Search found 66 matches

by EvanWang
Tue Jan 21, 2020 9:10 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Increase in Pressure
Replies: 1
Views: 6

Re: Increase in Pressure

An increase in pressure by compression of the system will favor the side of the reaction with fewer moles of gas. This is because when you reduce the volume of the system (via compression) then the concentrations are increased, and the reaction quotient shifts above or below K. This shift in Q resul...
by EvanWang
Tue Jan 21, 2020 9:05 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Second Ionization in Polyprotic Acid Solutions
Replies: 2
Views: 9

Re: Second Ionization in Polyprotic Acid Solutions

For most polyprotic acids except sulfuric acid, the second ionization contributes so few H3O+ that its effect on pH is negligible.
by EvanWang
Mon Jan 20, 2020 9:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure goes to less moles of gas explaination
Replies: 4
Views: 8

Re: Pressure goes to less moles of gas explaination

He explained that if pressure is increased by decreasing volume (if a piston pushed down on the reaction, for example) then the concentration of each of the gases in the reaction would increase. We calculate concentration by using \frac{n}{V} where n is moles of gas and V is the volume of the contai...
by EvanWang
Mon Jan 20, 2020 9:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas
Replies: 4
Views: 14

Re: Inert Gas

Although adding an inert gas affects the total volume of the reaction, they do not interact with anything, thus causing there to be no change in concentration. I thought the whole point was that adding a inert gas doesn't affect the volume of the container, which was why it has no affect on concent...
by EvanWang
Mon Jan 20, 2020 9:15 pm
Forum: Polyprotic Acids & Bases
Topic: Deprotonation
Replies: 3
Views: 12

Re: Deprotonation

Typically the Ka for the second deprotonation is extremely small. Apart from sulfuric acid, for most acids it doesn't have a meaningful effect on pH.
by EvanWang
Thu Jan 16, 2020 6:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negative pH
Replies: 6
Views: 18

Re: Negative pH

Yes, pH can be negative and it just means that the molarity of H+ is greater than 1. Google tells me that some acids have been observed at pH -18.
by EvanWang
Thu Jan 16, 2020 11:41 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units in ICE Table
Replies: 8
Views: 35

Re: Units in ICE Table

The values of the ICE table must be in concentration because they will be calculated using Kc, which deals with concentrations.
by EvanWang
Thu Jan 16, 2020 11:37 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure (5J.1)
Replies: 3
Views: 9

Re: Partial Pressure (5J.1)

I have another similar question with 5J.3 - can someone explain why adding/removing a certain amount of a compound might affect its equilbrium? Adding or removing a certain amount of compound will not affect the equilibrium constant K because only temperature will do that. It will affect the equili...
by EvanWang
Thu Jan 16, 2020 11:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure (5J.1)
Replies: 3
Views: 9

Re: Partial Pressure (5J.1)

When looking at problems like this, it is a good idea to keep the equation for K in mind. According to that equation, if one product increases the other products must decrease to keep the same ratio of K. Additionally, if one reactant increases then the products must increase to keep the same ratio ...
by EvanWang
Thu Jan 16, 2020 11:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka and Kb
Replies: 5
Views: 12

Re: Ka and Kb

K B and K A are calculated the same way. From what I gathered from the lecture, K B has to do with the equilibrium constant of bases and has [OH - ] as a product. Conversely, K A has to do with the equilibrium constant of acids and has [H 3 O + ] as a product. That's the extent to how much they diff...
by EvanWang
Thu Jan 16, 2020 11:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Factos effecting Equilibrium
Replies: 6
Views: 10

Re: Factos effecting Equilibrium

Temperature is the only thing that affects the equilibrium constant k. Factors such as concentrations of species, partial pressures of species, and volume of the container can all affect the reaction quotient, q, and drive the reaction in a certain direction in order to achieve equilibrium again.
by EvanWang
Thu Jan 09, 2020 8:26 pm
Forum: Administrative Questions and Class Announcements
Topic: Solutions Manual
Replies: 4
Views: 26

Re: Solutions Manual

You can find the solutions manual at Powell Library. It is on hold for this class, and every time I check it out it has been available. Just ask the help desk and have your Bruin Card on hand.
by EvanWang
Thu Jan 09, 2020 8:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc and Kp
Replies: 4
Views: 17

Re: Kc and Kp

Kc is used for concentration in general, it applies to aqueous solutions and gases. Kp applies to partial pressures of gases.
by EvanWang
Thu Jan 09, 2020 8:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Catalyst and Equilibrium
Replies: 2
Views: 11

