## Search found 65 matches

Sat Jan 16, 2021 6:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in pressure due to inert gas
Replies: 6
Views: 24

### Re: Change in pressure due to inert gas

To add on to everyone else's posts, when you add an inert gas, they do not participate in the reaction because they have a full outer shell. Therefore, they are unreactive and will not cause changes to the partial pressures of the other gases.
Sat Jan 16, 2021 6:29 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Autoprotolysis
Replies: 2
Views: 20

### Autoprotolysis

Which types of compounds exhibit autoprotolysis? I understand what it is, but are there certain types of substances besides water that exchange protons regularly? Do all weak acids or bases do this?
Sat Jan 16, 2021 6:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H concepts
Replies: 3
Views: 19

### Re: 5H concepts

Yes, this is correct! Also, you can use reverse reactions with the equilibrium constant 1/K, and you can multiply equations by a number to get new coefficients. The equilibrium constant would be raised by that number, K^x.
Sat Jan 16, 2021 5:20 pm
Forum: Ideal Gases
Topic: Kc vs. Kp
Replies: 14
Views: 40

### Re: Kc vs. Kp

Also, if you are given gas concentrations instead of partial pressures, it is ok to find Kc unless the problem states otherwise.
Sat Jan 16, 2021 5:18 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Textbook D.5
Replies: 1
Views: 20

### Re: Textbook D.5

I can't tell what you did wrong from this information, but I can give some suggestions. Make sure you are using the correct value for Kb. Then, make sure to pay attention to the problem. X will be the concentration of OH-, not H3O+. You might be confusing pOH with pH.
Sun Jan 10, 2021 5:26 pm
Forum: General Science Questions
Topic: material
Replies: 4
Views: 23

### Re: material

In lecture, I remember Dr. Lavelle saying how not many concepts from 14A will appear directly. One that will appear again is lewis structures. Thermodynamics and some other topics are very different from 14A material.
Sun Jan 10, 2021 5:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Counting Moles
Replies: 11
Views: 46

### Re: Counting Moles

It helps to visualize this as well. If you increased pressure on a solid, it wouldn't change. Same with a liquid, it wouldn't change volume. However, if you increase pressure substantially on a liquid, it could turn to a solid.
Sun Jan 10, 2021 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling hw 5
Replies: 14
Views: 78

### Re: Sapling hw 5

The equations that have only unrelated compounds, such as the last equation, would not be useful. The extra equations were added to make the problem more difficult- you have to find the equations that could be added to get the reaction you want.
Sun Jan 10, 2021 5:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chemical Equilibrium Module 4 #13
Replies: 1
Views: 14

### Re: Chemical Equilibrium Module 4 #13

For the first one, when volume is compressed, that means that, since the moles stay the same, the concentration increases. Therefore, you shift towards the side that has less moles of gas. The reactant side has 3 moles of gas, and the products have 2 moles of gas. For the second one, the reaction is...
Fri Jan 08, 2021 11:45 pm
Forum: Ideal Gases
Topic: Ideal Gas
Replies: 3
Views: 15

### Re: Ideal Gas

With ideal gasses, you assume that there are no attractive forces taking place between molecules, the volume is negligible, the particles are constantly in motion, and all collisions are elastic. Essentially, the particles only have kinetic energy and no potential energy.
Sat Dec 12, 2020 6:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: heme complex shape
Replies: 2
Views: 34

### Re: heme complex shape

Adding to Mohamed's answer, the heme complex can bind to oxygen and histidine, indicating that it has 6 e- density regions.
Sat Dec 12, 2020 6:26 pm
Forum: Calculating the pH of Salt Solutions
Topic: Questions About Organizing Solutions by pH
Replies: 2
Views: 34

### Re: Questions About Organizing Solutions by pH

I think (not exactly sure) that in some cases like strong acids/bases, solutions that are negatively charged are acidic and positively charged are basic. This would be because when acids dissociate, the products will be an anion and H+ ion. The anion will make the solution negative. The same reasoni...
Sat Dec 12, 2020 6:12 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Dino Nuggets Question 13c
Replies: 2
Views: 41

### Re: Dino Nuggets Question 13c

I think you should have the right answer if you change grams to kilograms!
Fri Dec 11, 2020 8:29 pm
Forum: Polyprotic Acids & Bases
Topic: Acid Rain
Replies: 3
Views: 60

