CHEMISTRY COMMUNITY

Jessica Tran_3K

Ionization energy is the amount of energy required to remove an electron from an atom, while electronegativity is the amount of energy required to add an electron!

Jessica Tran_3K

The negative charge should usually be placed on the most electronegative atom (typically oxygen)!

Jessica Tran_3K

yes! also, lone pairs on N, O, or F serve as hydrogen bonding sites.

Jessica Tran_3K

IMFs take precedence over bond length when considering melting/boiling points of molecules!

Jessica Tran_3K

I will be reviewing key concepts, going over lecture notes, watching videos, practicing problems/reading the textbook, and attending review sessions!

Jessica Tran_3K

I think knowing the 7 common acids would be helpful! They are:
hydrochloric acid. HCL.
hydrobromic acid. HBr.
Hydroiodic acid. HI.
Nitric acid. HNO3.
Perchloric acid. HClO4.
Sulfuric acid. H2SO4.
Chloric acid. HClO3

Jessica Tran_3K

Jessica Tran_3K

I would also start out by drawing the molecule and determining whether it is polar or nonpolar. From there, you can tell if the molecule has LDFs and Dipole Dipole IMFs if the molecule is polar or LDFs only if it's nonpolar.

Jessica Tran_3K

I think that's all we should know

Jessica Tran_3K

A ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves donation of one or more of the ligand's electron pairs.

Jessica Tran_3K

Bent and angular are the same and can be used interchangeably! It's all up to personal preference whether to call the shape bent or angular. 2 bonded and 1 lone pair is bent, and 2 bonded and 2 lone pairs is also bent.

Jessica Tran_3K

If the question asks for shape, I believe that you would write down the molecular geometry.

Jessica Tran_3K

If there is an ionic bond between a positively charged cation and a negatively charged anion, then ion-ion interactions are present.

Jessica Tran_3K

We should also be able to use strengths of IMFs to explain the difference in boiling points, melting points, and vapor pressure between molecules too

Jessica Tran_3K

Hi,

There are videos on Youtube you could look up that focus on molecular geometry and have some practice problems. Hope that helps!

Jessica Tran_3K

Another way to determine polarity that might be helpful would be to imagine strings on the ends of the atom. If you pull on the strings and there's a stronger pull on one end of the molecule compared to the other, then the molecule is polar. The same goes vice versa (equal pull all around = nonpolar...

Jessica Tran_3K

Also, additional lone pairs force bonding electrons closer together.

Jessica Tran_3K

Test 2 will be next week in our discussion section! It'll also be our last discussion before finals if you have it on Thurs/Fri due to Thanksgiving break.

Jessica Tran_3K

How are you guys studying for test 2?

Jessica Tran_3K

Hi,

I think test 2 will cover the VSEPR model, shapes, polar/nonpolar, and strengths of repulsion.

Jessica Tran_3K

I also agree ^^ I think as long as the concept is still relevant, it should be fine.

Jessica Tran_3K

How do we know when a molecule has resonance?

Jessica Tran_3K

yes, and it is also the same conversion for km, kg, and kj (anything that has kilo in it).

Jessica Tran_3K

Test 2 should be in the week of Nov 18-22 (about two weeks from now) in your discussion section.

Jessica Tran_3K

Ionization does have the same trend; it increases going across the periodic table and decreases going down.

Jessica Tran_3K

Also, just something extra is that single bonds have only 1 sigma bond, while double bonds have 1 sigma bond and 1 pi bond!

Jessica Tran_3K

How often are we supposed to use formal charge to check our lewis structures? Do you check it every time?

Jessica Tran_3K

Also, how do we check our GPA? Is it also under exam and homework grades or would it be on our DARS?

Jessica Tran_3K

I also think this is the best way to go about it. I usually do trial and error, and as I get used to drawing lewis structures, I can kind of predict/tell how to draw the structures/remember what it's supposed to look like if I've drawn it before.