Re: Catalyst and Equilibrium

A catalyst speeds up a reaction but is not used during it, it is neither a product nor a reactant. It doesn't affect the concentrations of product or reactant at equilibrium.
by EvanWang
Thu Jan 09, 2020 8:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 10
Views: 44

Re: Units for K

K is technically calculated using an attribute called the activity of a substance, and activity is unitless.
by EvanWang
Thu Jan 09, 2020 8:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating K
Replies: 6
Views: 29

Calculating K

In a reaction where the only substance that can be inputed into K is on the reactant side (the rest of the reactants and products are either solids or pure liquids), is K calculated as just the concentration of that substance? Or is it the inverse of the concentration?
by EvanWang
Fri Nov 29, 2019 9:15 pm
Forum: Naming
Topic: Polydentate Ligands
Replies: 3
Views: 42

Re: Polydentate Ligands

It's tough to say but generally the bonding sites should be on the same side of the molecule. For example, cisplatin works because both of the Chlorines are on the same side and can bind to DNA at two points. If the Chlorines were in an orientation where they were opposite each other, the resulting ...
by EvanWang
Fri Nov 29, 2019 9:08 pm
Forum: Bronsted Acids & Bases
Topic: Strong acids and bases
Replies: 2
Views: 17

Re: Strong acids and bases

I would study the strong acids and bases, as well as the trends in what makes an acid/base strong or weak.
by EvanWang
Fri Nov 29, 2019 6:18 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted base
Replies: 3
Views: 23

Re: Bronsted base

In the following reaction:
HCl(aq)+NH3(aq)→NH+4(aq)+Cl−(aq)

The NH3 accepts H+ ions donated from the HCl. That makes it a bronsted base.
by EvanWang
Fri Nov 29, 2019 6:08 pm
Forum: Hybridization
Topic: Writing the hydrization
Replies: 10
Views: 80

Re: Writing the hydrization

I think it wouldn't hurt to specify the principle quantum number when you know what the central atom is. If you only know the areas of electron density around the central atom, then you can only discern the hybridization without the principle quantum number.
by EvanWang
Fri Nov 29, 2019 5:54 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg
Replies: 4
Views: 37

Re: Rydberg

A photon is absorbed when the energy of an electron increases and its principle quantum number increases. The energy is positive when a photon is absorbed.
by EvanWang
Tue Nov 19, 2019 1:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear Shape
Replies: 6
Views: 33

Re: Linear Shape

Only if the bonded atoms on either side of the central atom are the same will the molecule be nonpolar. If the bonded atoms are different, there will be a net dipole moment.
by EvanWang
Tue Nov 19, 2019 1:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 30

Re: Bond Angles

In most cases when there is a lone pair, the actual bond angles are less than the expected for the electron arrangement. This is because lone pairs are more diffuse than bonding atoms, in other words they take up more space. As a result, they push the bonding atoms away more than a bonding atom woul...
by EvanWang
Tue Nov 19, 2019 1:14 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: Types of forces
Replies: 4
Views: 30

Re: Types of forces

It does not mention that there are other ions around, therefore there are no ion-dipole forces. Also, the question does not mention that there are other nonpolar molecules around, so there are no dipole-induced dipole forces.
by EvanWang
Tue Nov 19, 2019 1:10 pm
Forum: Dipole Moments
Topic: Elongated vs. Spherical Molecules
Replies: 3
Views: 31

Re: Elongated vs. Spherical Molecules

The molecular formulas of organic molecules will typically be written in sections. If a molecule has many sections, such as CH3(CH2)3CH3, then it will be elongated. A molecule written like C5H12, is spherical. Notice how they have the same amounts of C and H atoms, but they are written in a way that...
by EvanWang
Tue Nov 19, 2019 1:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Bipyramidal
Replies: 1
Views: 20

Re: Trigonal Bipyramidal

If all the equatorial atoms are the same, you can break the dipole vectors into their component vectors and you will see that they all cancel. The axial atoms are pointed 180 degrees apart, so their dipoles cancel.
by EvanWang
Tue Nov 19, 2019 1:01 pm
Forum: Lewis Structures
Topic: H2SeO4
Replies: 2
Views: 40

Re: H2SeO4

The lewis structure where Se is surrounded by four oxygens allows for all the formal charges to be zero when two of the oxygens double-bond with Se and the other two oxygens single bond with Se and H. The lewis structure where the two hydrogens bond with the central Se atom doesn't allow for all for...
by EvanWang
Tue Nov 19, 2019 12:56 pm
Forum: Dipole Moments
Topic: Polar/Nonpolar Molecule Question
Replies: 2
Views: 20

