CHEMISTRY COMMUNITY

Gerald Bernal1I

Kc is used if you are given concentrations and Kp is used when you are given partial pressures.

Gerald Bernal1I

for which equation?

Gerald Bernal1I

If the graph of [A] v. time is a negative slope straight line. Other than that you find the order of a reaction through experimental data. Zero orders do not affect the reaction rate and therefore Rate=k.

Gerald Bernal1I

Its the side whose reaction does not already involve a solid metal and therefore platinum is added as an electrode to conduct the reaction.

Gerald Bernal1I

For finding standard Gibbs free energy formations and standard reduction reaction values, would we just have to use the textbook? The constant and equation sheet does not have the same amount of resources than the one we received on the midterm.

Gerald Bernal1I

Its the rate determining step unless it does not match up with the actual rate law of the reaction.

Gerald Bernal1I

You do not flip the sign if you are calculating the standard cell potential for the anode value.

Gerald Bernal1I

The nernst equation is used to calculate the cell potential anytime the cell is not in standard conditions. It can be applied to galvanic cells, concentration cells, electrolytic cells. As long as the number of electrons transferred and the standard cell potential is known, it can be used.

Gerald Bernal1I

You would get the H+ concentration from the pH and then use that as the change in your ice table. The problem gives you the initial concentration of the acid and if you subtract that from the H+ concentration you get the equilibrium concentration for HF. Input these values into the Ka equilibrium eq...

Gerald Bernal1I

Any problem that mentions trying to find the activation energy.

Gerald Bernal1I

Anode is where the oxidation half reaction of the redox reaction takes place and cathode is where the reduction half reaction takes place. Since the oxidation in the solution of the anode is losing electrons, these electrons travel through the anode which is a solid metal to the cathode another soli...

Gerald Bernal1I

For electrolytic cells, the cathode is still the reaction getting reduced and the anode is the reaction being oxidized. You would still use the reduction cell potentials given but you will notice that when you calculate Ecell= E cathode -E anode you get a negative cell potential which further emphas...

Gerald Bernal1I

The number of electrons exchanged should not change once the redox reaction is balanced.

Gerald Bernal1I

K is the equilibrium constant and therefore used at equilibrium. Q is used whenever the equation is not at equilibrium or when initial concentrations are given rather than equilibrium concentrations.

Gerald Bernal1I

The reducing agent is the substance being oxidized since it is reducing the reduction reaction. The oxidizing agent is the substance undergoing reduction since its reduction or gain of electrons is causing the loss of the oxidation.

Gerald Bernal1I

Table 4.J.1 explains how these are related in different conditions. The relationship with all three is factoring in a systems entropy, enthalpy and temperature values in order to give the energy of the system.

Gerald Bernal1I

If the reaction does not have a solid metal included, then you add platinum to either side of the cell diagram. However, like he showed in class today, the equation had a solid metal for only one reaction and therefore Copper solid was used to conduct the anode and the cathode having no conductor, p...

Gerald Bernal1I

Wmax is related to deltaG when Temperature and Pressure are constant since those are the conditions that need to be met for Gibbs free energy.

Gerald Bernal1I

Finding the half reactions shouldn't be any different, but when you have OH- you do neutralize it by adding an H to the opposite side. However, the homework problem just ends up using the reaction of O2 given in the Table 6.M.1

Gerald Bernal1I

The oxidation state of oxygen will always be -2.

Gerald Bernal1I

Reversible means the system is in equilibrium with the surroundings. Whatever happens to the surroundings will therefore affect the system. When it is irreversible it is not in equilibrium.

Gerald Bernal1I

It has to do with the Vant Hoff equation relating the equilibrium constant with spontaneity. Therefore, when the K value changes, so does the spontaneity of the reaction process.

Gerald Bernal1I

Vant Hoff equation problems and I imagine some redox reaction problems would be accepted. He only introduced electrochemistry recently so I think any remaining thermochemistry or thermodynamic problems are fine.

Gerald Bernal1I

His syllabus says he does not curve, but I imagine there would only be a curve if a very low number of people pass on an exam.

Gerald Bernal1I

This equation relates equilibrium constant with Gibbs free energy. The $G^{\circ}$ refers to finding the G value when the reactants and products are in their standard states.

Gerald Bernal1I

pH is always calculated when the equation is at equilibrium. When pH is given it means that the H+ from the pH is the H+ value at equilibrium.

Gerald Bernal1I

G knot just means that it is only applicable when the elements in the equation are in their standard state since the knot denotes that it is the Gibbs free energy value at standard state.

Gerald Bernal1I

Is the equation $\Delta S= qrev/T$ only used to find entropy of the surroundings or is it used to find the entropy of the system?

