next one? Like if you were to write 1s2,2s2,2p6,3s1,3p3,3d... How do you determine which orbitals you don't fill?
- Thu Oct 18, 2018 1:30 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: l and ml
- Replies: 1
- Views: 78
l and ml
I am still confused on the variables l and ml that mean the orbital angular momentum quantum number and the magnetic quantum number. How do you determine both of these values when they give you a specific orbital?
- Mon Oct 15, 2018 2:58 pm
- Forum: Student Social/Study Group
- Topic: Note Taking
- Replies: 145
- Views: 15060
Re: Note Taking
I agree that sharing this info will be very beneficial for all of us! Personally, what I find to be quite helpful is handwriting my notes in class, so I can include equations and diagrams, but when I get back from class I type up my notes that I had just wrote down in class. I do this so that I am r...
- Wed Oct 10, 2018 11:25 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: What does ground state mean? [ENDORSED]
- Replies: 4
- Views: 896
Re: What does ground state mean? [ENDORSED]
Ground state means that the atom is not ready to bond with another atom, as it would be if it were in the excited state. Therefore, for the electron configuration for atom in the ground state, if possible, all of the electrons would be paired. On the other hand, for the excited state, there would be...
- Wed Oct 10, 2018 11:20 pm
- Forum: Properties of Light
- Topic: Do I need to memorize the Light Spectrum? [ENDORSED]
- Replies: 13
- Views: 899
Re: Do I need to memorize the Light Spectrum? [ENDORSED]
I was curious about this too, because I noticed in lecture today, Lavelle was asking the class what region a certain wavelength range was, so I am wondering if we have to know the general wavelength of each region or if we just have to know the relative strength.
- Wed Oct 10, 2018 11:16 pm
- Forum: Properties of Light
- Topic: Problem 1.23
- Replies: 2
- Views: 176
Re: Problem 1.23
As Melody said, I believe the book used the more exact number to match the number of sig figs in the data provided, and also it is helpful to use the more exact number instead of rounding to get a more precise calculation. However, since Lavelle noted 6.626 and most resources note Planck's constant ...
- Wed Oct 03, 2018 9:20 pm
- Forum: SI Units, Unit Conversions
- Topic: Formula Units??
- Replies: 3
- Views: 532
Formula Units??
I am still confused what formula units are... In fundamentals E. 25 it says determine the number of KNO3 formula units in 0.750 mol KNO3.. Is that the same as saying the number of molecules/atoms? Where I am guessing you would use the conversion of moles to avogadros number.
- Wed Oct 03, 2018 7:32 pm
- Forum: SI Units, Unit Conversions
- Topic: Week 2 homework
- Replies: 2
- Views: 248
Week 2 homework
For week 2 homework that is due during our discussion session, should we be doing 7 problems that are still from the high school review section or should we be moving onto the next topics? I was wondering because some discussions are after only one of the lectures so we haven't reviewed much of the ...
- Mon Oct 01, 2018 12:16 pm
- Forum: SI Units, Unit Conversions
- Topic: Office Hours [ENDORSED]
- Replies: 2
- Views: 187
Office Hours [ENDORSED]
Do office hours begin this week? Also, when do the peer learning sessions start and what do those entail?