CHEMISTRY COMMUNITY

madeleinewright

Bond length is the most important factor when determining the strength of acids. Since the H-F bond is shorter and stronger than the H-Cl bond (because Cl is a larger atom than F), it will be more difficult to remove the hydrogen atom from HF, making it a weaker acid than HCl.

madeleinewright

To find the OH- concentration given the H+ concentration, you can use the equation 1.0x10^-14/[H+].

madeleinewright

Lewis bases are defined as atoms or molecules that can donate an electron lone pair. Since there is a lone pair on the nitrogen atom in NH3 that can be donated, it is a Lewis base.

madeleinewright

To get the pH from [H+], you take 10^-pH.

madeleinewright

Since pKa is the negative log of Ka, a smaller Ka would result in a larger pKa and a larger Ka would result in a smaller pKa.

madeleinewright

Formal charge doesn't really affect intermolecular forces, but it shows the stability in the structure of a molecule. A molecule with a structure with the least formal charges will be more stable than a molecule with a structure with more formal charges, and is therefore preferable.

madeleinewright

Yes, 6 would be the coordination number because the Co atom has 6 fluorines bonded to it. Only look at the atoms within the bracket when determining coordination number.

madeleinewright

The coordination number is 6 because the 3 NH3's and the 3 F's are all attached to the M, meaning the M has 6 ligands attached to it.

madeleinewright

I'm assuming that for the final, we'll only have the periodic table and list of formulas and constants that we had for previous midterms.

madeleinewright

Yes, when determining coordination number you only look at the atoms inside the brackets.

madeleinewright

Any bond that is not a single bond will have a pi bond. The second and third bonds formed between atoms are pi bonds.

madeleinewright

Since more electrons are shared in double bonds, double bonds have a stronger attraction and therefore the atoms are pulled closer together. Therefore, double bonds are shorter than single bonds.

madeleinewright

Yes, they're the same! Bent and angular are just different names for the same shape.

madeleinewright

I would generally use 1.008 amu for the atomic mass of hydrogen because it is better to be more specific and accurate, but either one should work.

madeleinewright

BeCl2 is a nonpolar molecule because it is symmetrical, and therefore the dipole moments are equal and opposite and cancel each other out.

madeleinewright

Polarizing power is the ability of a cation to distort an anion's electron. It is higher for smaller, more electronegative cations. Polarizability is how easily an anion's electron cloud is distorted. It is higher for larger, less electronegative anions.

madeleinewright

Stronger intermolecular forces between molecules will result in a higher melting/boiling point. For example, molecules with hydrogen bonding or dipole-dipole bonding will have a higher melting/boiling point than molecules with just London dispersion forces.

madeleinewright

Axial atoms lie on the vertical plane (y-axis) of the molecular structure. Equatorial atoms lie on the horizontal plane (x-axis) of the molecular structure.

madeleinewright

Ideally, atoms in a Lewis structure will all have a formal charge of 0. However, if there has to be a negative formal charge, it should be on the most electronegative atom. Lewis structures that have the fewest atoms with formal charges represent the most likely structure to occur.

madeleinewright

Chlorine is more electronegative because it is much further to the right than beryllium, whereas beryllium is only one row higher than chlorine.

madeleinewright

London dispersion forces are weak temporary forces resulting from two nearby atoms forming temporary dipoles. They occur between all molecules. Dipole-dipole interactions occur between the positively charged end of one polar molecule and the negatively charged end of another polar other molecule. Th...

madeleinewright

VSEPR stands for valence-shell electron pair repulsion model. It explains the 3D shape of molecules due to the repulsion between electron-dense regions.

madeleinewright

London dispersion forces are the strongest in molecules with larger molar masses and larger surface areas.

madeleinewright

If you had to divide 2 by 0, that would mean that the atom shares no bonds with other atoms, meaning it is not part of a molecule. Therefore, this situation would not happen when calculating formal charge.

madeleinewright

Intermolecular forces are forces between two molecules, whereas intramolecular forces are forces within a molecule.

madeleinewright

The numerals are referring to iron. When numerals are in a molecule's name, they will refer to the atom directly before them.

madeleinewright

To find the number of valence electrons for atoms that are not transition metals, you look at what group of the periodic table an atom is in.

madeleinewright

These concepts are unrelated. Ground/excited state are terms referring to the energy level of electrons in an atom. Ionic/covalent bonds are types of interactions between atoms in which they share electrons in different ways.

madeleinewright

Sometimes in covalent bonds, one atom in the bond is more electronegative than the other, so it attracts electrons more. Because of this, the electrons are shared unequally. This is similar to ionic bonds, in which one atom donates electrons and the other atom receives them.

madeleinewright

Ionic bonds are bonds where electrons are transferred from a metal to a nonmetal. This gives one atom a positive charge (the cation) and one a negative charge (the anion). Covalent bonds are bonds in which electrons are shared between atoms.