### Re: Acid Rain

Acid rain is caused by the reaction of carbon dioxide with water, which produced carbonic acid. Therefore, anything that reduces carbon dioxide in the air could reduce acid rain. An example would be switching to more renewable energy sources and burning less fossil fuels.
Fri Dec 11, 2020 8:22 pm
Forum: Coordinate Covalent Bonds
Topic: Definition
Replies: 4
Views: 35

### Re: Definition

From the lectures, a ligand is a lewis base that forms coordinate covalent bonds with a transition metal cation. That's all I have in my notes for the definition!
Sun Dec 06, 2020 11:41 am
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 9
Views: 66

### Re: Naming Coordination Compounds

-ate is added when the coordination complex has an overall negative charge.
Sun Dec 06, 2020 11:39 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy levels
Replies: 4
Views: 46

### Re: Energy levels

If this happened on the final and it was because you mixed up final and initial, you could also just reread the problem and look at whether the energy level needs to be above or below n=4. Because light was emitted, the answer should be n>4.
Sun Dec 06, 2020 11:31 am
Forum: Naming
Topic: what does (en) mean?
Replies: 23
Views: 155

### Re: what does (en) mean?

emilyyribarren1k wrote:Will we need to have this memorized? Also does anyone know if we can use the common ligand table on the final or if this type of information will be given to us in the question?

I know that the final is closed book, so I'm preparing to only get a periodic table and formula sheet.
Sun Dec 06, 2020 11:24 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Structure Names
Replies: 5
Views: 56

### Re: Structure Names

For octahedral, when you create a shape out of the atoms, making each one a vertex, then you get an octahedron. This shape has 8 faces, hence the name. If you look up the shape online, it will make more sense!
Sun Nov 29, 2020 11:48 pm
Forum: Dipole Moments
Topic: Dipole arrows
Replies: 8
Views: 46

### Re: Dipole arrows

Dipole arrows represent the dipole moment in a molecule. The arrow points towards the more electronegative atom. For example, water has an arrow pointing towards the oxygen in between the hydrogens representing the net dipole moment.
Sun Nov 29, 2020 11:41 pm
Forum: Bond Lengths & Energies
Topic: LDF Bond Strength
Replies: 11
Views: 91

### Re: LDF Bond Strength

The more electrons there are, the more electron shielding there is. Therefore, another molecule will more easily distort (or pull) the electrons in the large molecule, creating greater LDF's.
Sun Nov 29, 2020 11:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Names and Degrees
Replies: 4
Views: 28

### Re: Shape Names and Degrees

For memorizing the shapes, it's helpful to visualize them in a way that connects to their name. For example, it helps me to visualize trigonal bipyramidal as a triangle formed by 3 atoms and the other 2 atoms are the tips of 2 pyramids. This is much more useful than thinking of the regular lewis str...
Sun Nov 29, 2020 11:26 pm
Forum: Student Social/Study Group
Topic: Happy Thanksgiving!
Replies: 38
Views: 284

### Re: Happy Thanksgiving!

Happy Thanksgiving (3 days late)! My aunt usually makes potstickers as an appetizer!
Sun Nov 29, 2020 11:22 pm
Forum: Hybridization
Topic: How to simply determine hybridization
Replies: 27
Views: 185

### Re: How to simply determine hybridization

All you have to do is count the number of atoms bonded to that atom, and add this number to the number of lone pairs. sp corresponds to 2, sp2 to 3, and so on.
Thu Nov 19, 2020 8:24 pm
Forum: Octet Exceptions
Topic: Radical Unpaired Electron
Replies: 4
Views: 35

### Re: Radical Unpaired Electron

I think (not sure) it would be better to put the unpaired electron on the oxygen because the formal charge on both O and Cl would be 0. However, if the unpaired e- was on Cl, then Cl would have FC= +1 and O's FC= -1. This is less favorable.
Thu Nov 19, 2020 8:01 pm
Forum: Ionic & Covalent Bonds
Topic: HW Q 2A.17 Question about Valence Electrons
Replies: 3
Views: 31

### Re: HW Q 2A.17 Question about Valence Electrons

For valence electrons, you only want to count the number of electrons after the last noble gas' configuration. For this example, you would look at the e- configuration [Ar]3d3. Therefore, the textbook answer would make more sense!
Thu Nov 19, 2020 7:57 pm
Forum: Ionic & Covalent Bonds
Topic: Rules of ionization energy
Replies: 18
Views: 118

### Re: Rules of ionization energy

The general trend is that ionization energy increases up and across the periodic table.
Thu Nov 19, 2020 7:55 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration exceptions
Replies: 7
Views: 64

