CHEMISTRY COMMUNITY

LilianKhosravi_1H

when something is referred to as "less acidic" it's usually talking about the pH of something rather than the actual strength of the acid but a weak acid would cause little change in pH of a solution or make something acidic. An acid is strong when the pKA is lower and is weaker when the p...

LilianKhosravi_1H

I think it has to do more with the number of bonds. So a single bond is a sigma bond, a double is a sigma and pi bond, and a triple is one sigma and two pi bonds.

LilianKhosravi_1H

H2O is a monodentate because even though it has two lone pairs, only one of those will bind and the other one won't because it has no way of biding to the central atom since it's on the oxygen with the other lone pair that is already bound. Basically, the positions of the lone pairs won't allow it t...

LilianKhosravi_1H

Vivian Gonzalez 1A wrote:What do we need to know about pi and sigma bonds for the final?

I would say know what they each represent and also how many of each make up a single, double, and triple bond.

LilianKhosravi_1H

what we did in discussion was create an equilibria where we used the amphoteric compound with water and tried to see if we could use it as both an acid and a base. The example we did was H2PO3- : using it as an acid = H2PO3- + H2O ⇌ (HPO3)2- + H3O+ using it as a base = H2PO3- + H2O ⇌ H3PO3 + OH- so,...

LilianKhosravi_1H

I think that's because in Bio we talked about how covalent bonds can't be broken in water but ionic bonds can.

LilianKhosravi_1H

you could either memorize the VSEPR formulas and their shapes or you could draw the lewis structure and figure out the shape based on its number of bonds and lone pairs.

LilianKhosravi_1H

You would know the molecule is bent if it has any lone pairs. In the case of water, although it has two bonds that are connected to the H, it also has two lone pairs which push down on the two bonds and make a "bent" shape rather than it being linear.

LilianKhosravi_1H

I don't think so, I think a double bond is always 1 sigma and 1 pi bond

LilianKhosravi_1H

Formal charge is the charge assigned to an atom in a molecule which is why when the molecule has no charge, the formal charges of the individual atoms must equal zero when added up.

LilianKhosravi_1H

that's a good question, I also thought we always use formal charge in a scenario like this

LilianKhosravi_1H

yeah that's right!

LilianKhosravi_1H

you would probably have to check the formal charges and see which position for the double bonds creates fewer formal charges

LilianKhosravi_1H

The question asks which M3+ ions (where M is a metal) are predicted to have the following ground-state electron configurations:
a.) [Ar]3d6
b.) [Ar]3d5
The solutions manual says a is Co3+ and b is Fe3+ but could someone explain how they got this answer?
Thanks!

LilianKhosravi_1H

I think it's because a half full and full orbital are more stable than partially filled d orbital so the electron from 4s goes to 3d.

LilianKhosravi_1H

Ionization energy is the energy needed to remove an electron from an atom. The trend for ionization energy is that it decreases down a group and increases across a period. So it's harder to remove an electron of an atom that has octet e- (8 valence electrons) because it's fully occupied (stable) and...

LilianKhosravi_1H

To figure out the valence electrons of an elements just count across the periodic tables from the left to the right starting with one and ending with eight. So all the elements in group 1 have one valence electron like H, Li, and Na. N has 5 valence electrons because when you start counting from Li,...

LilianKhosravi_1H

Yeah I had the same question but I think it just means number of atoms.

LilianKhosravi_1H

When d is occupied by electrons then it becomes lower in energy than s which is when you would put it before s. So elements with 21 electrons or more would have the d come before the s because this is when we first see d become occupied by electrons.

LilianKhosravi_1H

I was wondering the same thing cause on some of the days my classes conflict with the review sessions planned

LilianKhosravi_1H

for part A you're supposed to find the wavelength of the ejected electron so you would use the De Broglie formula which is wavelength = h/m * V and sub in the numbers (6.626 x 10^-34 J*s)/(9.11x10^-31 kg)(3.6 x 10^6 m/s) which gets you 2.02 x 10^-10 m or 202 pm. h is a constant and so is the mass of...

LilianKhosravi_1H

yes the mass is a constant and is on the cover page of the tests so you don't have to worry about memorizing it.

LilianKhosravi_1H

The one on my cover of test 1 is -(hR/n^2), which is the same as the one given in lecture.

LilianKhosravi_1H

proper unit for frequency is Hertz (Hz) which is cycles per second (s^-1) and for wavelength it's usually m (or nm) but it depends on the question because it can ask for the wavelength in a particular unit.

LilianKhosravi_1H

3.37 x 10^-19 J is the answer to part (a) of the problem, it's the energy of an excited sodium atom when it generates a photon. It's then used to figure out the energy of the 5.00 mg of sodium atoms and 1 mole of sodium emitting light at the given wavelength for part (b) and (c).

LilianKhosravi_1H

So today in lecture we talked about how when the electron goes from n=4 to n=2 the change in energy would be negative and so in return the energy of the photon emitted is positive so in return the frequency is positive. But, if the electron goes from n=2 to n=4 then the change in energy will be posi...

LilianKhosravi_1H

The amplitude of a wave is its height, but I also remember Dr. Lavelle saying how as the amplitude increases then the energy or intensity of the wave also increases. He compared it to a wave at the beach saying that a taller wave will be more powerful than a shorter wave.

LilianKhosravi_1H

I was wondering the same thing, I thought they might be typos?

LilianKhosravi_1H

For this question you don't need to know the final volume since you are given the final mole which is 0.0045 mol C6H12O6 so you can set up your equation as 0.728 M (M=mol x L^-1) x V = 0.0045 mol and to get the initial volume you would divide both sides by 0.728 mol x L^-1 which equals 6.18 x 10^-3 L.

LilianKhosravi_1H

I think it's personal preference, as long as we've gone over the material then you should be fine.

LilianKhosravi_1H

I can't remember exactly what Dr. Lavelle said in class, but one cycle per second is a 1 Hertz which equals the frequency. So if there are 2 cycles in one second then the frequency is 2 hertz.

LilianKhosravi_1H

I think as long as you are given three of those things from the formula then you can use it. You might even be given the mole rather than M or V which you can substitute in place of MiVi since n(moles)=MV

CHEMISTRY COMMUNITY

Search found 32 matches

Re: Strength of Acid and Bases

Re: Sigma vs Pi Bonds

Re: Homework Problem 17.33.)

Re: pi bond and sigma bond

Re: Identifying an amphoteric compound

Re: Ionic Bonds vs Covalent Bonds

Re: Naming Structures

Re: How To Know When A Molecule Will Be Bent?

Re: Double bond with 2 pi bonds?

Re: Formal Charge Meaning

Re: Radical HW 3.59

Re: hwk problem 3.37

Re: Where to put double bonds? [ENDORSED]

Question 3.11

Re: Exceptions [ENDORSED]

Re: Octets and ionization energy

Re: Ammonium Sulfate Example in Notes

Re: formula units [ENDORSED]

Re: Switching 3d and 4s

Re: Review Sessions [ENDORSED]

Re: 1.33 using De Broglie

Re: Calculating kinetic energy of an emitted electron [ENDORSED]

Re: Rydberg Formula for Atomic Hydrogen [ENDORSED]

Re: units for frequency and wavelength [ENDORSED]

Re: HW Question 1.25

Frequency if energy goes from n=2 to n=4

Re: wavelength description [ENDORSED]

Re: M.2 Example in Textbook

Re: G.11 / Volumes for Solutions

Re: Homework? [ENDORSED]

Re: Frequency vs Cycle

Re: Molarity formula