Gerald Bernal1I

Hf is used for standard enthalpy of formation for all equations, but Hc denotes enthalpy of combustion. This value would be helpful for a Hess's law calculation that is typical of combustion reactions.

Gerald Bernal1I

The second law explains entropy in regards to a system. The total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. This is used describe spontaneity in a system or if a reaction is favorable. The equations dealing with entropy h...

Gerald Bernal1I

Cv and Cp are used only for gases to find their change of internal energy. There are calculation differences since gases are compressible and their Cp and Cv value will not be the same. Liquids and solids do not have these and we assume they have only one specific heat since they are incompressible.

Gerald Bernal1I

The standard enthalpy of formation is the change in enthalpy when one mole of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its pure elements under the same conditions. The standard enthalpy of reaction takes these values and calculates the heat given off or taken...

Gerald Bernal1I

Phase change is taken into account when the matter is changing phase. For examples if a problem asks to find the energy from boiling water when you started at a certain temperature. You would calculate q=mc(Tf-Ti) and use the specific heat and then add the heat of vaporization energy which does not ...

Gerald Bernal1I

They only differ in the units they use but they essentially calculate the same thing. Like example earlier in lecture, Lavelle used the molar heat capacity since the problem gave the substance in mol.

Gerald Bernal1I

Hess's law uses the step equations or reactions along with the energy transferred in each reaction to give you the overall delta H. It shows that enthalpy is a state function since it does not matter how many steps in between give the overall reaction since it will add up to the enthalpy of the over...

Gerald Bernal1I

In order for a phase change to happen enough heat or energy has to be applied to overcome the phase and then the bond. That is why when you use the second method you add the heat of fusion or vaporization to the bond enthalpy to get the enthalpy of the reaction.

Gerald Bernal1I

The only formula on the Constants and equations sheet is the third method equation. The rest will probably have to be memorized.

Gerald Bernal1I

They should all give you the net enthalpy or Hf. You should use them based on what information a question gives you.

Gerald Bernal1I

The last method was just describing using the summation of the enthalpy of the products minus the summation of the reactants enthalpy will give you the overall enthalpy of the reaction. So it would be the moles of the reactants times their formation enthalpies (i.e. CH4+ 2O2 --> CO2+ 2H2O for summat...

Gerald Bernal1I

The protonation being less than 5% guarantees that the assumption to neglect X because the change is so small so you should not have to use the quadratic.

Gerald Bernal1I

To find the desired pH you just use the desired concentration 0.025 and you get pH of 1.6. To get the actual solution pH you multiply the molarity by the 0.200 L volume in order to find the desired moles and divide that by 0.250 L to get the new molarity/H3O+ concentration. From there you put that i...

Gerald Bernal1I

Buffers are solutions that when an acid or a base is added to the solution, it does not affect the pH. Buffers are usually made by adding a weak acid with its salt in water.

Gerald Bernal1I

you divide the change number by the concentration of the acid. Then you multiply by 100 if you want the percent.

Gerald Bernal1I

Why does temperature change the K value, does it have to do with changing reaction rate?

Gerald Bernal1I

With any change the equilibrium will shift a certain way. A general rule is if there is more of reactant, the equilibrium will shift to the right (product) since it has more reactants to form product, and the same goes for an increase of product concentration: it will shift left to create the reacta...

Gerald Bernal1I

Since it is a constant, concentration of the product or reactant changing like for example adding more reactant or product will not change Kc, instead the system will shift accordingly to reach equilibrium again and that will happen when the system reaches the Kc ratio. The only thing that can affec...

Gerald Bernal1I

Solids and liquids are not added because their concentration does not affect the concentration of the reactants and therefore assumed to have a concentration of 1. Because of this, the 1 of their concentration is omitted from the equilibrium constant equation.

Gerald Bernal1I

The inert gas does not change the volume and therefore does not change the concentrations of the gases therefore it will not affect the equilibrium.

Gerald Bernal1I

His principle states a change in pressure, temperature, or concentration of a reactant when applied to a system, the system will counteract the change and shift accordingly in order to return back to equilibrium.

Gerald Bernal1I

For now we should just know the ideal gas law equation and that gases are compressible.

Gerald Bernal1I

When asked to write the ms of a certain configuration you just have to pick one of them since each refers to one electron spinning one way. Since there is no definite way to know you can pick one, +1/2 being up spin and -1/2 being down spin.

Gerald Bernal1I

For finding charges in metals you have to know some fixed oxidation states and rules like H2O being a neutral molecule with a charge of 0 and OH always has a -1 charge.

