CHEMISTRY COMMUNITY

Vanessa Chuang 4F

To my knowledge, there really isn't much of a difference in terms of accuracy with either form. I'm pretty sure we can use either form on the exam but most of the stuff we did in lecture is according to the old form.

Vanessa Chuang 4F

There's a few different naming conventions. The textbook uses one while Dr. Lavelle uses another. They technically are the same thing but just keep in mind that if you choose to use a particular convention, you should stick with the same one throughout naming the compound

Vanessa Chuang 4F

Basically a polydentate is a molecule (of sorts) that has multiple electron pair donating sites. This means that a polydentate can bind to multiple sites simultaneously. Each site does have to have at least one set of lone pairs to donate in order for the ligand to bind to the transition metal.

Vanessa Chuang 4F

The more ionic character something has, the more soluble it is. In order to determine the molecule with the greatest ionic character, you look for the molecule that has the greatest electronegativity difference between its cation and anion. For a, KCl has a greater difference; therefore, it is more ...

Vanessa Chuang 4F

Basically in order to determine the hybridization, you need to find how many regions of electron density there are. Once you figure that out by determining molecular shape, you match the corresponding hybridization to it. For example, for PCl4+, it has 4 regions of electron density (from its tetrahe...

Vanessa Chuang 4F

Shorter bonds means that the hydrogen is held more strongly to the central molecule so that when put into a solvent, there are less hydrogen atoms that are pulled off. Therefore, it is less acidic. Longer bonds mean that the hydrogen is held more weakly so that it is easier to pull it off when put i...

Vanessa Chuang 4F

To my knowledge, the only way to tell the difference between a strong acid and a weak acid is by memorizing the strong acids. I know that within the weak acids, there are ways to figure out which one is stronger of the weak acids but I'm pretty sure that between strong and weak acids you just have t...

Vanessa Chuang 4F

Hydrogen bonding sites are any place where hydrogen can potentially bond with an element. This includes both the actual hydrogen atom as well as the lone pairs on the F, O, and N atoms.

Vanessa Chuang 4F

The chemical formula for edta is C10H16N2O8

Vanessa Chuang 4F

The hybridization of the terminal atoms would be sp3 because it has one bonded pair of electrons and three lone pairs (which adds up to 4 regions of electron density).

Vanessa Chuang 4F

NaCl has a higher boiling point than HCl because it is ionic vs HCl which is not. Ion-ion bonds are always more strongly held together than non ion-ion bonds. That means you would need more energy to break apart NaCl than you would for HCl, which results in the higher boiling point of NaCl.

Vanessa Chuang 4F

NaCl has a higher melting point than HCl because it is ionic vs HCl which is not. Ion-ion bonds are always more strongly held together than non ion-ion bonds which means you need more energy to break apart NaCl. This results in a higher melting point.

Vanessa Chuang 4F

Hydrogen bonds cannot form between CO2 and H2O. The only forces that would occur between them are induced dipole-dipole forces because CO2 is nonpolar and H2O is polar. Hydrogen bonds can only form between a hydrogen attached to a F, O, or N atom and a F, O, or N atom that has a lone pair.

Vanessa Chuang 4F

For homework question 2E.13, we are asked to draw the shape of I3-. The resulting shape is an iodine as the central atom with 2 bonding pairs and 3 lone pairs. The answer to this is a linear shape. My question is do the 3 lone pairs on the central atom "cancel" each other out in order to m...

Vanessa Chuang 4F

It honestly depends on the transition metal. Part of it has to do with the oxidation number of the transition metal (ex: +1 vs +2), which then determines how many anions you have to use to cancel out this number.

Vanessa Chuang 4F

I'm not really sure you can find the dipole moment of a ground state. Dipole moments exist between elements in a molecule. I'm pretty sure a ground state does not consist of multiple elements that make up a molecule so it's not really possible to have a dipole moment. But if you were looking for the...

Vanessa Chuang 4F

The main reason why triple bonds are stronger is because the element shares more electrons. It's not necessarily that they have a stronger pull but more electrons are shared between the two of them. This means it will take more effort and energy to break the elements apart because there are more ele...

Vanessa Chuang 4F

Yes you are correct. The reason why an element can possibly have an extended octet (aka more than 8 electrons in the outer shell) is because there is the d orbital that the extra electrons can fill. This is the reason all elements located in rows 1 and 2 cannot possibly have more than 8 electrons be...

