CHEMISTRY COMMUNITY

Nina Tartibi 1F

pKa measures the strength of an acid. The lower the value of pKa, the stronger the acid. The equation is the negative log of the Ka value, which is the degree of protonation/iodization in water. You can also use pKb and Kb to measure the strength of bases as well.

Nina Tartibi 1F

Hi!! Yes I was pretty confused on distinguishing the two of them until literally a couple hours ago when I went to the review session, but basically a Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor. A Bronsted acid is a Hydrogen proton donor, and a Bronsted base ...

Nina Tartibi 1F

HF is not a strong acid because when dealing with hydrohalic acids, you distinguish the strength by atomic radius. F is one of the smallest atoms on the periodic table, and it's the smallest out of the halogens, so therefore it isn't a strong acid, and acids such as HCl, HBr, and HI are all stronger...

Nina Tartibi 1F

I'm pretty sure that if an acid/base is strong, the conjugate must be weak. Conjugate acid-base pairs have a conjugate see-saw, which is the rule that the stronger the acid, the weaker its conjugate base, and vice versa. Acid strength is defined by depronation, and the conjugate base is what you mak...

Nina Tartibi 1F

We will be able to have a calculator on the final. In order to determine the pH of a solution, we have to calculate the -log(Molarity of solution), which would require a calculator. If they give the pH and ask for pOH, however, you can just subtract 14-pH=pOH, which doesn't require a calculator.

Nina Tartibi 1F

Like Simona said, I also like to think of the geometrical 3D shapes of the molecules, because for example, by looking at a linear molecule, you could see that the atoms are all on the same plane (co-planar), but a molecule that is trigonal pyramidal would not have atoms on the same plane, for if you...

Nina Tartibi 1F

I don't believe that resonance structures would rotate, because there is still a delocalized electron that makes the double bond in resonance structures. Therefore, with that pi-bond in the double bond, it would restrict the molecule from rotating.

Nina Tartibi 1F

Cobalt is the transition metal in Vitamin B-12! I think we need to know it because of its biological importance and our necessity for it, but also because it's a common and well-known coordination complex.

Nina Tartibi 1F

yes you look at the number of bonds and lone pairs around the transition metal

Nina Tartibi 1F

I believe that you have to memorize table 9C.1 in the textbook (polyatomic ions and their charges) and the ligand names as well

Nina Tartibi 1F

You can identify a chelate if the structure of the molecule has more than one lone pair on the atoms in the structure. If it only has one lone pair, it is a monodentate.

Nina Tartibi 1F

Correct me if I'm wrong, but I believe delocalized bonds are when the electrons can move around to different bonds, similar to resonance. So does this mean that resonant structures have delocalized bonds?

Nina Tartibi 1F

Leyla Anwar 1C wrote:Are ligands specific to transition metals/metals or can they be applied to all elements?

I believe ligands are only specific to metals because when I looked it up, the definition of a ligand is an ion/molecule that binds to a central metal atom to form a coordination complex.

Nina Tartibi 1F

Natallie K 3B wrote:Electrons are delocalized whenever there is a resonance structure, not just a ring such as benzene.

This might be redundant but, when electrons are delocalized does it just mean that the structure has resonance or is there more to it than that? I was also a bit confused on this

Nina Tartibi 1F

Equatorial atoms are on the horizontal x-axis, while axial atoms are on the vertical y-axis

Nina Tartibi 1F

The more electronegativity difference a molecule has, the more soluble it is. To answer your question about NaF vs. NaI, Fluorine is the most electronegative element on the periodic table, and Iodine, although very electronegative, is not as strong as F, because it's below F on the table (electroneg...

Nina Tartibi 1F

Chem_Mod wrote:Ionic bonds > Hydrogen bonding > Dipole-dipole interactions > London dispersion forces

To add onto that, it's ion-ion>ion-dipole (just to be more specific about the ionic bonds)

Nina Tartibi 1F

Another question that I am confused about is how LDFs are affected by the molecule's surface area? If I am not mistaken, I believe that greater surface area means strong LDFs but why would that be the case? The greater the surface area of a molecule, the stronger LDF it has, because the valence ele...

