CHEMISTRY COMMUNITY

Eli Esagoff_1I

I don't think we have to know this specifically. But we did learn that visible light has a wavelength of 400-700nm.

Eli Esagoff_1I

I don't think so. From what we learned in class, a double bond is always one pi bond and one sigma bond.

Eli Esagoff_1I

He was explaining that both Na+ and Cl- in table salt does not change the pH of water. This does not apply to all types of salts.

Eli Esagoff_1I

I would try to avoid the naming problems on the homework.

Eli Esagoff_1I

Tetrahedral is when the central atom is surrounded by four bonding atoms. Square planar is when the central atom is surrounded by four bonded atoms and two lone pairs.

Eli Esagoff_1I

You want all formal charge to be 0 or closest to 0 when there is a charge on the molecule.

Eli Esagoff_1I

They are all the same types of bonds. The different ways that there are drawn are just for the three dimensional structure.

Eli Esagoff_1I

I don't think its any different than a normal lewis structure.

Eli Esagoff_1I

I believe the ones with lone pairs have different names for the shapes.

Eli Esagoff_1I

Could be that anions attract electrons form the cations.

Eli Esagoff_1I

I know that the shapes are still the same when you have single, double or triple bonds, but do the bond angles change when the types of bonds are different?

Eli Esagoff_1I

Yes, I think you should know the bond angles associated with each shape.

Eli Esagoff_1I

Are dispersion forces, induced dipole-induced dipole, London forces on test 3?

Eli Esagoff_1I

To reduce formal charges it is effective to move lone pairs and bonds around while continuously checking the formal charge, so it can be closest to 0. You should definitely look at formal charges in every problem that you do.

Eli Esagoff_1I

I don't think we learned this in lecture yet but I think its based on the number of bonds and what type of bonds there are.

Eli Esagoff_1I

Do we need to know how to name molecules or determine molecules based on their names for exam 3 or the final?

Eli Esagoff_1I

The formal charge for each element is:

FC = VE (valence electrons) - LPE (lone pair electrons) - 0.5BE (half the bonding electrons).

Hope this helped.

Eli Esagoff_1I

I don't think we have to know how to calculate bonds lengths in this course.

Eli Esagoff_1I

They lost electrons because it is a lot easier to lose 1-2 electrons that to gain 6-7 electrons.

Eli Esagoff_1I

If calcium loses two electrons (becoming Ca^2a) it will have the structure of Argon, having eight valence electrons.

Eli Esagoff_1I

Resonance structures are just different lewis structures. Lewis structures are the individual structures within the resonance structures. They are not two different things, they are integrated together.

Eli Esagoff_1I

Do we need to know the exceptions to the trend of electron affinity for the upcoming exam?

Eli Esagoff_1I

I don't think so. I hope not.

Eli Esagoff_1I

I think that it is due to the difference in n. n=4 is a higher energy level than n=3.

Eli Esagoff_1I

I am having trouble understanding how energy is released or spent when you add an electron to an element. Can someone please explain this to me? I understand the trend of electron affinity and how it increases towards the right (where the elements want to become stable).

Eli Esagoff_1I

Not sure, but I think for this class we just have to know that for two electrons to bond they have to spin in opposite directions.

Eli Esagoff_1I

For this question you had to use the equation: (Energy photon - threshold energy = kinetic energy). The kinetic energy is 0 so you just do (hc)/wavelength = the given threshold energy. After plugging in variable, you can sold for wavelength which equals 2.20x10^-7 m. Hope this helped.

Eli Esagoff_1I

Work function is just a synonym for threshold energy. It is not an equation, it is the minimum energy needed for an electron to be ejected from a metal. The value is usually given.

Eli Esagoff_1I

I think the questions will be similar to the examples we did in class and the questions we get for homework.

Eli Esagoff_1I

I would recommend doing as many practice as possible including using the calculator so you do not have trouble with time.

Eli Esagoff_1I

It should definitely be converted. I would recommend checking your conversion factors (you should multiply by 1,000 and divide by 3,600)!

Eli Esagoff_1I

I used them based on what information is given. You should almost always be given 2/3!

Eli Esagoff_1I

The products of combustion are always CO2 and H2O.

Eli Esagoff_1I

I like to start with the easiest coefficients and then go on from there.

Eli Esagoff_1I

The combusted element produces CO2 + H2O after reacting with oxygen.

Eli Esagoff_1I

The question gave a value that was for 1 mole of an element and he asked how we can find out the value for an individual molecule. To find this you divide by Avogadro's constant because there are 6.022 x 10^23 molecular units in a mole.

Eli Esagoff_1I

I think you should figure it out how to use sig figs as soon as possible just in case!

Eli Esagoff_1I

I'm pretty sure either way is fine. The question might specify by asking "how many meters" and then you would put: x 10^-9.

CHEMISTRY COMMUNITY

Search found 38 matches

Re: Visible or measurable light

Re: exceptions

Re: salt in water

Re: Naming on Final

Re: Tetrahedral and Square planar

Re: Lowest energy lewis structure

Re: Bond types

Re: d-block Lewis structures

Re: Naming shape

Re: Polarity

Shapes with different types of bonds

Re: Remembering Bond Angles

Topics on Test 3

Re: Reducing formal charge number

Re: How to determine molecular shape

Naming Molecules

Re: Calculating formal charges

Re: "1.20A or 1.40A"

Re: Metals

Re: Octet fule in forming compounds

Re: Lewis Structure vs Resonance Structure

Electron Affinity Exceptions

Re: Shapes of orbitals

Re: 4s and 3d

Electron Affinity

Re: What does electron spin actually mean? [ENDORSED]

Re: Test 2 #7 [ENDORSED]

Re: What is work function? [ENDORSED]

Re: test 2

Re: Test #2 [ENDORSED]

Re: DeBrogile Module

Re: Equations [ENDORSED]

Re: Balancing Chemical Equations and Combustion

Re: How to Balance [ENDORSED]

Re: Combustion Reaction [ENDORSED]

Re: Dividing by Avogadro's constant [ENDORSED]

Re: Expected mastery of Significant Figures

Re: Do we have to convert final answer to make it simpler? [ENDORSED]