CHEMISTRY COMMUNITY

haryn Shin 1H

Hi, is hybridization(sp, sp3, etc.) always and only related to the number of bonds the compound form? Or are there any exceptions to this?

haryn Shin 1H

Hi, for the molecular geometry of seesaw, there are 4 bonded atoms to the central atom and a lone pair (looks like a literal seesaw). Hope this helps!

haryn Shin 1H

Yes, bent and angular are the same thing or the same molecular geometry in VSEPR theory. The bond angle for bent/angular is slightly less than 120 (<120).

haryn Shin 1H

Hi! Ideally, having the smallest formal charge on the atoms of the lewis structure would give the most stable structure to the compound. "Minimizing formal charge" is used in that context and we would want the formal charge to be close to 0 as possible.

haryn Shin 1H

Hi, for the conjugate base, you would simply remove the H+ and adjust the charge accordingly by adding a -1 charge. For conjugate acid, you would do the opposite. You would add an H+ and thus remove the -1 charge. Hope this helps.

haryn Shin 1H

I believe you would need to know all types of the molecular geometry (like tetrahedral, linear, bent, etc) and their corresponding bond angles ( for example, linear is 180 and angular/bent is slightly less than 120). Hope this helps!

haryn Shin 1H

Hi! A delocalized pi bond is when the electrons are free to move over more than two nuclei. It means that it is not associated with a single atom or a covalent bond. Hope this helps.

haryn Shin 1H

According to VSEPR, the molecular geometry of H20 is Angular or bent, because the central atom O has lone pairs. Hope this helps!

haryn Shin 1H

You are correct in that NH3 is a neutral species, thus have a charge of 0 and Cl has a charge of -1.
But we have Cl2 outside of the bracket, which we need to take into account as well--> we need to add 2(-1).
Therefore, the oxidation number is +3.

haryn Shin 1H

If the coordination number is #4, I believe you just need to know that there are two possible structures, tetrahedral and the square planar. Hope this helps!

haryn Shin 1H

[Co(NH3)4Cl2]Cl

Here, we will be looking at the oxidation number of Cobalt.
NH3 is a neutral compound, thus its charge is 0.
And not that Cl has the charge of -1.
Thus,
x + 4(0) + 2(-1) + (-1) = 0
x -3 = 0
and x =3.

The oxidation number for this compound is there fore +3.

haryn Shin 1H

For the see-saw molecular geometry, the bond angles are slightly less than 90 degrees and slightly less than 120 degrees (<90, <120).

haryn Shin 1H

The bond angle of the molecular geometry of a linear shape would be 180. It looks something like: X---A---X.

haryn Shin 1H

The most favorable resonance structure would be the one with the least formal charge in the central atom. Usually, the most favorable resonance structure has a formal charge of 0 in the central atom. Hope this helps!

haryn Shin 1H

First, you have to figure out the molecular formula of the compound. You do this by dividing each given mass (the percentage x 100 assuming that the sample mass is 100g) by the molar mass to get the moles and go about on figuring out the molar mass after getting the ratio of each compound. Then, you...

haryn Shin 1H

Hi! A delocalized pi bond is when the electrons are free to move over more than two nuclei. It means that it is not associated with a single atom or a covalent bond.

haryn Shin 1H

The formal charge on the central atom doesn't need to be 0 all the time, but the formal charge of 0 is the most stable structure, so you would want to draw a lewis structure with the formal charge as close to 0 as possible.

haryn Shin 1H

Yes, I think we should be familiar with all the shapes/ molecular geometry for the upcoming midterm and you can find them in the textbook. Hope this helps!

haryn Shin 1H

Yes, the bond angles are derived from the molecular geometry of the molecules. I believe we have to be at least familiar with the different molecular shapes and their corresponding bond angles. Hope this helps.

haryn Shin 1H

Hi! How do we determine if a molecule is polar or nonpolar? This is an example problem from the textbook: 2E.27 Predict whether each of the following molecules is likely to be polar or nonpolar: (a)C5H5N (pyridine, a molecule like benzene except that one --CH-- group is replaced by a nitrogen atom);...

haryn Shin 1H

Hi! The question is: Draw the Lewis structure and give the approximate bond angles of (d) N2H4. The answer gave us the lewis structure drawn with all single bonds and a lone pair on each Nitrogen atom, but I drew it by connecting the two nitrogen atoms with a triple bond. Why can't we draw it with a...

haryn Shin 1H

Hi!
I was wondering why in the electron configuration of chromium, the number of unpaired electrons 6, not 4.
Isn't it [Ar] 4s23d4?

haryn Shin 1H

Hi, would we need to memorize all the molecular shapes and their corresponding bond angles for the upcoming midterm?

haryn Shin 1H

Considering the trends in the periodic table, the electron affinity, and thus the electronegativity is lower towards the bottom of the periodic table, which results in greater difference in electronegativity for BaBr2 than BeBr2. Greater difference in electronegativity means that the compound is mor...

