CHEMISTRY COMMUNITY

Natalie Wang 1B

Aqueous molecules disassociate in water. Also, you should only use the concentrations of aqueous compounds when calculating the Ka or Kb.

Natalie Wang 1B

It's a good rule of thumb to know that elements near the metalloids will form amphoteric salts. For example, aluminum oxide will form an amphoteric salt.

Natalie Wang 1B

Cis platinum chelates a nitrogenous base and blocks DNA replication.

Natalie Wang 1B

Another way to think about it is that in the pH of 2, there are a lot of H+ ions. In equilibrium reactions, which is what happens when weak acids disassociate, an equilibrium must be maintained. Since there are a lot of H+ ions, this would cause the reaction to favor the opposite end of the acid dis...

Natalie Wang 1B

In 6.21 c, it asks to mark the amphiprotic areas of Thymine. According to the solutions manual, the Nitrogen atoms are amphiprotic. Why is that? Can someone explain this to me?

Natalie Wang 1B

As everyone else has said, Aluminum can have less than the octet rule. Boron is another important element that can have less than the octet rule.

Natalie Wang 1B

Yes, the AXE formula is part of VSEPR Theory, which is used to determine a molecule's shape. Just remember that you can't use hybridization to determine a molecule's shape!

Natalie Wang 1B

For CH20, carbon will have a sp2 hybridization because it has a single bond for each H atom and a double bond with the O atom. Carbon will only have 3 electron densities, which correlates with sp2.

Natalie Wang 1B

I agree. I believe that s character is referring to the role of the s orbital in the hybridization. An sp2 hybridized orbital would have more s character than an sp3 hybridized orbital. And, as we know from molecular structures, a structure with sp3 hybridized orbitals (like a tetrahedral molecule) ...

Natalie Wang 1B

The answer would be b. The two NH2 molecules are close to each other, so a metal atom can be drawn between them, forming a bidentate ligand, which would be a chelate. Here is an image address to what I mean: https://ars.els-cdn.com/content/image/3 ... 186880.jpg

Natalie Wang 1B

Molecules have hybridizations to form enough bonds. For example, CH4 has hybridization because normally C only has 2 unpaired electrons. With an sp3 hybrdization, C has 4 unpaired electrons that can bond with 4 H's. On the other hand, hybridization can also ensure the stability of a molecule. For ex...

Natalie Wang 1B

I asked my TA, and he said that the angles will be less than 120 and 90.

Natalie Wang 1B

I was really confused about this too, but I highly recommend that you watch this Youtube video to contextualize the answer: https://www.youtube.com/watch?v=As-hcYY8Yaw Start at the the 5 minute mark. To give you a written answer, CH2Cl2 is polar because of the bond angles. Remember that a tetrahedra...

Natalie Wang 1B

For the first part of the question, think about symmetry. If the two chlorine bonds are right across from each other, their dipole moments will cancel each other out. Therefore, Form 3 is nonpolar. Form 1 and Form 2 don't have the chlorine atoms straight across each other, so their dipole moments do...

Natalie Wang 1B

I'm not sure why the answer is like that. But there is no way that Boron could have a lone pair. The hybridization should just be sp3.

Natalie Wang 1B

I don't think sigma and pi bonds really affect VSEPR. VSEPR involves where regions where there are valence electrons. If there are only 2 areas where valence electrons can be found, the molecule is linear. If there are only 3 areas where valence electrons can be found, the molecule is trigonal plana...

Natalie Wang 1B

Dispersion forces are stronger for bigger molecules. Therefore, a molecule with atoms of bigger atomic radii will have stronger dispersion forces.

Natalie Wang 1B

I think you are right. Ion-dipole has a larger difference in charges than H bonding.

Natalie Wang 1B

If the molecule is asymmetrical, it will be polar. Therefore, for example, CHCl3 would be polar because the H makes it asymmetrical.

Natalie Wang 1B

If the solid has strong intermolecular forces, the lattice energy will increase. The lattice energy is basically the amount of energy requires to break those connections between molecules. As a result, strong intermolecular forces increase lattice energy.

Natalie Wang 1B

Se is in the middle of two OH groups and two double bonded O atoms. Each bond has dipole moment since there is a substantial difference in electronegativity between Se and each O it is bonded to. If you are wondering why H2SeO4 might be a polar molecule, I saw a post that has a similar topic to that...

Natalie Wang 1B

The bigger a hydrocarbon, the stronger the intermolecular bonds are. In dispersion forces, more electrons means larger dispersion forces. That explains why bigger molecules have stronger dispersion forces.

Natalie Wang 1B

Dipole-dipole interactions occur between polar molecules. For the answer, choose the molecules that have an overall polarity. The asymmetrical molecules will be polar.

Natalie Wang 1B

When there are more electrons, London (Dipole-dipole/Dispersion) Forces are stronger. CCl4 has more electrons than CH4, so it has stronger intermolecular forces.

Natalie Wang 1B

To simplify radicals, just look at the total valence electrons of the molecule. If the total is even, the molecule is not radical. If the total is odd, the molecule is radical.

Natalie Wang 1B

The central atom is usually the atom with the least ionization energy. Of course if the molecule has hydrogen, hydrogen can't be the central atom. For the Lewis Structure, it is important for the central atom to have 0 formal charge.

