Search found 28 matches
- Mon Mar 07, 2016 4:16 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Is activation energy a constant?
- Replies: 3
- Views: 1313
Re: Is activation energy a constant?
External factors like pressure and temperature only affect the reaction rate. They do this by increasing the number/energy of collisions, meaning these collisions reach the activation energy more frequently. From my understanding, the only thing that affects activation energy is a catalyst. Hope thi...
- Mon Mar 07, 2016 3:29 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Reverse Activation Energies
- Replies: 1
- Views: 774
Re: Reverse Activation Energies
So reverse activation energies are just imagining the reverse reaction occurring. It's easier to visualize it when you think about the graphs of exothermic and endothermic reactions. exothermic.png It makes sense that the reverse activation energy for an exothermic reaction would be ∆H + Ea since th...
- Mon Mar 07, 2016 3:17 pm
- Forum: *Chem3D
- Topic: Types of strain
- Replies: 3
- Views: 1127
Re: Types of strain
Maybe a little more in detail, Torsional strain is the repulsion between electrons of molecules (methyl groups, for example) on neighboring carbons. When you rotate a molecule around a bond (hence torsional, like torque, which is the force to rotate or twist an object), this is the repulsion when gr...
- Thu Mar 03, 2016 9:45 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Video Competition
- Replies: 66
- Views: 25311
Re: Video Competition
Chemistry Extra Credit Video
Thermodynamics - Deriving the Work Equation for a Reversible and Isothermal Process
Created by:
Divya Prajapati and Annie Qing
(Lecture 2)
Thermodynamics - Deriving the Work Equation for a Reversible and Isothermal Process
Created by:
Divya Prajapati and Annie Qing
(Lecture 2)
- Tue Mar 01, 2016 8:19 am
- Forum: *Electrophiles
- Topic: Equal sign with a line through it
- Replies: 4
- Views: 1405
Re: Equal sign with a line through it
Generally, it means "not equal to."
So, for instance,
.
So, for instance,
- Tue Feb 23, 2016 1:10 am
- Forum: Balancing Redox Reactions
- Topic: Redox Reactions
- Replies: 1
- Views: 395
Re: Redox Reactions
Yes it is different. The reducing agent is oxidized and the oxidizing agent is reduced. If you think about it, oxidation and reduction come in pairs. The oxidizing agent (molecule that causes other molecules to lose electrons) cannot also lose electrons; it must be reduced. The opposite goes for the...
- Tue Feb 23, 2016 1:08 am
- Forum: *Alkanes
- Topic: Saturated vs unsaturated fats
- Replies: 3
- Views: 1653
Re: Saturated vs unsaturated fats
Unsaturated fats are liquids at room temperature because there is at least one double bond. Any non-single bond creates a kink in the structure, not allowing the molecules to crystalize easily.
In contrast, saturated fats are straight chains and pack together much more tightly.
In contrast, saturated fats are straight chains and pack together much more tightly.
- Sun Feb 14, 2016 9:33 pm
- Forum: General Rate Laws
- Topic: Rate laws
- Replies: 1
- Views: 321
Re: Rate laws
From what I understand, I think for our purposes, yes. While differential rate laws in theory simply is the rate as a function of concentration (and we could experimentally measure how the concentration measures in relation to time), the method of initial rates is the easiest. Because t is very clos...
- Sun Feb 07, 2016 10:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 3
- Views: 507
Re: Cell Diagrams
Other than that convention, 1. Put the inert electrodes on the far left and/or far right. (e.g. Pt(s)) 2. Generally, the molecules are put in order of reactants to products on either side of the salt bridge, but I don't think this is a strict rule. *If there's more than one reactant/product, it does...
- Sun Jan 31, 2016 9:35 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Vacuum Scenario
- Replies: 1
- Views: 307
Re: Vacuum Scenario
Yes. Since the external pressure is zero, this is free expansion (nothing to expand against) and the work done is also equal to zero.
- Sun Jan 24, 2016 10:44 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: reversible/irreversible processes
- Replies: 1
- Views: 316
Re: reversible/irreversible processes
Irreversible processes are ones that happen suddenly (e.g. gas being released into a vacuum) whereas reversible processes are done over a theoretically infinite amount of time because the change happens in infinitesimally small parts. In a reversible process, the system is in equilibrium throughout ...
- Sun Jan 17, 2016 10:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: phase changes
- Replies: 1
- Views: 276
Re: phase changes
I'm not sure if this is exactly what you mean but To change from ice to water (and then heat up the water), you have to calculate the heat required for both parts: changing the phase and then heating up the water. So it's easy to do these in order. First we figure out how much energy we need to put ...
- Sun Jan 10, 2016 11:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpy
- Replies: 1
- Views: 316
Re: Standard Enthalpy
Yes. The standard enthalpy of formation for an element in its most stable form is 0 because we define the standard enthalpy of formation as the change in enthalpy between the product and the elements that make it up in its most standard form. Thus in the formation of O2, for example, O2 is both the ...
- Thu Dec 03, 2015 2:17 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Nominal Concentration
- Replies: 1
- Views: 6353
Re: Nominal Concentration
So the dissociation reaction is Ba(OH)_{2}\rightarrow Ba^{2+}+2OH^{-} First, calculate the initial molarity of Ba(OH)_{2} : [Ba(OH)_{2}]=\left ( \frac{0.43 g Ba(OH)_{2}}{0.100 L} \right )\left ( \frac{mol Ba(OH)_{2}}{171.342 g Ba(OH)_{2}} \...
- Tue Nov 24, 2015 12:40 am
- Forum: Ideal Gases
- Topic: Boiling Point of a Liquid
- Replies: 1
- Views: 391
Re: Boiling Point of a Liquid
Yes, the boiling point of a liquid is higher at a lower altitude/higher atmospheric pressure. The boiling point is defined as "the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor." As you decrease altitude...