Nina Tartibi 1F

aashmi_agrawal_3j wrote:A dipole is basically where there is a partial positive or negative because electrons are shared unequally.

So technically, could you say that a dipole is just a covalent bond with ionic character? Since structures with unequally shared electrons are considered polar.

Nina Tartibi 1F

Hydrogen bonding is only achieved when an H atom bonds with either N,O, or F. When looking at two Lewis structures, to determine if they can have hydrogen bonding, a Hydrogen has to bond with N,O,F, OR H itself IF that H is bonded to an N,O, or F atom.

Nina Tartibi 1F

Hydrogen bonds are the strongest bond because N,O, and F are the most electronegative elements on the periodic table, and H is one of the least, so there is a large difference in electronegativity, which causes the strongest dipole moment --> strongest IMF

Nina Tartibi 1F

A dipole moment in a molecule occurs when electrons are unequally shared between atoms. It can technically occur between all atoms in a molecule regardless of polarity. So no it does not determine if a molecule is polar or nonpolar. Wait but doesn't polarity mean exactly that? An unequal sharing of...

Nina Tartibi 1F

You would start with octet rule so all the atoms in the molecule are stable, and then you would calculate formal charge, hopefully getting zero as the total FC.

Nina Tartibi 1F

When we say that electrons are delocalized, we mean that the electrons for a multiple bond in a resonance structure are equally likely to be anywhere on the resonance structure. The delocalized electrons are not associated with a particular atom or covalent bond. If they were, then you would have s...

Nina Tartibi 1F

I also have a question about drawing lewis structures on the midterm. I noticed that sometimes the textbook writes the molecular formula in the order it wants us to draw the lewis structure, even if this order doesn't minimize formal charge. Like ClNO2 would be drawn with Cl attached to N, and then...

Nina Tartibi 1F

The trend of electronegativity on the periodic table is up and to the right, therefore F is the most electronegative element. I think we just have to know the trend of electronegativity, and we would be given the chart with electronegativity if we were to be asked a question regarding that

Nina Tartibi 1F

Noble gases are stable and have already reached full octet (full valence shell). Therefore, Neon gas, being a noble gas, is not included in electronegativity (or electron affinity and atomic radius for that matter).

Nina Tartibi 1F

Hello! Resonance is a type of Lewis structure that basically means it's the same arrangement of atoms but different arrangements of electron placement. So for example, nitrate ion (NO3-)'s Lewis structure has resonance because there is a double bond between one of the O atoms and the central N atom....

Nina Tartibi 1F

Yes! Polar covalent bonds resemble the same characteristics as ionic bonds, because there is an unequal distribution of electrons between the two elements. As stated in Lavelle's lecture #16, all covalent bonds have some ionic character, except when you are dealing with a bond between two of the sam...

Nina Tartibi 1F

I'm honestly not too sure about this question, but I think that might be impossible? Because noble gases have already reached octet and therefore are stable. However if this is possible I would like to know as well! Super interesting

Nina Tartibi 1F

Dr. Lavelle addressed this in the lecture and he stated that this is a rough guideline, therefore I don't believe we have to worry about what happens when there's an Electronegativity difference between 2 and 1.5.

Nina Tartibi 1F

Yes, I believe Lewis structures can portray both covalent and ionic bonds. What I did in chemistry in high school was indicate the electron transfer between a metal and a non-metal (ionic bond) using arrows, however Dr. Lavelle demonstrated not using arrows in his lecture so either way works.

Nina Tartibi 1F

The periodic trend for ionization energy is that it increases up a column and across a row, therefore Oxygen has a lower first ionization energy than Nitrogen and Fluorine because they are both to the right of Oxygen on the periodic table.

