CHEMISTRY COMMUNITY

RubyLake1F

For 12.65 c) it says that reacting KF with water will make the water basic (release OH-). How is this true? I thought that, similar to part d) in which KBr is reacted with water, the K+ and F- would stay as ions in the water and not impact pH. Why does F- impact pH but Br- does not? Additionally, fo...

RubyLake1F

Why is it a rule that the more electronegative an atom is that is attached to hydrogen, the stronger the acid (in reference to molecules like HCl vs. H2S)? This seems counterintuitive, because a higher electronegativity difference should mean a more ionic and therefore a stronger bond.

RubyLake1F

If the equation involves an exchange of a proton (H+) and therefore involves Bronsted acids, then you should just look for the molecule on the reactants side that gives up the proton (Has one less H and charged reduced by one on the products side) as this will be the acid, and the one that receives ...

RubyLake1F

When bonds are more polar/the electronegativity difference is greater (ie. HCl) this is meant to be a stronger acid because it releases the proton more easily, however in previous units we learned that the more ionic character a bond has the stronger it is. Why is this?

RubyLake1F

How can you tell whether or not the ligand's lone pairs are close enough together to interact with the same metal? Is this something you just judge by eye based on the lewis structure/molecular geometry, or is there a rule?

RubyLake1F

I don't believe that we were taught any exceptions, so this probably wouldn't be something that would come up on an exam. However, I did just google it and I believe that there is an exception that says that if an atom has one or more lone pairs and is attached to an sp2 atom, it must be sp2. Here i...

RubyLake1F

For this type of problem you should look at the given number of bonding pairs (based on the ball and stick model of the molecule that is given), and then see if that given number of regions of electron density would explain the angles that you can see in the molecule. So for example, if you see that...

RubyLake1F

The I in ICL3 has 5 regions of electron density around it because the 3 chlorines each contribute 7 valence e-, and the I also contributes 7e- for a total of 28 e-. When you distribute electrons around the chlorines to fill their valence shells, you have only used 24 and have 4 leftover which go as ...

RubyLake1F

For 3.59 part a, the question asks for the Lewis structure of ClO. I know this will be a radical because it has 13 electrons but I put the single electron on the O so that the formal charges would be at 0. But, the solution manual has it on Cl and therefore the Cl would have a formal charge of +1 a...

RubyLake1F

Yes, and radicals will be highly reactive because they are always looking to bond with another electron so that the lone one will be paired up.

RubyLake1F

Is there a trend involved in the second ionization energy? Second ionization energies are always higher than the first ionization energy for that same element (because after removing one electron, the effective nuclear pull on the remaining electrons is stronger). In terms of comparing the second i...

RubyLake1F

I also don't understand biradicals very well, but I am pretty sure that since we did not cover this at all in class that it is not something we would need to know for the test (we would only need to know regular radicals). I think sometimes the textbook goes into a little more detail than is necessa...

RubyLake1F

Elements in the third row and below have an expanded octet because they have a 'd' sub-shell which can fit an extra 10 electrons (third row means that n=3, so 'l' can equal 0, 1, or 2 meaning that this row of the table has s, p, and d sub shells). The number of extra electrons an element can hold in...

RubyLake1F

My understanding is that if an atom in a bond is more polarizable, then its electrons are more easily distorted (shifted to one side). This means that this atom would be more likely to form a temporary dipole when bonding with another atom, because electrons shifting to one side of a bond creates a ...

RubyLake1F

If one atom in a bond is more electronegative than the other (meaning it has a stronger attractive force pulling on the electrons in the bond, and the electrons will cluster around it) then there is a dipole moment which causes partial negative charge on the more electronegative atom and partial pos...

RubyLake1F

C=8 because the only quantum number that is specified is n=2, so you know it is in the second shell which has both an s sub shell and a p sub shell. The s sub shell has one orbital, so can hold 2 e-, and the p sub shell has 3 orbitals so it can hold 6 total e-. This gives a total of 8 electrons poss...

RubyLake1F

1) Yes electrons can get excited from one sub shell to another of a higher energy level (or to a new shell)- it all depends on the energy/frequency of the light exciting the electron. 2) I believe that the radius will still increase in this case because the electron is excited to the p sub shell whi...

RubyLake1F

I think that 'penetration' to the nucleus means how close an electron can get to the nucleus. Electrons in the S sub shell have the lowest energy because they are closest to the nucleus (remembering that the closer an electron is to the nucleus the lower/more negative it's energy is) so they are bet...

RubyLake1F

Also, in terms of a wave I believe intensity is equivalent to amplitude of the wave. So if photons were just behaving as a wave then increasing the intensity would mean a larger amplitude and would increase the total energy of the light and excite more electrons. (However this does not happen becaus...

RubyLake1F

I think that this problem is somewhat trying to trick you by giving you the initial volume when it really isn't necessary. You started with 75 mL and water was added until the volume was 125 mL (which means that 50 mL was added). What matters is that in the end you have a total of 125 mL (not 125 pl...