Jessica Tran_3K

I agree ^^ I believe that there might be 1 question on the fundamentals at most since we had a test on it already

Jessica Tran_3K

I would use dots at first, but then switch over to lines once I consistently remember that a line represents shared electrons since it looks cleaner when drawing lewis structures!

Jessica Tran_3K

How do you calculate formal charges? I know the formula, but I don't really understand how to apply it. Thank you!

Jessica Tran_3K

The number of valence electrons is the group number, which you can count from left to right on the periodic table.

Jessica Tran_3K

When drawing lewis structures, how do you know when to draw the double bond? and between which elements?

Jessica Tran_3K

Hi!

I think most of the time, we would use the short hand configuration with the noble gases unless the question states to write out the entire thing.

Jessica Tran_3K

When electrons are paired, that means they are in the same orbital and have opposite spin. When they are parallel, that means one electron is in each different orbital and they have the same spin.

Jessica Tran_3K

I think it was mentioned in lecture that we wouldn't be able to determine which magnetic quantum numbers (-1, 0, 1) are for px, py, pz since it's depends on how the axis is drawn (subjective/varies by person).

Jessica Tran_3K

I would review all my notes first and then attempt to do practice problems from each section! Taking note of which sections I found difficult, I'd watch videos for those sections on Youtube and on prof. Lavelle's website and then reattempt the questions I missed.

Jessica Tran_3K

Increasing the energy of the light (more photons) would increase the amount of electrons ejected. Also, increasing intensity of the light would not increase amount of ejected electrons.

Jessica Tran_3K

Hi!
Inner electrons shield outer electrons from electrostatic attraction of the positive nucleus, so outer electrons feel a reduced electrostatic attraction which results in an effective nuclear charge. Also, outer electrons determine the bonds that the atom makes.

Jessica Tran_3K

I personally watch videos on Youtube whenever I don't understand a topic or need a quick refresher on the fundamentals (Khan Academy, Professor Dave Explains, and Bozeman Science are my favorites!). Aside from that, I find that solving many textbook problems with a study buddy and going back to re-s...

Jessica Tran_3K

Hi guys,

I'm a little confused about some of the variables in the equations that we recently learned. How do you guys differentiate when the "V" in the equation denotes frequency versus velocity?

Jessica Tran_3K

It's Planck's constant (6.626x10^-34 Jxs)!

Jessica Tran_3K

Frequency and wavelength are inversely related to each other; the greater the frequency, the shorter the wavelength and vice versa. Frequency is denoted by the v with the curve at the end and wavelength is denoted by lambda.

Jessica Tran_3K

Hi,

If we are asked to perform calculations (ie calculate mass % composition or molar mass) in a problem that doesn't give us numbers to work with, how would we know how many sig figs to include in our answer? What's a good rule of thumb to go by in this case?

Thanks!

Jessica Tran_3K

Hi,

I don't think you can have more than one limiting reactant. Once the limiting reactant is used up, the reaction can no longer continue.

Jessica Tran_3K

Hi,

g.mol-1 is grams per mol, so it is not interchangeable with the unit mol. I am not quite sure about g.mol either.

Jessica Tran_3K

Hello! First, we need to convert the given grams to mols (CH4 would be 0.0022 mols, H2O would be 0.0060 mols). If we converted both CH4 and H20 to mols of CO using the mol ratio, we can determine that CH4 is the limiting reactant since it produces less of the product CO. Now we can use the amount of...

Jessica Tran_3K

I think both would require the same exact amount because of how there's 1 mole CuSO4 in the compound. Although they aren't the same, they both would contain the same amount of CuSO4, hence why "the amount of CuSO4(5H2O) you need to supply is the same as the amount of CuSO4 needed to prepare the...

Jessica Tran_3K

Hi! Yes, Mg is the limiting reactant. Now that you've concluded that, you can use dimensional analysis to convert the amount of mols you calculated for Mg into Boron using the mole ratio (2 mols of B for 3 mols of Mg) and then the molar mass to convert mols to grams (for the mass of Boron).

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