madeleinewright

The question must give uncertainty in velocity to find the uncertainty in position. The equation for Heisenberg's indeterminacy equation is ΔpΔx≥h/4π, where Δp=mΔv. If the question gives the uncertainty in velocity, you can find the uncertainty of position using Δx≥h/(4πmΔv)). However, if the questi...

madeleinewright

The De Broglie wavelength equation (λ = h/p, where p = mass x velocity) does not apply to light because it requires mass, which light does not have.

madeleinewright

The De Broglie wavelength equation (λ = h/p, where p = mass x velocity) does not apply to light because it requires mass, which light does not have.

madeleinewright

The configuration with [Ne] in the beginning is the noble gas configuration for the element. Instead of writing out the entire ground-state electron configuration, you can write the most recent noble gas for the element and then write the ground-state electron configuration for the element following...

madeleinewright

The number of orbitals depends on the subshell the orbitals are in. The s subshell has 1 orbital, the p subshell has 3 orbitals, the d subshell has 5 orbitals, and the f subshell has 7 orbitals.

madeleinewright

Electrons have mass so they will not travel at the speed of light. If you need to know the velocity of an electron to solve an equation, it will be given to you or can find it using De Broglie's equation (λ=h/(mass x velocity)).

madeleinewright

Nodal planes are regions in an electron cloud where the electron density is 0. S orbitals are shaped like a sphere, so they do not have a nodal plane. P and D orbitals have nodal planes because they have multiple lobes, and the region between these lobes has an electron density of 0.

madeleinewright

Compatible (or constructive) waves are in phase, so they line up and their amplitudes are added to each other, making a larger wave. Incompatible (or destructive) waves are out of phase, so they do not line up and their amplitudes are subtracted from each other, making a smaller wave.

madeleinewright

Definitely do the textbook problems, because some of them will be on the midterm. Also, go over the audio-visual modules and go to office hours/workshops if you have questions or want help understanding something.

madeleinewright

Professor Lavelle allows us to have an equations sheet and a periodic table during the exam, so you will be able to see the constants on this sheet.

madeleinewright

Since I'm assuming the question wants you to identify the unique location of an electron, you need to provide: n-principle quantum number; determines energy and size l- angular momentum quantum number ml- magnetic quantum number; labels different orbitals of a subshell ms- spin magnetic quantum numb...

madeleinewright

Constructive interference happens when waves are in phase, so they magnify each other. Destructive interference occurs when waves are out of phase and decrease each other, creating a smaller wave. If waves are the same size during destructive interference, they can entirely cancel each other out.

madeleinewright

Since Professor Lavelle uses 6.626x10^-34 for Planck's constant, I think that that's definitely the number you should use when working on problems. By not rounding the earlier on, you get a more accurate final calculation. Also, 6.626 is pretty far off from 6.3, so I imagine that that rounding makes...

madeleinewright

I've heard that some of the questions on the midterm are taken directly or almost directly from the textbook practice problems, so you should definitely work through those problems. I also personally like making flashcards or Quizlets and rereading through old notes so that they're fresh in my mind.

madeleinewright

The levels would not be the same for each atom, because atoms of different elements do not have the same number of protons in their nucleus.

madeleinewright

I was also wondering whether the audio visual focus topics covered the whole quantum realm section, or whether they only covered the topics we learned this week.

madeleinewright

Generally, I believe rounding is the way to go, since that is what's typically done in math.

madeleinewright

I don't think it's important at the moment, though it is important for net ionic equations. Personally, I have not found it necessary to label the state of matter of atoms and molecules to solve the questions we've been given so far.

madeleinewright

I believe Professor Lavelle only changed the units back to mL so that it would make sense in a lab setting, since generally you would not tell someone to measure out a tiny fraction of a liter, but rather that amount in milliliters. He stated in the lecture that it was not necessary to convert the f...

madeleinewright

Hi! I'm pretty sure if you go to the UCLA CCLE website and you scroll to "Media Resources" the recordings of the Friday and Monday lectures should be there. Hope this helps! That's where I've been finding the lectures! If you're taking this class online and not in-person, the lectures are...

madeleinewright

Oh wow! Very interesting to see you put Chem to action and apply it to real world stuff! I suck at cooking but maybe once I get a little further in Chem, I'll be the next Gordon Ramsey??? If you're just getting started I would recommend YouTube for some great instruction in kitchen techniques. Chan...

madeleinewright

I really like green chile enchiladas, especially because they remind me of home.

madeleinewright

If the smallest number of significant figures provided in the information given was 3, then that is how many significant figures you should use for all of your calculations, as well as your answer. You should always use the same number of significant figures as that of the value provided with the le...

madeleinewright

It only has 1 significant figure because there is no decimal point at the end. 100. would have three significant figures, as would 101.

Search found 54 matches