Re: Polar/Nonpolar Molecule Question

If you draw the molecule out, it will look like 2 C 2 H 5 groups bonded on either side of a central oxygen atom. The oxygen can only single bond with both of the carbons next to it because the carbons already have three bonds. This leaves the central oxygen atom with two bonding pairs and two lone p...
by EvanWang
Tue Nov 19, 2019 12:51 pm
Forum: Bond Lengths & Energies
Topic: Boiling point
Replies: 11
Views: 74

Re: Boiling point

If a problem strictly mentions molar mass, or states that there are no dipole-dipole interactions or hydrogen bonding, then increasing molar mass increases the Van de Waal forces because larger molecules can have larger instantaneous dipole moments. Larger Van de Waal forces means more attraction be...
by EvanWang
Tue Nov 19, 2019 12:49 pm
Forum: Hybridization
Topic: How to do 2.F.7?
Replies: 1
Views: 15

Re: How to do 2.F.7?

You determine the hybridization of orbitals by the number of areas of electron density around a central atom. Areas of electron density include bonding pairs and lone pairs. If there are n number of areas of electron density, you need n number of hybridized orbitals.
by EvanWang
Tue Nov 19, 2019 12:45 pm
Forum: Hybridization
Topic: hybridization
Replies: 11
Views: 57

Re: hybridization

Look at the lewis structure to help figure out the hybridization of an atom. If a central atom has four areas of electron density around it, then you need a hybridization that corresponds to those four areas. In this case, sp 3 . If an atom has three areas of electron density, the hybridization is s...
by EvanWang
Tue Nov 19, 2019 12:42 pm
Forum: Dipole Moments
Topic: NH2OH
Replies: 2
Views: 18

Re: NH2OH

The overall shape of the molecule is not not symmetrical, there is a net dipole moment because the dipoles are not equal in magnitude and in opposite directions.
by EvanWang
Tue Nov 19, 2019 12:39 pm
Forum: Hybridization
Topic: test 2
Replies: 6
Views: 48

Re: test 2

According to my TA hybridization won't be on the test, but it wouldn't hurt to know since it explains the behavior of some of the topics mentioned on the test.
by EvanWang
Tue Nov 19, 2019 12:37 pm
Forum: Dipole Moments
Topic: Polar or nonpolar
Replies: 8
Views: 67

Re: Polar or nonpolar

O2 is nonpolar because it is two of the same atom, there is no net dipole moment because both oxygens "pull" on electrons the same amount in opposite directions.
by EvanWang
Tue Nov 19, 2019 12:34 pm
Forum: Hybridization
Topic: What are pi bonds in relation to sigma?
Replies: 2
Views: 16

Re: What are pi bonds in relation to sigma?

Pi bonds form in cases where there is one or more p orbitals that have not been hybridized into an spn orbital. These leftover p orbitals are able to form a pi bond by bonding perpendicular to the plane of the sigma bond.
by EvanWang
Sun Nov 10, 2019 11:43 pm
Forum: Electronegativity
Topic: Noble Gases
Replies: 19
Views: 149

Re: Noble Gases

I like to consider electronegativity as how much an atom will hog an electron when it is bonded. Since Neon already has an octet, it won't want any more electrons so, hypothetically, it will have very low electronegativity.
by EvanWang
Sun Nov 10, 2019 11:40 pm
Forum: Dipole Moments
Topic: Intermolecular Forces
Replies: 2
Views: 10

Re: Intermolecular Forces

Although nonpolar molecules may have symmetrical electron distributions, there are instances when one area of the molecule is more negative than the other. This fluctuating electron distribution results in fluctuating dipoles. Van der Waals forces are the results of those instantaneous dipoles that ...
by EvanWang
Sun Nov 10, 2019 11:31 pm
Forum: Dipole Moments
Topic: Representation
Replies: 1
Views: 13

Re: Representation

I think it is represented with an arrow with its tail beginning at the positive atom and pointing toward the negative atom.
by EvanWang
Sun Nov 10, 2019 11:30 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar vs covalent
Replies: 7
Views: 31

Re: Polar vs covalent

Covalent bonds occur between two nonmentals, while ionic bonds occur between a metal and a nonmetal.
by EvanWang
Sun Nov 10, 2019 11:27 pm
Forum: Dipole Moments
Topic: H Bonding
Replies: 4
Views: 27

Re: H Bonding

H bonding occurs with N, O, and F because those elements have high electronegativity. When they bond covalently with Hydrogen, they will hog the electrons more and make that part of the molecule partially negative and the hydrogen atom partially positive. While this can occur with other elements, th...
by EvanWang
Tue Oct 29, 2019 12:38 pm
Forum: Ionic & Covalent Bonds
Topic: Study For midterm
Replies: 7
Views: 54