Natalie Wang 1B

For most molecules, the atom that gets the extra electron is the one that that already has other lone pairs. Of course, for problem 5a from Focus 2C, there is a molecule that is ClO. The extra electron is put onto Cl. I think it is likely because Cl is more electronegative. But also, it makes Cl's f...

Natalie Wang 1B

Usually lone pairs are used to satisfy the total amount of valence electrons in the molecule. Otherwise, if you are dealing with a molecule with an atom from period 3 (or beyond) as the central atom (atoms that are exceptions to the octet rule), having lone pairs might bring their formal charges to ...

Natalie Wang 1B

The difference is their electronegativity. If the electronegativity between the two atoms is more than 2.5, the bond is ionic. If the electronegativity between the two atoms is less than 1.5, the bond is covalent. Between 1.5 and 2.5, the bond has ionic and covalent components.

Natalie Wang 1B

Actually, Aluminum usually donates its valence electrons to have an octet (Al+3).

Natalie Wang 1B

Having a 0 formal charge is the most stable, so the Sulfur has a 0 formal charge. Of course, this causes two of the oxygen atoms bonded to sulfur to each have a formal charge of -1. This is fine because oxygen is already more electronegative than sulfur, so it attracts the electrons more. Even thoug...

Natalie Wang 1B

Some exceptions to remember:
1. H, He, Li, and Be are exceptions to the Octet rule. That means they don't need 8 valence electrons.
2. P, S, and Cl can have more than 8 valence electrons. For example, in phosphorous pentachloride, phosphorous has 10 electrons.

Natalie Wang 1B

Also, double bonds are stronger than single bonds, so they require more energy to break.

Natalie Wang 1B

This rule applies to all bonds between all atoms. Generally, single bonds are longer than double bonds.

Natalie Wang 1B

Hi everybody, I made a groupme if anyone is interested! I'll probably post it on facebook, too.
https://app.groupme.com/join_group/55046813/XcQgQkkM

Natalie Wang 1B

I like to think Hund's Rule as a school bus. When you enter a bus, you would rather take the empty seat than sit next to someone else. This can apply to electrons in each subshell of an orbital. The subshells need to each have 1 electron before there can be two electron in each subshell.

Natalie Wang 1B

Actually, I saw on a recent post that if it is + - n, the uncertainty is 2n. Therefore, the uncertainty of this should be 10 mm, I think.

Natalie Wang 1B

Yes! The uncertainty of momentum and the uncertainty of position are indirectly proportional. If you change the equation, you will see that:
p >= h/(4pi *x)
You can see that p is proportional to 1/x. So if p goes up, then x needs to go down and vice versa.

Natalie Wang 1B

The Hamiltonian is the double derivative or the wave function (psi). The double derivative of the wave function is the same as the energy of the electron.

Natalie Wang 1B

Schrodinger's equation is used to describes the probable positions of an electron in an atom. The equation involved sin and cos, so the graph is in waves. This connects to how electrons have wavelike properties.

Natalie Wang 1B

I'm not exactly sure what resonance of momentum is. However, (fun fact) there is this process called surface plasmon resonance for metal. Basically, when light hits a metal, like gold, the atoms' electron clouds absorb the light and begin moving around. Then, these electron clouds reflect leftover l...

Natalie Wang 1B

The circular standing wave model shows possible wave movements of an electron around the nucleus. The model shows multiple waves to show that electrons oscillate and have wavelike properties.

Natalie Wang 1B

At the moment, I'm distinguishing them based off of electromagnetic radiation and the quantum mechanics of electrons. For example, De Brogile's equation can only be applied to electrons, NOT light.

Natalie Wang 1B

When waves hit something, they bend. This process if called diffraction. For example, if light is shone through a small slit, the waves bend as they interact with each other through that tiny opening. When electrons pass through a crystal, their movement patterns are similar to the patterns of diffr...

Natalie Wang 1B

It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to: These two equations are applied to light in the theory that light is a wave: c = λv = 3*10^8 (speed of light = wavelength ...

Natalie Wang 1B

It's important to distinguish between equations that are relevant to light (EM radiation) and quantum movement of electrons. For light specifically, you should pay attention to: These two equations are applied to light in the theory that light is a wave: c = λv = 3*10^8 (speed of light = wavelength ...

Natalie Wang 1B

Also, a really handy trick with empirical and molecular formulas, is that if you're looking for the molecular formula of a compound, and you know the compound's molar mass (along with the empirical formula's molar mass), you can divide the compound's molar mass by the empirical formula's molar mass....

Natalie Wang 1B

To find molarity, you have to divide the mols of solute by the volume of the solution. Convert KCL to mols. Then, convert the 125 mL to L. Finally, divide the mols of KCL by the volume in L to get the answer.

Natalie Wang 1B

Sodium Carbonate has two sodium ions, so the ratio needs to be taken into account. When the problem asks you to find the volume for 2.15 mM of Na+, you need to convert 2.15 mM of Na+ into the amount of moles for sodium carbonate. To do that, you would need to show how 1 mol of sodium carbonate has 2...

Natalie Wang 1B

I don't know if anyone has done this yet, but I would really like to start a study group! We can reserve study rooms in some of the halls on the hill. Reply if you're interested!

Natalie Wang 1B

I actually asked my TA, and he said that for now, we don't need to know how to write chemical formulas correctly. We also don't need to know how to write out chemical formulas from just the compound's name for our first test! Apparently, we'll be learning the basics of chemical formulas and nomencla...

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