RubyLake1F

I was also wondering if we need to know the various groups of the periodic table? I know we talked about metals vs. nonmetals vs. metalloids in class, but I don't remember discussing groups such as halogens, alkali earth metals, etc.-- however these were in the readings. Is it necessary or even help...

RubyLake1F

Do we need to know about why oxygen is an exception when it comes to ionization energy? This was a homework problem but it wasn't something that we covered in class. It also was on the practice "unicorn review" test because on question 6 d it asks you to rank ionization energies of C,N,O, ...

RubyLake1F

Why is it that b) violates ground state expectations? Isn't it somewhat random whether an electron is spinning up or down at any given moment, so it should not necessarily be true that all of the three electrons in the p orbitals have to be spinning up?

RubyLake1F

Are there any general rules about shielding that we should know? I remember the concept being discussed briefly in class but I didn't remember learning any rules about which orbitals are more effective at shielding effective nuclear charge or things like that. For example- which feels more effective...

RubyLake1F

Question 2.33 in the homework is this: Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Compare your answers to the answers to Exercise 2....

RubyLake1F

I find this to be a helpful visual: table_06.png This is a depiction of the second shell (n=2), in which there are two possible sub-shells (s and p). The s sub-shell has one orbital, which is spherical and holds a maximum of two electrons (which must have opposite spin values). The p sub-shell has 3...

RubyLake1F

If two electrons are in the same orbital they will always have opposite spins (they will be paired). If they are in two different orbitals they can have the same spin (be parallel). Electrons in the same shell, sub-shell, and orbital will never be parallel- they must have opposite spin values becaus...

RubyLake1F

The equation for the photoelectric effect is this: (Energy of incoming photon) - (energy required to eject electron from surface) = (kinetic energy of ejected electron) This makes sense because there is conservation of energy in all reactions, so whatever energy is leftover from ejecting the electro...

RubyLake1F

Actually now that I have typed out how I answered the question, I am wondering why it isn't necessary to divide the final answer by 11? The reason I am thinking you would need to divide by 11 is because there are 11 electrons per sodium atom, and you are just looking for the energy to eject one elec...

RubyLake1F

For this part of the question you actually only need to look at one of the given numbers. The "work function" is equivalent to the amount of energy required to eject an electron from a given material. It has given you the work function of sodium as equalling 150.6 kJ.mol-1, which means tha...

RubyLake1F

In question 33 you found the minimum possible energy of light that will eject an electron (ejecting the electron, but leaving it with a kinetic energy of zero), and in question 34 you are given the wavelength of the actual photons of light hitting the source (implying that there is extra leftover en...

RubyLake1F

Today in class he went into more detail on this and said that when an electron travels down energy levels to n=1 (the lowest energy level, making that large jump/drop in energy from n=2 to n=1) it is in the Lyman series. This electron will have a large energy transition and will therefore release a ...

RubyLake1F

I also had this question. I don't know the answer for sure, but I am guessing that we should definitely know experiments such as the photoelectric effect that we cover heavily in class, simply because understanding how a certain property of light was discovered will help us in knowing when and how t...

RubyLake1F

A photon is light, which has a particular wavelength, frequency, energy, and other values (I believe).

So I think if you are talking about the energy of a photon it would be in Joules, wavelength would be in meters, frequency would be in Hz (s^-1), etc.

RubyLake1F

For example, electrons can only exist at certain energy levels. So electrons jump up from n=1 to n=2, or down from n=4 to n=3, absorbing or releasing photons (energy packets) with discrete energy values. They could never exist between energy levels (i.e. at n=1.34) and therefore there are only certa...

RubyLake1F

The attached image is helpful in visualizing the relationship between 'c', wavelength, and frequency. The bottom parts of the pyramid 'wavelength' and 'frequency' multiply to equal the top value 'speed of light', and the top value can divide by either bottom value to get the other bottom value maxre...

RubyLake1F

For any problem involving the value of 'c', does this factor into how many sig figs we give in our answer? Sometimes in class we write 3x10^8 instead of 3.00x10^8, but in general should we assume we know the speed of light to three sig figs for all calculations?

RubyLake1F

Yeah I would say always use the maximum number of digits given to you in the question or periodic table on the assessment, and then round according to significant figures only at the very end of the problem.

RubyLake1F

Each separate/distinct cluster of shapes is a molecule, so use the key to count up the number of each type of shape (type of atoms) that make up each molecule. Then count the number of each type of molecule and use it to write the equation for the reaction. So for example in the box on the left (the...

RubyLake1F

For the first test, are we expected to know particular common compounds? A lot of the assigned problems in the book expected us to know the formulas for compounds such as ammonia and nitric acid. These are familiar to me from seeing them in high school chemistry but I definitely don't have a bunch m...

RubyLake1F

It is also helpful to always start with the element that is found the in the least number of compounds on each side of the equation. If an element is found in multiple compounds on each side (i.e. commonly seen elements like hydrogen and oxygen) it is likely that if you balance these first and then ...

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