Gerald Bernal1I

It is one of the only metal ions that is able to bond with CH3 which is a biological molecule necessary in our system for many functions.

Gerald Bernal1I

The lewis acid and base definition is used more for salts and compounds that do not have H ions or do not fit the definition of a bronsted acid or base. For a majority of acids and bases, the bronsted acid definition is used unless otherwise noted.

Gerald Bernal1I

Since Cl is more electronegative it will be able to ionize more easily since the bond is weaker. When it comes to acids and bases the ability to ionize is what matters since that is what will producing the pH or pOH.

Gerald Bernal1I

The strength of an acid is just based on their ability to ionize completely in water and therefore be able to produce H+ ions or OH- ions.

Gerald Bernal1I

There is no way to tell the spin of the electrons but in general you can use either +1/2 or -1/2. When they ask for quantum numbers you can use either or.

Gerald Bernal1I

This just refers to the Schrodinger equation which is what the orbitals are based off of. The equation basically explains why orbitals were used for interpretation.

Gerald Bernal1I

Another way to check if it was ionized was to use the ph value and from that plug it in to the Ka equation. pH just refers to the H+ concentration and therefore you would know the value of H+ and A- and would be able to solve for the HA value which ended up being larger than the other concentrations.

Gerald Bernal1I

Equilibrium sign is added only for weak acids and bases since they do not dissociate or ionize fully.

Gerald Bernal1I

It depends on the problem and what units the equation you are using uses. Sometimes it will give you a certain unit and the final question will ask you to convert it to a different unit.

Gerald Bernal1I

How would we know the oxidation number if the formula is just given? Certain ions have fixed oxidation states like oxygen is always (2-) and SO4 is always ((2-) and CN is always (-1) and so on. Molecules like H2O and gases like HOFBRINCl have an oxidation number of (0). https://d2jmvrsizmvf4x.cloud...

Gerald Bernal1I

Polydentates are just able to bind multiple molecules by having two or more lone pairs. A ligands ability to bind at multiple sites depends on its orbitals and number of electrons, therefore some ligands are only able to bind once and others are able to bind more. Chelating ligands bind cations tigh...

Gerald Bernal1I

It should be written out in order to specify the difference between the molecular structure. The molecule is the same therefore the only difference is the position of the molecules and the cis and trans prefixes specify which position you are referring to.

Gerald Bernal1I

When a metal oxide reacts with water, a base is produced and OH- ions are also produced. Nonmetal oxides produce acids.
https://qph.fs.quoracdn.net/main-qimg-c ... 06f3907d49

Gerald Bernal1I

The oxidation number should be written even when it is zero next to the metal because metals can have various oxidation states which is why it needs to be specified which oxidation state it is in.

Gerald Bernal1I

It's six because ethylene diamine I believe is considered two ligands therefore two of these would make it four and then plus the 2 Cl, it would give a coordination number of 6.

Gerald Bernal1I

Yes, it is due to the properties of the ring structure. The atoms are closer together therefore making the bond tighter with their electron density.

Gerald Bernal1I

Sigma bonds overlap and can rotate while pi bonds are directly next to each other and are not able to rotate.

Gerald Bernal1I

Bronsteds says that acids are H atom donors and lewis acids are electron donors. Bronsted's definition limits acids only to compounds that have hydrogen atoms bonded to it while Lewis acids definition can be expanded to any ionic compound that has an atom donating an electron.

Gerald Bernal1I

Lavelle said to use the one that has the asterisk next to it but he also said in his email that either or is fine.

Gerald Bernal1I

It depends on which definition of acid we are using since a Lewis acid is any compound that is an electron donor and Bronsted's definition is any compound that donates a hydrogen atom in water. For the most part, all acids should have a hydrogen bonded to them.

Gerald Bernal1I

It's just a difference in name. Cyano is the one you should use since it is the one Lavelle has asterisked on his website, but he said either or is fine. Cyanido is just the new IUPAC Name convention.

Gerald Bernal1I

The bond angles are just experimental observations, so some of the angles just have to be memorized. Lavelle said that we just have to know when to assume a bond angle will be less than another if it has more lone pairs, etc.

Gerald Bernal1I

You look for which atoms are electronegative and see where they are placed in order to see if their dipoles cancel out or make the molecule polar.

Gerald Bernal1I

I don't think you have to memorize the melting points, but just know the strength of each molecular interaction and compare them.

Gerald Bernal1I

They are treated the same because they are all just an area of electron density no matter the bonds.

Gerald Bernal1I

The lewis structures are only showing the valence electrons which with the octet rule means 8 electrons in order for the atom to be stable. Expanding the octet with atoms that are able to just depends on the formal charge of the atoms and what would ultimately lead to a stable structure.

