CHEMISTRY COMMUNITY

April Pazos 3D

How can I rearrange the rydberg equation freq=rydberg eq(1/n1^2−1/n2^2) to get what value N2 is ?

April Pazos 3D

How do we solve for the number of spectral lines?

April Pazos 3D

Calculate the wavelength, in nanometers, of the spectral line produced when an electron in a hydrogen atom undergoes the transition from the energy level n=4 to the level n=1.

I keep getting 85.68. What other equations can I use to solve this problem?

April Pazos 3D

Particle like means it is quantized. When thinking of wavelike properties, I suggest going through the experiment with the slits. This experiment showed wavelike properties because the constructive interference that occured. Thus, whenever there is diffraction, that is a sign of a wavelike property

April Pazos 3D

To get the most accurate answer, use Lavelle's.

April Pazos 3D

How many photons with a wavelength of 701 nm are needed to melt 467 g of ice?
i used the enthalpy of 333.6 J/g
turned nm to m
my answer is 5.82x10^23 but achieve says it is wrong.

How do I fix my calculator if that is the problem?

April Pazos 3D

A liquid is exposed to infrared radiation with a wavelength of 7.37×10−4 cm. Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 57.42 J of heat? HELP!! I keep getting 2.02x10^21 and it says that I am wrong. What am i doing wrong? U...

April Pazos 3D

The intensity of the light is important to distinguish whether electrons will be ejected (dependent on frequency) or if more electrons will be ejected (once we are at the threshold).

April Pazos 3D

Hi! The photoelectric experiment debunked the idea that light had the properties of a wave. Since increasing the intensity did not result in electrons being ejected but increasing frequency did, the light was no longer looked at as a wave, rather than a particle that interacts at a 1:1 ratio with el...

April Pazos 3D

Hi! Joules= kg x m^2/ s^2. Planck's constant has the units of Joules x s for reference.

April Pazos 3D

Why do we have to relate these two equations in order to get a wavelength for the question professor Lavelle showed in today's lecture?

April Pazos 3D

Discrete means that the values are only allowed to be whole number integers.

April Pazos 3D

Are the supplemental homework in the week 1 tab being graded for completion as well or is that not being graded?

April Pazos 3D

How do we know these reactants and products have a 1:1 ratio?

April Pazos 3D

How many sig figs does 7.000 have?

April Pazos 3D

Always use the balanced equation to get the most accurate yield.

April Pazos 3D

The textbook can be found on chrome and firefox instantly. However, if you wish to use it on safari, please go to your settings and un enable blockers for ccle.ucla.edu.

April Pazos 3D

Yes, in order to eliminate the fraction, multiply by the whole number it is divided by to have only whole numbers as stochiometric coefficients.

April Pazos 3D

Yes, if they are asking you to find the molecular formula as well, it is necessary to provide you the molar mass for the said compound. Because the equation is the molar mass of compound/molar mass of empirical formula, we need the molar mass of the molecular formula.

April Pazos 3D

Were the surveys due last Friday or tomorrow?

April Pazos 3D

What are some examples of polydentate ligands besides EDTA ? How can you tell from the formula if it is a polydentate ligand?

April Pazos 3D

pKa and pKb is the measure of the strength of the acid or base. pH is the measure of the concentration of h+ protons.

April Pazos 3D

Resonance is the delocalization of electrons. Thus, if you have a structure with resonance, delocalization is occurring.

April Pazos 3D

What do we need to know about myoglobin and hemoglobin for the final exam?

April Pazos 3D

When calculating the frequency of energy absorbed or emitted from changing levels of energy, which equations will be used in the problem?

April Pazos 3D

How can you tell how many hydrogen bonding sites there are?

April Pazos 3D

The difference in electronegativities dictates the size of the dipole moment.

April Pazos 3D

Unhybridized orbital because electron repulsion causes too much energy cost for an electron.

April Pazos 3D

If the complex is negatively charged, -ate is added to the TM.

April Pazos 3D

A promotion occurs during hybridization when an atom needs to form a certain amount of bonds. For instance, carbon needs to bond 4 times. During hybiridzation we promote on electron in order to occupy space in an extra orbital.

April Pazos 3D

Since it has a negative charge, cobalt would turn to -ate.

April Pazos 3D

If the dipoles in the molecule do not cancel out, then the molecule will be polar.

April Pazos 3D

Transplatin is not a chemotherapy drug because it cannot form a coordination compound with the DNA. Since it has its Cls on opposite sides, it cannot align with the DNA and bond.

April Pazos 3D

Cisplatin stops cell division because they have their Cls on the same side of cisplatin. When cisplatin is administered, the Nitrogens along the guanine will displace the Cls on the Cisplatin which causes the bond to be blocked when it is being replicated.

April Pazos 3D

London forces is dependent on the size of the molecule. Thus, just look for the larger molar mass.