Re: Study For midterm

I would look thoroughly through the topics discussed in the syllabus and try to do a problem pertaining to each one. Bring up questions you have with your TA and spread the studying out over several days.
by EvanWang
Tue Oct 29, 2019 12:33 pm
Forum: Lewis Structures
Topic: Homework problem 2C.3
Replies: 5
Views: 44

Re: Homework problem 2C.3

I asked my TA and he said that we aren't expected to know nomenclature right now, but I would try to memorize the important polyatomic ions like phosphate.
by EvanWang
Tue Oct 29, 2019 12:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Question 2A5
Replies: 3
Views: 34

Re: HW Question 2A5

It is energetically favorable for Cu to have a ground state electron configuration of [Ar]3d 10 4s 1 . This is because when the 4s shell is half-filled and the 3d shell is completely filled, the atom is more stable. When you take away an electron, you take it away from the 4s shell because it is fur...
by EvanWang
Tue Oct 29, 2019 12:16 pm
Forum: Resonance Structures
Topic: stability
Replies: 2
Views: 29

Re: stability

Resonance allows for delocalization, in which one or more electrons are spread out evenly across all bonds. This lowers the overall energy of the molecule.
by EvanWang
Tue Oct 29, 2019 12:07 pm
Forum: Resonance Structures
Topic: hybrid structure
Replies: 4
Views: 35

Re: hybrid structure

No, resonance happens when you have the same arrangement of atoms, but different arrangements of electrons. For example, in ClO- the single bond could be in four different locations.
by EvanWang
Sun Oct 20, 2019 9:49 pm
Forum: DeBroglie Equation
Topic: Unit Conversion
Replies: 5
Views: 43

Re: Unit Conversion

The prefix Mega (M) in SI units always means 10^6. So 1 MHz is 1*10^6 Hz.
by EvanWang
Sun Oct 20, 2019 9:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configurations of ions
Replies: 4
Views: 22

Re: Electron configurations of ions

Elements that are closer to the left side of the periodic table generally give up electrons and elements on the right side of the periodic table generally take electrons. This is reflected in the increasing ionization energy going right to left across a period.
by EvanWang
Sun Oct 20, 2019 9:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions within P.t.
Replies: 2
Views: 21

Re: Exceptions within P.t.

In addition to the half-filled 4s orbital lending more stability, a completely full 3d orbital is more stable than one that is partially filled. If I remember correctly, Dr. Lavalle also said something about the 3d orbital having slightly less energy than the 4s orbital, but I'm not sure if that has...
by EvanWang
Sun Oct 20, 2019 9:23 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Noble Gases in Electron Configurations
Replies: 6
Views: 24

Re: Noble Gases in Electron Configurations

In addition to what everyone else said, I think it's because the noble gasses don't react much and are very stable, much like the innermost electrons that they represent.
by EvanWang
Sun Oct 20, 2019 9:20 pm
Forum: Properties of Electrons
Topic: Absorption and Emission Spectra of Electrons
Replies: 1
Views: 39

Absorption and Emission Spectra of Electrons

When a wavelength of light is absorbed in the UV (Lyman) region, then can we assume that n i is 1? And for wavelengths of light emitted that correspond to the Lyman series, can we assume that n f is 1? Or do we always assume that n f is 1 for regardless of whether the electron emits or absorbs a pho...
by EvanWang
Wed Oct 16, 2019 7:53 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Homework Problem Help
Replies: 5
Views: 48

Re: Homework Problem Help

An orbital must have 3 quantum numbers, and no two orbitals can have the same quantum numbers. Knowing this, b and d both indicate only 1 orbital because they list 3 quantum numbers. For a and c, since all 3 quantum numbers are not given we must list the other possible numbers to find the number of ...
by EvanWang
Wed Oct 16, 2019 5:41 pm
Forum: DeBroglie Equation
Topic: De Broglie Wavelength
Replies: 7
Views: 49

Re: De Broglie Wavelength

I think it just means to use the De Broglie equation because the De Broglie equation is derived from the equations E=pc, c= wavelength*frequency, and E=hv which we have learned before. However, this equation only works for any particle with a rest mass, momentum, and wavelength so if it asks for th...
by EvanWang
Wed Oct 16, 2019 5:36 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals Problem Question
Replies: 1
Views: 54