### Re: Electron configuration exceptions

In the notes, the only exceptions are Cr and Cu. But, it makes sense that Ni would want to fill its d orbitals as well. I think you could write Ni's electron configuration both ways. Also, for the Ni2+ cation, the highest energy electrons will be lost first. Therefore, the 4s electrons will be lost ...
Thu Nov 19, 2020 8:54 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: H-bonding
Replies: 5
Views: 56

### H-bonding

How many possible hydrogen bonding sites does guanine have? I think it's 11, but I want to be sure. Thanks!
Thu Nov 19, 2020 8:47 am
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energy
Replies: 3
Views: 39

### Re: Interaction Potential Energy

Interaction potential energy is the 2 polarizabilities of each molecule/atom multiplied together and divided by distance^(6). This equation means that when polarizability increases, the strength of the attractive interactions increases. Also, when distance increases, the interaction strength decreas...
Thu Nov 19, 2020 8:41 am
Forum: Resonance Structures
Topic: Resonance Hybrids
Replies: 2
Views: 41

### Re: Resonance Hybrids

Your'e correct! The resonance hybrid is an average of all the individual resonance structures drawn for a molecule. Resonance hybrids are more accurate than resonance structures because the represent bond lengths better. In any molecule that has more than one type of bond and has resonance structure...
Sun Nov 15, 2020 3:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What is effective nuclear charge?
Replies: 1
Views: 15

### Re: What is effective nuclear charge?

Looking back at notes, it was mentioned towards the end of lecture 10. It is the net positive charge on an electron in an atom. Inner electrons will shield outer electrons from the electrostatic attraction of the nucleus (+). Therefore, outer electrons feel reduced electrostatic attraction, and this...
Sat Nov 14, 2020 10:34 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.13: e- configuration for Silver (Ag)
Replies: 3
Views: 18

### Re: Textbook 1E.13: e- configuration for Silver (Ag)

A full 4d subshell is a more stable electron configuration. The 4d subshell is lower in energy than the 5s subshell, so the new e- configuration is lower in energy.
Fri Nov 13, 2020 8:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s orbital
Replies: 1
Views: 22

### Re: 3d and 4s orbital

Yes, if you are dealing with copper or chromium, they will have more stable electron configurations with full or half-full 3d subshells. N=3 is lower in energy than n=4.
Fri Nov 13, 2020 8:06 pm
Forum: Lewis Structures
Topic: Recognizing lowest formal charge
Replies: 11
Views: 50

### Re: Recognizing lowest formal charge

I like to draw the lewis structure and make sure the electron count is correct first. Then, I'll find the formal charges and draw a new lewis structure if it lowers the formal charges. Hope that helps a little!
Fri Nov 13, 2020 8:01 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Textbook #3F1
Replies: 4
Views: 47

### Re: Textbook #3F1

SO2 has a bent shape, which I believe causes it to be slightly polar and have dipole-dipole forces. Also, to answer the second question, hydrogen bonds are actually a type of dipole-dipole force, so yes!
Sun Nov 08, 2020 10:34 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.13
Replies: 3
Views: 25

### Re: Textbook 1E.13

This is one of the exceptions to writing electron configurations (the other is a d^5 subshell). Having a full 4d^10 subshell has a lower energy and is thus more stable than having a 4d^9 subshell. Another example of when this occurs is with copper and chromium.
Sun Nov 08, 2020 10:25 pm
Forum: Trends in The Periodic Table
Topic: Elements that form Cations
Replies: 6
Views: 24

### Re: Elements that form Cations

An easy way to think about this is to ask yourself what the easiest way to get to a full valence shell is. Would it be more simple to lose or gain electrons? For example, for +1 cations, it is much easier to lose one electron than to gain seven electrons.
Sat Nov 07, 2020 3:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground state electron configuration
Replies: 2
Views: 16

### Re: Ground state electron configuration

It also depends on the ion. If you're talking about a cation, then it lost electrons so there are less electrons than in the neutral state configuration. If you're talking about an anion, then it gained electrons so there are more electrons than in the neutral state configuration.
Sat Nov 07, 2020 3:33 pm
Forum: Ionic & Covalent Bonds
Topic: Salts v. Ionic bonds
Replies: 9
Views: 35

### Re: Salts v. Ionic bonds

I believe that all salts have ionic bonds. Any compound with an anion and cation is labeled as an ionic compound/salt.
Sat Nov 07, 2020 3:29 pm
Forum: Trends in The Periodic Table
Topic: Atomic radius when changing sub- shells
Replies: 4
Views: 19