Vanessa Chuang 4F

Regardless of the fact that a formal charge might be zero, all elements in a compound have formal charges. As long as an element is sharing bonds with another element, it will have some variation of a formal charge. However, if you are asking about how you know which element should have a negative o...

Vanessa Chuang 4F

Yes, we can determine if covalent bonds are formed through the elements that make up that bond. Ionic bonds are when a non metal and a metal have a bond. Covalent bonds happen only between two non-metal elements. Within covalent bonds, there are also different types of covalent bonds as well.

Vanessa Chuang 4F

For the midterm we just took, there was no need to really know the difference. But in the future for the next test and the final, we will have to know the difference between poplar covalent and non polar covalent forces as well as the differences in their strengths, characteristics, etc.

Vanessa Chuang 4F

The Rydberg equation doesn't show different energy levels and how to conceptually get from one level to another one. Thus, it's easy to either get mixed up with emission vs absorption or to just completely forget to concepts behind the formula.

Vanessa Chuang 4F

Honestly it just is. SI units are really a construct - there isn't a particular purpose as to why kg was assigned as the SI foundation unit and not g.

Vanessa Chuang 4F

There wouldn't be a double bond between Cl and O because it would result in too many electrons used for the amount of valence electrons that actually exist (13 Ve-). We know the unpaired electron belongs to Cl because O can't have more than 8 valence electrons.

Vanessa Chuang 4F

The equation for electrostatic potential energy is Ue= kq1q2/r
Basically it's just saying that a charge will exert force on any other charge and thus potential energy will emerges because of that. K is a Coulomb's constant and r is the distance between charge 1 (q1) and charge 2 (q2)

Vanessa Chuang 4F

There are actually a fairly decent amount of exceptions to the octet rule. For example, the first 4 elements of the periodic table always have an incomplete octet because it is impossible for them to achieve the full octet. Elements period 3 and beyond have the capability to have an expanded octet b...

Vanessa Chuang 4F

Basically the longer the bond length, the weaker the bond strength is. Conversely, the shorter the bond length is, the stronger the bond strength. The closer two atoms are to one another, the more strongly bound they are, meaning it becomes harder to break apart the bond and vice versa.

Vanessa Chuang 4F

Yes, you are correct. In terms of the equation, the threshold energy would be represented by the work function. The work function technically refers to the energy the system needs to be put in whereas the threshold energy is what you defined it as. But honestly the two are basically the same thing f...

Vanessa Chuang 4F

For (a) Sb, the reason why it has 5 valence electrons is because it is in the Nitrogen group. It is 3 electrons from a noble gas (full shell), thus it already has 5 electrons. For (c) Mn, I counted the number of columns from the left. Since Mn is in the 7th column from the left, it has 7 valence ele...

Vanessa Chuang 4F

Yes, you are correct. Rhydberg is actually an expanded version that basically combines the Bohr frequency condition v=deltaE/h with En=-hR/n^2 for electrons of 2 different energy levels.

Vanessa Chuang 4F

How do you know the most likely charge for an ion to form? Are there any rules to follow regarding ion formation? For example for question 2A.15 d, the question asks what is the most likely charge for the ion of Ga is? I'm a little confused as to why the answer is +3.
Thank you!

Vanessa Chuang 4F

The orientation of x, y, and z are completely subjective and based on how you decide to view it. So in the context of when we are writing them, you just pick the way you want to assign them and stick with that assignment for the rest of the problem.

Vanessa Chuang 4F

The atomic radius actually decreases across a period because the number of protons increases. The increase in number of protons increases the nuclear charge (basically makes the positive charge in the nucleus more intense) and thus because of electrostatic attraction, the protons will pull in the el...

Vanessa Chuang 4F

Not sure if you made a typo or not, but the answer to 1E25c is (n-1)d^3ns^2. This is because the G5 transition metals are located in the 3rd section in the d block, making it d^3. And because it is to the right of G1 and G2, it also includes s^2. The principal quantum number n is an indicator of the...

Vanessa Chuang 4F

Much like the way the orbital fills in a specific order, electrons also remove in a particular way Because 3d has a higher energy, the electron will be removed from 4s first.