Re: Fundamentals Problem Question

This is a multistep reaction. You have to first balance both reaction equations. Next, you have to convert the amounts of phosphorus and oxygen into moles. Then, you use the mole ratio to find out which reactant will run out first. Phosphorus is the limiting reactant because it will run out first. O...
by EvanWang
Wed Oct 16, 2019 5:26 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D.25
Replies: 3
Views: 45

Re: 1D.25

When a question asks whether a certain orbital can exist, it is asking if the quantum numbers are possible. If we look at 6f as an example, Because: n=6 The possible values of l are: l=(0 to n-1) or 0,1,2,3,4,5 We know that the f subshell occurs when l=3. Since 3 is listed in the possible values of ...
by EvanWang
Wed Oct 16, 2019 5:20 pm
Forum: Properties of Electrons
Topic: Relationship between Speed and Frequency
Replies: 3
Views: 31

Re: Relationship between Speed and Frequency

We assume the speed of light to be constant, so any changes in frequency won't impact the speed of the wave. Also, only applies to particles with resting mass like electrons, not electromagnetic radiation.
by EvanWang
Wed Oct 09, 2019 1:02 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Light energy
Replies: 3
Views: 43

Re: Light energy

I think you just need to memorize the fact that visible light occurs between 400 and 700 nm.
by EvanWang
Wed Oct 09, 2019 12:58 pm
Forum: Properties of Light
Topic: Homework Problems
Replies: 3
Views: 39

Re: Homework Problems

The questions for 1A begin on page 9. The last question for 1F is on page 63.
by EvanWang
Wed Oct 09, 2019 12:53 pm
Forum: SI Units, Unit Conversions
Topic: Sig Fig Help! [ENDORSED]
Replies: 6
Views: 85

Re: Sig Fig Help! [ENDORSED]

1.0003 has 5 significant figures because the zeroes come between nonzero digits. 0.0003 only has 1 significant figure. This is because you can rewrite it as 3x10^-4 (which only has one sigfig). The leading zeroes are not significant even if they come after a decimal point.
by EvanWang
Wed Oct 09, 2019 12:49 pm
Forum: Empirical & Molecular Formulas
Topic: Writing Empirical Formulas
Replies: 8
Views: 105

Re: Writing Empirical Formulas

Generally, the order the elements are given in the problem will be the same order you can write them in your answer. In organic molecules, that normally means C, H, then everything else.
by EvanWang
Wed Oct 09, 2019 12:45 pm
Forum: Photoelectric Effect
Topic: Threshold energy
Replies: 6
Views: 44

Re: Threshold energy

Different elements have different threshold energies. If it's not given, you can always determine the threshold energy by using
Threshold energy=Energy of photon-kinetic energy of ejected electron
by EvanWang
Tue Oct 01, 2019 8:54 pm
Forum: Molarity, Solutions, Dilutions
Topic: Question on E27
Replies: 4
Views: 40

Re: Question on E27

You use the molar masses of oxygen and hydrogen to find the mass of one mole of water molecules. Next, divide that number by avogadro's constant to find the mass of one water molecule.
by EvanWang
Tue Oct 01, 2019 8:49 pm
Forum: Balancing Chemical Reactions
Topic: Question H7a
Replies: 6
Views: 48

Re: Question H7a

Calcium is in the second group of the periodic table so calcium ions are Ca2+. Hydroxide ions have a -1 charge, so you need 2 OH to make the overall charge neutral. So Calcium hydroxide is Ca(OH)2.
by EvanWang
Tue Oct 01, 2019 4:31 pm
Forum: Significant Figures
Topic: Sig Figs for Tests/Quizzes
Replies: 7
Views: 75

Re: Sig Figs

For sig figs, do we round to the correct number of sig figs at the end or do we constantly round to the correct number as we go? Generally, it is better to try to use exact values throughout the calculations and then round at the end. If your calculator has it, it could be helpful to save the exact...
by EvanWang
Tue Oct 01, 2019 4:23 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Accuracy and Precision [ENDORSED]
Replies: 4
Views: 81

Re: Accuracy and Precision [ENDORSED]

I don't think we need to calculate the level of precision and accuracy, we just need to identify situations and experimental results that are precise, accurate, both and neither.
by EvanWang
Tue Oct 01, 2019 4:21 pm
Forum: Properties of Light
Topic: Relationship Between Velocity and Wavelength
Replies: 6
Views: 109

Re: Relationship Between Velocity and Wavelength

I'm not entirely sure this is correct, but the only instance I've seen velocity and wavelength related is with the work-function equation. This is used to find the energy required to remove an electron from a metal:
E=1/2 m v^2=hv-Φ
1B in the textbook talks about this. Hope it helps.

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