Gerald Bernal1I

Shorter bond lengths are stronger because there are more electrons to break and the electron density is higher.

Gerald Bernal1I

Electronegativity describes the tendency of an atom to attract a shared pair of electrons towards itself. Bond strength increases as the difference in electronegativity between the atoms that are bonded increases.

Gerald Bernal1I

I believe for anything to do with electrons and electron emission I think he wants us to use this one En = - h R/n^2 . This is what is on the constants and equations sheet.

Gerald Bernal1I

It wouldn't bind with phosphorus because it would cause the formal charge to change to one that is energetically unfavorable. If the hydrogen was bonded to the phosphorus it would change to a formal charge of -1 rather than 0 which is what it has with 5 shared electron bonds. Additionally the hydrog...

Gerald Bernal1I

You only use the light equation or any equations dealing with c which is speed of light when it has anything to do with EM radiation because the speed of light is a form of EM radiation which would have the same units as other energy from EM radiation. This is why DeBroglie is a separate equation be...

Gerald Bernal1I

The x indicates which plane the 2p orbital is in. The two orbitals can lie on the x, y, or z plane. https://qph.fs.quoracdn.net/main-qimg-5 ... 63712171dd

Gerald Bernal1I

An electron in the 2px state just means its in the p orbital. The p orbital has three possible areas two electrons (2px,2py,2pz) so the x is just there to denote that its in the first p orbital.

Gerald Bernal1I

Could someone explain how we are able to get 2,1,0,-1,-2 when we are finding the magnetic quantum numbers(ml) for the d orbitals. I know it goes l, l-1,..-l but how do we get -1 from this pattern? I am thinking 2,1,0(l-2), but would we get -1 from l-3 or something else? Could someone explain the pat...

Gerald Bernal1I

I'm also having trouble with this problem. I found v using the equation v=c/λ and then used that in the equation ΔE= hv. However, from there I got a little lost. I used the equation En= -hR/ n^2 using n=1 to find Ei. I then plugged in ΔE and Ei into ΔE= Ef-EI to get Ef which I set equal to En= -hR/...

Gerald Bernal1I

The symbol he used here is rho so I don't think he was talking about orbitals here.

Gerald Bernal1I

In the last few slides of lecture, Dr. Lavelle used this equation $\psi ^2=e^-*\rho Distribution$
Does anyone know what the rho symbol stands for in this equation or what its value is?

Gerald Bernal1I

It should be photoelectric effect since it showed that light has discrete amount of energies called photons. It showed that no matter how the amplitude changed, the energy was still the same, but when the frequency was changed, the wavelength, it was able to displace electrons.

Gerald Bernal1I

I believe the only one that doesn't apply to EM radiation is the De Broglie equation. The others deal with light therefore they are EM radiation equations.

Gerald Bernal1I

It works for any particle (object that has rest mass) with momentum. It is used for objects such as cars or baseballs as shown in the lecture which do not have detectable wavelengths. De Broglie claimed that all particles must have wave like properties.

Gerald Bernal1I

The experiment that was shown in class and in the book where there were two cut outs where light was shined through and the light appeared where there was a wall in front. If light behaved like a particle it would shine through the cutout and appear right there, but it did not which meant that waves...

Gerald Bernal1I

I believe the light emitted is just the difference between the frequency that displaced the atom and the threshold energy, so I don't know if its a higher frequency each time since sometimes it can be zero when it matches the threshold energy.

Gerald Bernal1I

The photoelectric effect (i.e. shining light on a metal and finding the threshold energy of an electron) was used as strong evidence that light is a photon with certain energy/frequency. This proved that electromagnetic radiation including electrons behaved in a particle like matter rather than a wa...

Gerald Bernal1I

If that were to happen then yes, the electron would exhibit particle like properties rather than wave like since 10^-15 is the cut off.

Gerald Bernal1I

I also had trouble with this one. First you would convert the 5 g to moles and then divide by the 150 ml to get the concentration. Since you are extracting from an already dissolved solution the new volume is the 20 ml. So, when you are doing M initial x V initial = M final x V final, you would use ...

Gerald Bernal1I

If it doesn't specify, I would just go with what the problem is using. I would just go with the pm for measurement of length.

Gerald Bernal1I

The problem wants you to write the chemical equation out yourself rather than provide it. This is a combustion reaction since butane is being burned, therefore for any combustion reaction the gas would react with O2 and produce CO2 and H2O. For this problem the equation would be 4C4H10 + O2 --> CO2 ...

Gerald Bernal1I

What do you mean atom ratio?

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