April Pazos 3D

How does an atom having preference affect the molecular shape ? Dr. Lavelle brought up several times how Fluorine will change the dynamic since it has preference.

April Pazos 3D

It would be helpful to be familiar with all names not just the most common.

April Pazos 3D

Dr. Lavelle said as long as you draw one structure of the resonance molecule then you should be fine. We are looking at the molecular geometry of one resonance structure. Since a resonance structure is a blend of all structures, their molecular geometries should be the same across all resonance stru...

April Pazos 3D

When trying to find out if a molecule is polar or non-polar, write all the dipole moments and see if they cancel out. If the dipole moments do not cancel out, then the molecule is polar. If the dipole moments do cancel out, then the molecule is non-polar. Since SF4 has 4 bonds and one lone pair, the...

April Pazos 3D

When you add two electrons to the element sulfur, the ground state configuration leads you to Ar. The fact that Ar happens to be a noble gas is why the answer was abbreviated.

April Pazos 3D

Why would C4H9OH have a higher melting point than C2H5OC2H5?

April Pazos 3D

Polarizability depends on size and charge. No assumptions can be made since each element has a different amount of electrons. The more electrons the farther they are away which allows the nucleus to not have a strong hold on them. Thus, the more electrons the easier it is to have a dipole moment bec...

April Pazos 3D

Yes, electronegativity is how much an atom can attract electrons. A dipole moment is when one atom is strongly attracting the electrons more than the other. Thus, the dipole moment is centered from electronegativity.

April Pazos 3D

As an atom increases, they have more electrons which causes more electron repulsion.

April Pazos 3D

Lone pairs count as electron densities.

April Pazos 3D

The question will specify if it wants it or not.

April Pazos 3D

Will hybridization be on the midterm ?

April Pazos 3D

Isoelectronic means atoms and ions with the same number of electrons.

April Pazos 3D

The purpose of calculating formal charge is to allow you to check if your lewis structure has the lowest energy possible. The least amount of formal charges you have the better.

April Pazos 3D

Yes. Since all the elements in that column have the same number of valance electrons they will follow the same exception.

April Pazos 3D

Drawing lewis structures is really just trial and error. If you draw a full lewis structure and realize you have too many electrons surrounding the elements, then a double bond has to be used. If you still have too many electrons after you have done a double bond, then a triple bond needs to be used.

April Pazos 3D

Removing the second electron will always be more difficult than the first because once one electron is removed it makes the net charge positive. Once the net charge is positive, the element will hold on to it's electrons more tightly which in turns means it is harder to remove a second.

April Pazos 3D

Resonance is more stable since it has the ability to have different arrangement of electrons. Resonance allows multiple bond characters which lowers the energy of the arrangement of atoms.

April Pazos 3D

How do we determine the amount of valance electrons the D-block elements have ?

April Pazos 3D

How would I represent an anion in a lewis structure?

April Pazos 3D

What are Pi bonds? How do they contribute to a lewis structure?

April Pazos 3D

Delocalized means that the electrons are not associated with one atom. Instead they can move around.

April Pazos 3D

The significance of this example was resonance because we are visually seeing how different arrangements of electrons can be written in several ways. The importance of bond length in this example is that the average of the atom is a hybrid.

April Pazos 3D

Resonance is determined when a lewis structure has multiple bonds in different locations that are the same as each other.

April Pazos 3D

What is the importance of the photons and electrons untangling and what effect does it have on Heisenberg's Indeterminacy Equation?

April Pazos 3D

The periodic table Prof. Lavelle provided is good.

April Pazos 3D

In problems, how do we know when to use these two concepts?

April Pazos 3D

Why are Cr and Cu considered exceptions?

April Pazos 3D

I use khan academy as another resource when I feel like I did not grasp the concept fully. It provides extra support and practice problems !

April Pazos 3D

Always balance the elements that stand alone VS. balancing the elements that have several others attached to them. For example, Li3N (s) + H2 (g) -> LiNH2 (s) + LiH (s) I would only work with balancing H2 and LiH. Li3N (s) + 2H2 (g) -> LiNH2 (s) + 2LiH (s).

April Pazos 3D

Doing the problem is up to you and what your preference is. The process is still the same whether you rearrange it immediately or not.

April Pazos 3D

The Paschen and Brackett series use lower energy, and they are on the lower scale of infrared region.

April Pazos 3D

When light is emitted, an electron goes from high orbit to low orbit and the electron is absorbed when going from low orbit to high orbit. The difference of energy between two orbitals determines the energy and frequency of light emitted. Thus, different frequencies equate to different wavelengths, ...

April Pazos 3D

What is the unit for 1 angstrom?

April Pazos 3D

Whether you are adding, subtracting, multiplying, or dividing, the ground rule is to have the same amount of sig figs as the value with the lowest amount of sig figs.

April Pazos 3D

I begin by balancing the element that shows up the least then I move on to the next. The posts above sum up the process pretty well though!

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