Nina Tartibi 1F

Boron only has 3 bonds, therefore it is one of the exceptions to the octet rule. It can only form three bonds.

Nina Tartibi 1F

The trends for ionization energy and electronegativity are the same: they increase in electronegativity/ionization energy as you go across a row and up a column. Flourine is the most electronegative element.

Nina Tartibi 1F

H, He, Li, and Be are the elements that don't follow the octet rule! All others should have 8 valence electrons.

Nina Tartibi 1F

You would multiply by 2 because since it is plus OR minus 1, the total change is 2, so you cover the whole uncertainty.

Nina Tartibi 1F

Since photons have no mass, the speed of light equation can be used to find wavelength of photons. However, when dealing with objects such as cars, baseballs, or electrons that involve mass, you'd use DeBroglie's equation. The wavelength of small objects are detectable such as electrons and neutrons...

Nina Tartibi 1F

Hey again! So when you solve using the equation (solving for the energy of the initial and the energy of the final state and subtracting it) that usually gives you a negative energy, which represent the CHANGE in energy of the ELECTRON after going from the initial state to the final state. Because t...

Nina Tartibi 1F

The way I remember is that the equation is V=R((1/n1^2)-(1/n2^2)) and just know that n1 is the lesser energy level, and n1 comes first. n1<n2

Nina Tartibi 1F

I believe we need to know the basic outline, for example 400-700nm is visible light and around 350nm is UV, x-rays are about 100nm to 1pm, 700-1000 is infrared and then greater is microwave. This will come in handy for Atomic Spectra because you would need to know that the Balmer series (visible lig...

Nina Tartibi 1F

This is a super interesting question. I'm pretty sure a black hole would be a form of black body radiation, since it absorbs all light. What I'm wondering is, we need to know conceptually what black body radiation is, but it's a theoretical. Someone in another post said that no such object exists, b...

Nina Tartibi 1F

Hi, here is a diagram Dr. Lavelle showed us in his lecture on Wednesday. This really helped me understand how the energy levels relate to the two different types of series. Is the gap between the Balmer and Lyman series where there are no detectable light lines the jump of energy between n=1 and n=...

Nina Tartibi 1F

I was also wondering whether a very large object (with a high mass) traveling at an extremely low speed could have a noticeable wavelength. However, I believe that since the velocity would have to be so low, the wave properties of that object are not really taken into account. This would be why a ca...

Nina Tartibi 1F

Hi! Planck's constant relates the energy carried by a single photon to its corresponding frequency. He found the constant using the kinetic energy of photoelectrons. Hope this helps!

Nina Tartibi 1F

So are wavelength and energy inversely proportional?

Nina Tartibi 1F

For #41 on the atomic spectra post-assessment, why does it say that the transition from n = 4 to n = 2 emits radiation of longer wavelength than the transition from n = 5 to n = 1. Isn't there more energy required to get from 5 to 1 than there is 4 to 2 because 5 is farther away to 1 than 4 is to 2?

Nina Tartibi 1F

16 should be fine (I have also been rounding when the molar mass is super close to the next nearest whole number), but if you take into account sig figs, the general rule is to take 4 decimal places of a molar mass.

Nina Tartibi 1F

Finding a mass percent makes it easier to find the empirical formula because since empirical formula is a ratio, you can just use 100g aka 100% as the setting point and scale the grams of each element in the compound to be out of 100g.

Nina Tartibi 1F

I believe it is 4 decimal places when dealing with chemical substances and problems.

Nina Tartibi 1F

I am pretty sure that is correct; the answer you provide is rounded to the number of decimal places you used in the equation itself. So, if you round the molar mass of an element to the thousandth place, the answer you get should also have been rounded to the thousandth place.

Nina Tartibi 1F

When dealing with balancing equations, you do not need to worry about having an equal number of stoichiometric coefficients on both sides of the equation. Balancing equations just means having an equal number of each substance on either side, therefore the mass is conserved.

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