### Re: Atomic radius when changing sub- shells

No, the atomic radius gets smaller which the last post explains. The exception, however, is that the radius increases from the nitrogen atom to the oxygen atom because of the extra electron-electron repulsion. Oxygen has 2 electrons in one orbital, whereas nitrogen does not.
Sun Nov 01, 2020 6:50 pm
Forum: Student Social/Study Group
Topic: Halloween!!!
Replies: 54
Views: 332

### Re: Halloween!!!

Happy day-after Halloween! I did scary clown makeup and hung out with a couple close friends and cousins. We ordered pizza and set up a projector in my backyard to watch the Nightmare on Elm Street!
Sun Nov 01, 2020 6:46 pm
Forum: Quantum Numbers and The H-Atom
Topic: electrons in an atom
Replies: 2
Views: 23

### Re: electrons in an atom

L indicates the particular subshell. 0 corresponds to s, 1 corresponds to p, and so on. If you know the values for l and n, then you know how many electrons are possible for that atom. For example, if l=2, then you know the atom reaches the d subshell. You then know that there are 5 orbitals for the...
Sun Nov 01, 2020 6:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Chromium Ions
Replies: 2
Views: 13

### Electron Configuration for Chromium Ions

Hi,

How would you write the electron configurations for the Chromium ions? Also, how do you write the electron configurations for cations in the d block in general?
Sun Nov 01, 2020 6:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: e- configuration exceptions
Replies: 2
Views: 38

### Re: e- configuration exceptions

These exceptions apply to chromium and copper. When writing chromium's electron configuration, you have [Ar]3d^(4)4s^(2). However, to get the lowest energy and therefore the most stable configuration, you want to put one electron from the 4s subshell into the 3d subshell so that there are 6 unpaired...
Sun Nov 01, 2020 6:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Question 26 Sapling
Replies: 5
Views: 60

### Re: Question 26 Sapling

Adding on to Charlene's answer, you can use the equation (uncertainty in momentum)=(mass)(uncertainty in velocity) to substitute for uncertainty in momentum in Heisenberg's Indeterminacy Equation. Therefore, you can get the final answer using only one equation.
Sat Oct 24, 2020 11:34 pm
Forum: Einstein Equation
Topic: Post Assement audio visual
Replies: 3
Views: 44

### Re: Post Assement audio visual

I may be wrong, but I believe the answer is middle option. You are correct that the work function is the energy required to remove an electron. You have to convert kJ/mol to J/photon. In order to do this, you can use conversion factors to convert kJ to J, then multiply this by (1 mol/ 6.02x10^23 pho...
Sat Oct 24, 2020 4:46 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling HOMEWORK #10
Replies: 2
Views: 28

### Re: Sapling HOMEWORK #10

If you draw 7 energy levels, you can visualize all of the possible changes in energy level. There are six levels below n=7, so there are 6 spectral lines that can appear. The wavelength range will be between the shifts of n=7 to n=6 and n=7 to n=1. The highest wavelength corresponds to the lowest en...
Sat Oct 24, 2020 4:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B.25 Second Part
Replies: 2
Views: 52

### 1B.25 Second Part

Hi, I am confused what to do in this problem:
Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom.

The diameter was given in the problem, then you can find the uncertainty in velocity, which I understand how to do. What would this model look like, though?
Sat Oct 24, 2020 4:03 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Equation Answers
Replies: 1
Views: 25

### Heisenberg Uncertainty Equation Answers

When we get the final answer using the Heisenberg Uncertainty Equation whether it is delta x or delta p or delta v, what does this value mean conceptually? Could someone please give an example of how you could apply the answer to a real world situation? I'm mostly confused about the inequality symbol.
Sat Oct 24, 2020 3:53 pm
Forum: Molarity, Solutions, Dilutions
Topic: Precipitation Reaction
Replies: 2
Views: 44

### Re: Precipitation Reaction

I think you should definitely know this just in case. It's a concept from high school chemistry- only the ions that are used to make the product and the precipitate are included in the net ionic equation. No spectator ions are included.
Sat Oct 17, 2020 4:19 pm
Forum: Properties of Electrons
Topic: Electron vs. X-ray Diffraction
Replies: 3
Views: 32

### Re: Electron vs. X-ray Diffraction

That's interesting, thank you!
Sat Oct 17, 2020 2:30 pm
Forum: SI Units, Unit Conversions
Topic: Textbook Practice Problem E15
Replies: 3
Views: 13