haryn Shin 1H

Hi, to determine whether a compound is covalent or ionic, we usually look at the difference in electronegativity values. If the electronegativity difference is greater then 2, it is an ionic bond whereas the electronegativity difference less than 1.5 corresponds to a covalent bond. Hope this helps!

haryn Shin 1H

Hi, would we be given the electronegativity values when we have to calculate the difference in the values to determine which compound is more ionic/ covalent?

haryn Shin 1H

I'm a little confused about the concept of a compound having ionic character / covalent character. Can someone explain this please? Thank you:)

haryn Shin 1H

Hi, The question is: Draw the Lewis structure of each of the following reactive species, all of which are found to contribute to the destruction of the ozone layer: (a) chlorine monoxide, ClO The book only gave the answer of a lewis structure with a single bond, but I drew a lewis structure with a d...

haryn Shin 1H

Hi! The Octet rule applies to most atoms including both the central atom and the surrounding atoms, though there are exceptions to the octet rule such as a compound with unpaired e-, and more. Hope this helps!

haryn Shin 1H

Hi! The amplitude and the energy are in the directly proportional relationship, meaning that if for example, the amplitude increases, the energy also increases, and when the amplitude decreases, the energy correspondingly decreases as well. Hope this helps!

haryn Shin 1H

Hi! On the periodic table, the electron affinity, similar to ionization energy, increases across a period and decreases down a group! Hope this helps!

haryn Shin 1H

If you are given the radius, you should multiply by 2 to get the diameter and compute with the diameter. Hope this helps!

haryn Shin 1H

By definition, the formal charge is the charge assigned to an atom in a molecule and after calculating the formal charge, we apply it to the lewis structure by simply putting the formal charge next to the element. Hope this helps!

haryn Shin 1H

The number of electrons in an elements is equivalent to the number of photons, so it is basically the atomic number on the periodic table. Hope this helps!

haryn Shin 1H

Yes, when we're dealing with photons, we just use the equation wavelength = c/v, and with mass, electrons, and momentum, we use the de broglie formula wavelength = h/p. Hope this helps!

haryn Shin 1H

You multiplay the whole equation with the denominator in order to get whole numbers in the equation. Hope this helps!

haryn Shin 1H

We normally say that a wavelength less than 10^-15 is usually not detectable. Hope this helps!

haryn Shin 1H

Yes, threshold energy and the work function mean the same thing when calculating with the equation.

haryn Shin 1H

The two rydberg's constant is basically equivalent to each other, but they are just measured in different units. R= 2.178 x 10^-18 J is in Joules (J), which is consistent with when we're calculating energy for example, while R= 3.29 x 10^15 Hz is measured in the unit of Hertz or s^-1, and is typical...

haryn Shin 1H

Basically, constructive interference is when the wave's trough overlap with another trough or the one crest overlap with another, making the wave build up and have a higher amplitude than the previous one. Destructive interference is when the waves cancel out and it result in lower to no amplitude.

haryn Shin 1H

The delta just means change in something so delta E in this case is the change in energy, which would be E (final) - E(initial). If you're just calculating the energy at the moment, you would just use E=hv.

haryn Shin 1H

Question #11: A red line is observed at 656.3 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line.
n1=?
n2=?

How did you guys approach this question?

haryn Shin 1H

Hi! Can you explain how to approach this question from weeks 2,3,4 homework problem 5:
How many photons with a wavelength of 833 nm are needed to melt 437 g of ice? The enthalpy of fusion of water can be found in this table.

haryn Shin 1H

Hi!
When photons hit the metal surface, the electrons in the metal absorb some of the photon's energy. And the energy required to remove an electron, or the threshold energy, is called the work function, ϕ.
ϕ=hf

haryn Shin 1H

Can somebody explain when to use λ= c/f and when to use the De Broglie equation λ=h/(mv) ?

haryn Shin 1H

Hi!
1J = 1kg x m^2 x s^-2
mass is in kg so the kg cancels out,
velocity is in m/s, and planck's constant (h) is in J.s
so the units cancels out and we're left with m, the unit for wavelength.

haryn Shin 1H

Mass of an electron is given as 9.11 x 10^-31 in Lavelle's equation sheet. Hope this helps!

haryn Shin 1H

9.11 x 10^31 is the mass of the electron and it is given, so you most likely don't have to solve for it.

haryn Shin 1H

This is so inspiring! Thank you for putting the effort to post this:)

haryn Shin 1H

Yes, c will be the speed of light which is 3.00 x 10^8m/s, and it's a constant meaning the value of c will never change. Hope this helps!

haryn Shin 1H

Thank you so much for the advice!!:)

haryn Shin 1H

Accuracy is a measurement's closeness to the true value, while Precision tells us how close to one another the measurements are.

haryn Shin 1H

Hi! I need help with question #10 of week 1 homework. I just don't know how to approach the question. [Consider the nucleophilic addition reaction of 2‑butanone with excess propyl magnesiumbromide, made in situ by reacting 1‑bromopropane with metallic magnesium, to make 3‑methyl‑3‑hexanol...] Thank ...

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