Vanessa Chuang 4F

You would fill the d subshell in so it would be 4d10s1. This is because the stability of a completely filled d subshell (or a half filled d5 shell) is better for the electrons to exist at, as opposed to 4d95s2

Vanessa Chuang 4F

You have to use E=hν and c = λ ν to get from energy to wavelength. Another way to write c = λ ν is ν=c/λ. If you substitute that into E=hν, you end up with E=hc/λ. If you reorder the variables, you can also get λ=hc/E.

Vanessa Chuang 4F

40: 7.46*10^-6 m 43: 1.22*10^-7 m 44: 9.73*10^-8 m; UV region To solve 40, you first need to use En = -h/ R n2 to find E6 and E5. Then in order to find the energy difference you subtract the initial energy from the final energy (E5-E6). You'll end up getting -2.66*10^-20 J. The question is asking fo...

Vanessa Chuang 4F

According to atomic spectra, electrons act more as a wave than as a particle. In order for a photon to excite an electron to the next energy level, the energy difference must match that of the one between two quantized energy levels. This energy is expressed as a wavelength, which is what allows us ...

Vanessa Chuang 4F

It would really depend on what the question has given you. For example, if the question gives you mass and velocity, then you will most likely use E=pv because none of the other equations need mass and velocity as an input. This would work similarly for other questions that give only certain values ...

Vanessa Chuang 4F

All Dr. Lavelle really said in class regarding black body radiation is that an object that absorbs all radiation at all wavelengths is called a black body. This means that since every and all wavelengths are absorbed, objects that are considered black bodies are basically invisible to the human eye.

Vanessa Chuang 4F

The question is asking you how to prepare the 0.5 M of NaOH. From the given information, you know you need 60.0 mL. So if you have 12 mL of 2.5 M solution already, you just need to add 48 mL of water to make the volume total 60 mL. So yes, it is just to have the same volume as the amount the questio...

Vanessa Chuang 4F

M.5 asks the following: "Solve this exercise without using a calculator. The reaction 6 ClO2(g) + 2 BrF3(l) --> 6 ClO2F(s) + Br2(l) is carried out with 12 mol ClO 2 and 5 mol BrF 3. (a) Identify the excess reactant. (b) Estimate how many moles of each product will be produced and how many moles...

Vanessa Chuang 4F

I think that electrons generally only drop one energy level at a time so they would emit one photon when they drop the first level and then emit a second photon when they drop the second level.
I'm not 100% sure about this though so if anyone knows for sure, please correct me if I'm wrong

Vanessa Chuang 4F

Unlike a lot of things we see in daily life (ex: a continuous stream of water), electrons only exist on specific energy levels (n=1, n=2, etc) and nothing else. This means that they can't be found anywhere in between these values. Being quantized means that the amount of energy absorbed or released ...

Vanessa Chuang 4F

Both of them deal with the absorption and emitting of photons. The photoelectric effect is when the electron absorbs enough energy to be completely ejected. Atomic spectra only wants to excite the electrons to observe them in an excited state, not remove them completely like the photoelectric effect...

Vanessa Chuang 4F

a) You can't just add elements to the product side if the reaction doesn't actually produce it (as stated in law of conservation of mass). In this case, O isn't actually produced from this equation so you wouldn't be allowed to just create it out of nowhere.
b) 2Cu +SO2-> 2CuO +S

Vanessa Chuang 4F

It depends on what the questions has given you and what it's asking for. The first one is generally used if you are trying to convert between moles and molarity given the volume. The second one is mostly used for dilution where you transfer different volumes from one concentration to another.

Vanessa Chuang 4F

When you solve for volume, you are dividing moles of Na over molarity of Na2CO3 (mol Na/molarity Na2CO3). However the question is asking you to solve for the volume of Na. Molarity is expressed as mol/L so the Na2CO3 molarity can also be written as mol/L Na2CO3. You would then convert the moles of N...

Vanessa Chuang 4F

Generally, if you're given a solid metal, it will stand by itself (ex: Mg, Cu, Ni, etc) unless the question states otherwise. However, for gases such as nitrogen and oxygen, those just happen to exist in the atmosphere as molecules (N2, O2, etc) which is why they need to be noted as so.

Vanessa Chuang 4F

In lecture I noticed that Dr. Lavelle usually determines the limiting reactant by comparing calculated moles to required moles. I was taught in high school to convert all moles to masses first and then do the comparison. In that case, does either method work? If not, then why is there a distinction?...

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