- Sun Nov 22, 2015 5:17 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Strong Vs. Weak Acids
- Replies: 1
- Views: 353
Re: Strong Vs. Weak Acids
While it's true that the molecules are becoming less polar as you move from F to I, for example, this also means that the bonds between H and the ion are becoming weaker. Because I is a much larger atom than F, the distance between H and I is also much larger than that between H and F. With a weaker...
- Mon Nov 16, 2015 12:31 am
- Forum: Naming
- Topic: Naming [Co (CN)5 (OH2)]^2-
- Replies: 1
- Views: 493
Re: Naming [Co (CN)5 (OH2)]^2-
So first you list the ligands in alphabetical order by their prefix. We have pentacyano (CN)_{5} and monoaqua ( OH_{2} ), so the first part of the naming will be monoaquapentacyano in alphabetical order. Then you list the central metal atom, which is cobalt. To determine the charge on cobalt...
- Mon Nov 16, 2015 12:25 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: HW 17.35
- Replies: 1
- Views: 373
Re: HW 17.35
So, from what I understand, in order for a ligand to be chelating, the "bite angle" or the angle between the two parts of the ligand that will attach to the central metal has to be somewhere around, or less than, 90 degrees. So in 17.35, the NH_{2} parts of the ligand are only less than an...
- Thu Nov 05, 2015 8:20 pm
- Forum: Lewis Structures
- Topic: Organic Lewis structures
- Replies: 1
- Views: 349
Re: Organic Lewis structures
At any end of the line or bend of the structure, we assume there is a carbon atom. We also assume that each carbon atom has four bonds, so hydrogen atoms are assumed to be attached to carbon atoms that don't already have four bonds on it. For example, Organic Chemistry 1.png There are 8 carbon atoms...
- Sun Nov 01, 2015 8:19 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration for Cr^2+
- Replies: 2
- Views: 7801
Re: Electron Configuration for Cr^2+
I think the difference with Cr^2+ is that it's an ion so we're technically removing electrons. When removing electrons, we remove from the valence shell first, in this case from n=4. Thus, we remove the first electron from 4s and the second from 3d to create the ion.
Let me know if this makes sense?
Let me know if this makes sense?
- Sun Nov 01, 2015 8:07 pm
- Forum: Photoelectric Effect
- Topic: Question 6, Quiz 1, Section 3F
- Replies: 1
- Views: 451
Re: Question 6, Quiz 1, Section 3F
I would like to preface this with a "sorry the equation editor isn't working for me." Anyways, From E=h(frequency) and c=(wavelength)(frequency), we can get E=h(c/wavelength). Given the wavelength of the emitted light is 161x10^-9 m, c=3.00x10^8 m/s, and h=6.62608x10^-34 J•s, E=h(c/wavelen...
- Wed Oct 21, 2015 2:49 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Strength In Same Group
- Replies: 6
- Views: 1226
Re: Bond Strength In Same Group
I might be wrong but I think to answer your question, the stronger bond is the one with the more electronegative atom involved. For instance, the CCl_{4} bonds are stronger than those of the CBr_{4} molecule because Cl is a more electronegative atom. Electronegative atoms hold electrons more tightly...
- Mon Oct 12, 2015 5:34 pm
- Forum: Properties of Electrons
- Topic: Atomic Spectra
- Replies: 1
- Views: 339
Re: Atomic Spectra
First, solve for the wavelength's frequency by the equation c=\lambda \nu where c is the speed of light. The energy of that frequency can be solved for by the equation E=h\nu where h is Planck's constant. You can then find the principle quantum number (n) that correlates by the equation E_{n}=-\frac...
- Mon Oct 12, 2015 5:24 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Hydrogen Spectral Series
- Replies: 1
- Views: 368
Re: Hydrogen Spectral Series
The hydrogen spectral series shows the specific amounts of energy needed to transition between two energy levels within hydrogen and can be observed when electrons fall from higher energy levels and emit photons. We observe specific lines or amounts of energy because electrons do not gradually move ...
- Sat Oct 10, 2015 4:45 pm
- Forum: Student Social/Study Group
- Topic: Top of the Hill Study Group
- Replies: 5
- Views: 1084
Re: Top of the Hill Study Group
I'd be interested! I'm in Hedrick Summit.
- Sat Oct 10, 2015 4:35 pm
- Forum: Properties of Electrons
- Topic: Shielding
- Replies: 2
- Views: 885
Re: Shielding
From what I understand, shielding is not a phenomenon that occurs as orbitals change but as the number of shells (quantum number n) changes. So, as you go down the periodic table, the effective charge on an electron decreases because the shells are increasingly farther away from the nucleus and clos...
- Fri Oct 02, 2015 11:32 pm
- Forum: Balancing Chemical Reactions
- Topic: States of Matter In Chemical Equations
- Replies: 2
- Views: 599
Re: States of Matter In Chemical Equations
I believe since the boiling point for CO_{2} is -78.5°C and reactions generally occur above that temperature, CO_{2} is usually found as a gas. If by some chance the reaction occurred under -78.5˚C, I think CO_{2} would be found as a solid (because CO_{2} sublimates) under normal pressure circumstan...
- Fri Oct 02, 2015 11:21 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic radius regarding the bonding of Na and Cl
- Replies: 2
- Views: 422
Re: Atomic radius regarding the bonding of Na and Cl
Yes, I think you're right with the electrostatic repulsion between electrons. Because the number of protons (and therefore positive charge) stays constant as chlorine gains an electron, the electrons aren't pulled closer in any way and instead spread out within the "shell" as an effect of ...