### Re: Textbook Practice Problem E15

This problem is asking you to find M(x)S(x), which is the metal sulfide. You know the molar mass of the metal by subtracting the molar masses of 2 oxygen and 2 hydrogen atoms from 74.10 g/mol. You also know the charge is +2 because hydroxide is -1, and there are two hydroxide ions. Then, the sulfide...
Sat Oct 17, 2020 2:12 pm
Forum: Properties of Electrons
Topic: Electron vs. X-ray Diffraction
Replies: 3
Views: 32

### Electron vs. X-ray Diffraction

In yesterday's lecture, Dr. Lavelle mentioned that x-ray diffraction is easier to use/more available than electron diffraction. Why is this, and what is the difference in results when using these two methods?
Thu Oct 15, 2020 2:40 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question during Lecture on 10/14
Replies: 4
Views: 40

### Re: Question during Lecture on 10/14

Electrons are not emitted when they transition between energy levels. The arrow he drew going down represents an excited electron moving back to ground state. This will emit a specific amount of energy; every atom and molecule has unique amounts of energy they absorb/emit, and electrons never stay b...
Thu Oct 15, 2020 11:53 am
Forum: Properties of Electrons
Topic: Ephoton > or = to Eremove(e-)
Replies: 7
Views: 81

### Re: Ephoton > or = to Eremove(e-)

It was just that the wording was a little confusing. He meant that when the energy of the photon is greater than or equal to the energy to remove an electron, electrons are emitted. All other times, electrons are not emitted.
Wed Oct 14, 2020 12:36 pm
Forum: Properties of Light
Topic: Amplitude/Intensity and Number of Photons
Replies: 2
Views: 49

### Re: Amplitude/Intensity and Number of Photons

Hi! Adding on to this, I think the most important concept to know is that increasing the intensity of light does increase the number of photons, but if no electrons are being ejected to begin with, this will not result in ejected electrons. One photon can eject one electron, so the energy of each ph...
Thu Oct 08, 2020 7:01 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution Question
Replies: 5
Views: 59

### Re: Dilution Question

Thanks everyone!
Thu Oct 08, 2020 1:41 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution Question
Replies: 5
Views: 59

### Dilution Question

I am not sure how to solve this question, a quick walkthrough would be appreciated:

How many mL of water would you need to add 40.0 mL of .20 M HCl to achieve a 1/5 dilution?

Wed Oct 07, 2020 11:35 am
Forum: Balancing Chemical Reactions
Topic: Fractions
Replies: 26
Views: 169

### Re: Fractions

I believe we are supposed to use whole numbers only for the final answer. So if you had 3/2 as a stoichiometric coefficient, you would need to multiply every coefficient by 2.
Tue Oct 06, 2020 11:42 am
Forum: Limiting Reactant Calculations
Topic: Textbook Question M19)
Replies: 5
Views: 61

### Re: Textbook Question M19)

Forgot to mention that subtracting all the masses from caffeine gives you the mass of oxygen.
Tue Oct 06, 2020 11:41 am
Forum: Limiting Reactant Calculations
Topic: Textbook Question M19)
Replies: 5
Views: 61

### Re: Textbook Question M19)

First, you need all the masses of each element- C, H, N, and O. Convert grams of carbon dioxide to grams of carbon using conversion factors, and do the same for hydrogen in water. Now you have the masses of C, H, and N, so you can add all these masses together and subtract it from the total mass of ...
Tue Oct 06, 2020 11:24 am
Forum: Limiting Reactant Calculations
Topic: Sapling Homework #10
Replies: 7
Views: 74

### Re: Sapling Homework #10

I know we haven't gone over it, but the picture showed the molecular formula. Each corner represents a carbon. There were 4 carbons, so you could redraw it as a lewis structure and go from there. I checked online as well!
Mon Oct 05, 2020 1:54 pm
Forum: SI Units, Unit Conversions
Topic: E1
Replies: 5
Views: 76

### Re: E1

You have to multiply the number of molecules, which is 6.02e23 molecules of Ag by 144 pm. This gives you the total distance.
Mon Oct 05, 2020 1:45 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals Problem E15
Replies: 4
Views: 44

### Re: Fundamentals Problem E15

So to do this you first can find the charge of the metal. Since there are 2 OH- ions, then the cation is M^(+2). Then, you can find the molar mass of the 2 hydroxides and subract this from the total molar mass. This gives you the mass of the metal. The sulfide ion is S^(-2), so you would assume the ...

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