CHEMISTRY COMMUNITY

Megan Ngai- 3B

iron and copper

Megan Ngai- 3B

Solid phase

Megan Ngai- 3B

My TA gave me my test before thanksgiving and the final should be cumulative

Megan Ngai- 3B

Despite taking AP chem, this call has still been difficult. It covers topics more in depth than what I learnt in high school.

Megan Ngai- 3B

1 sigma and 2 pi bonds

Megan Ngai- 3B

It should be everything we’ve learnt this quarter

Megan Ngai- 3B

Cumulative!

Megan Ngai- 3B

They’re on MyUcla and my TA gave them back during my discussion before thanksgiving

Megan Ngai- 3B

The TA review sessions and reading the textbook helped a lot for me!

Megan Ngai- 3B

bent has a lone pair while linear does not

Megan Ngai- 3B

Dipole-dipole in the solid phase

Megan Ngai- 3B

^ retweet

Megan Ngai- 3B

Bent has a lone pair while linear does not.

Megan Ngai- 3B

As IMF increases in strength then the boiling point/melting point increases in order to break them

Megan Ngai- 3B

They are not the same. They both have four regions of electron density. However, tetrahedral has zero lone pairs which tribal pyramidal has one lone pair.

Megan Ngai- 3B

Electron pair geometry: number of regions of electron density
Molecular geometry: includes bonding pairs and lone pairs.

Megan Ngai- 3B

It'll be safe to memorize them all

Megan Ngai- 3B

The lone pair creates an electron electron repulsion. Therefore, it'll push the bonded atoms away from it but push them closer to each other.

Megan Ngai- 3B

Lavelle said to just know how to name them.

Megan Ngai- 3B

I just follow this chart!

Megan Ngai- 3B

It should be everything after 2D!

Megan Ngai- 3B

strongest to weakest is: covalent, ionic, hydrogen, dipole-dipole, london dispersion forces.

Bonds are stronger when they are shorter and have a higher bond order too.

Megan Ngai- 3B

It decreases across the periodic table because there are more protons so there’s a strong nuclear charge pull.

Megan Ngai- 3B

It should pick up from after 2D

Megan Ngai- 3B

Electronegativity increases up groups then across periods.

Megan Ngai- 3B

The angular momentum is the l.

Megan Ngai- 3B

Yes, everything up to 2D!

Megan Ngai- 3B

It is how strongly an atom will attract electrons. So as you go across the period increase and as you go down a group it decreases.

Megan Ngai- 3B

Whenever there is a mass given.
The equation E=hv and c=(wavelength)v would be specifically for light since c is used.

Megan Ngai- 3B

If you look up periodic table charges on Google images, it shows the charges per group (it's easy to remember). So Mg has a charge of +2 and As has a charge of -3. Therefore it would be Mg3As2.

Megan Ngai- 3B

During the midterm review session, she said we most likely don't need to memorize it but just to somewhat know visible light and gamma rays (if I remember correctly).

Megan Ngai- 3B

yes! the more electrons means a larger radii because there will essentially be more shells.

Megan Ngai- 3B

Resonance involves delocalized electrons. That means fewer repulsions and more stability with a larger volume.

Megan Ngai- 3B

The first thing is that the atoms must follow the octet rule. Distribute the electrons one by one

Megan Ngai- 3B

November 6th! As for the format it should be like the last test?

Megan Ngai- 3B

Cations are atoms lost an electron so it has a positive charge.Anions are atoms that have gained an electron so it has a negative charge.
They're important because some elements are more stable as ions because they can gain their octet by gaining or losing an electron.

Megan Ngai- 3B

Molarity is moles per liters, referring to the concentration of atoms/molecules in a solvent.

Megan Ngai- 3B

In class, Prof Lavelle ended with a = sigg. I'm pretty sure he said it was just simpler than writing greater than or equal to.

Megan Ngai- 3B

Electromagnetic radiation moves at the speed of light

Because the calc is about a type of light, c= 3x10^-8 m/s is used.

Megan Ngai- 3B

De Broglie's equation requires an object to have a mass
wavelength = h/mv

Megan Ngai- 3B

Spinning up is positive (+1/2)
Spinning down is negative -1/2

Megan Ngai- 3B

I personally read the textbook and take notes before lectures so the ideas will be explained again in different rooms. Whenever I have other questions I come to chemistry community and there are usually people who are having the same questions!

Megan Ngai- 3B

It would round up toe 64%, the next whole number

Megan Ngai- 3B

It will usually apply to when you do labs or collect data.
Accuracy is how close your data is to the true value while precision is how close your data is to each other. Your data can be precise but not accurate.

Megan Ngai- 3B

For calculating mass % I usually do four sig figs ex: 56.78%
For molar mass I would do four sig figs after the decimal points ex; 12.3456

Megan Ngai- 3B

1. you need to find the amount of moles in 5.51g.
- you divide 5.51g by the molar mass of the compound, 24.48
2. multiply by Avogadro's constant (6.022 x 10^23)
- the units of moles will cancel out and you are left with formula units!

Megan Ngai- 3B

I typically use the exact numbers that are given on the periodic table. This can prevent your answer from being a little off.

Megan Ngai- 3B

When you want to convert from moles to atoms, you multiply the molar amount by Avogadro’s number.
When you want to convert from atoms to moles, divide the atom amount by Avogadro’s number.

Megan Ngai- 3B

When trying to figure out sig figs, you should always look at the original question to figure out how many sig figs will be in your answer. In your example, there were the numbers 1.00 mol Ag atoms and the number 144 pm. Both of those numbers have 3 sig figs. The answer would not be 2 x 10^14 becaus...

Megan Ngai- 3B

For example, the problem had the numbers 3.45g and 100.79 g.

You should base the number of sig figs on the original problem. Even if you used a the atomic mass of 1.008 for hydrogen in your calculations, the sig figs should be based on 3.45g (3 sig figs) not 100.79 or 1.008.

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