CHEMISTRY COMMUNITY

Bradley Whitworth 4B

Molarity is no different for acids/bases than any other solution. It is important to understand what pH and pOH are though which is the -log base 10 of either H ion concentrations or OH ion concentrations so by raising the -pH or -pOH as a power of 10 then you can find the molarity of ions in that s...

Bradley Whitworth 4B

Yes we're looking at regions of electron density so lone pairs count so yeah that example would be 2sp2.

Bradley Whitworth 4B

Yes, the mobility should mean it's chelating.

Bradley Whitworth 4B

The ligands come before the metal.

Bradley Whitworth 4B

With respect to that specific example it doesn't matter whether you use cyano or cyanido.

Bradley Whitworth 4B

You're not wrong, solutions with a pH that's negative are known as a superacids and they are possible, just not common. If you are taking the log base 10 of a number greater than 1 you'll get a positive number hence a negative pH.

Bradley Whitworth 4B

Using the Ka value of the substance, which can be solved for if the chemical equation is known, you can also find the concentration of H+ ions and the take the -log of that.

Bradley Whitworth 4B

A chelating ligand is one who has 2+ attachments to a metal through coordination bonding.

Bradley Whitworth 4B

Regarding concentrations and the equations related to acid/base reactions I imagine we'll probably have to know those equations about Kb and Ka.

Bradley Whitworth 4B

If the molecule has lone pairs it is more than likely a lewis base because it can donate those electrons and if a molecule has a positive charge it is more likely to accept electrons therefore it is a lewis acid.

Bradley Whitworth 4B

Technically yes so I'd be precise on a test but it is a small difference so the manual might just be counting it as negligible.

Bradley Whitworth 4B

It depends on lone pairs on the central atom so draw the lewis structure and work from there.

Bradley Whitworth 4B

That's the main idea; I'd know how to count both in a molecule and know which breaks first (pi).

Bradley Whitworth 4B

When you add all the dipole moments taking into account shape you get a overall dipole moment so it is polar.

Bradley Whitworth 4B

I remember Lavelle saying the top-most d block row of elements is biologically important because he made a joke about the lower elements tending to be poisonous to life. lol

Bradley Whitworth 4B

XeF2 is nonpolar because the fluorine atoms are opposite of each other and their dipoles cancel out.

Bradley Whitworth 4B

Usually for VSEPR exact angles for everything is not expected. You should know the basic ones like 180 degrees, 120 degrees, and 109.5 degrees and you should know how lone pairs affect bonds which would be indicated by writing something like <109.5 degrees for example.

Bradley Whitworth 4B

It's really based on the VSEPR chart of shape and geometry, however the atoms will be farthest apart is how they'll arrange themselves so this determines where bond angles are formed.

Bradley Whitworth 4B

Greater impact, a lone pair would create more repulsion than just another atom.

Bradley Whitworth 4B

Yes, lone pairs create more repulsion so the angle between the 2 bonded atoms would be smaller and the two angles between the lone pair and the other two atoms would be bigger.

Bradley Whitworth 4B

Magnetic quantum number is based on l, hence m sub l is used as the variable for the magnetic quantum number. The number can be any number -l...l which is a whole number.

Bradley Whitworth 4B

If you know the frequency of light being directed towards a surface you can find the energy using E=hv (v is not actually the letter v it is a variable for frequency). Once the energy is known you can determine at what point that energy will overcome the work function of the surface at which point e...

Bradley Whitworth 4B

Moving across a period the nucleus is gaining protons so there is much more positive charge pulling on the electrons meaning the radius becomes smaller.

Bradley Whitworth 4B

The way lavelle has us writing it is in order of which electrons will ionize last to the ones that'll ionize first which basically means you write the configuration in order of the principle quantum number which for this class means you need to know that 3d^10 would be listed before 4s^2 in an elect...

Bradley Whitworth 4B

Angular momentum is l. l can be 0,1,2,3...n-1. If l=0 it tells you the s subshell is being filled, 1=p, 2=d, 3=f.

Bradley Whitworth 4B

Delocalized electrons are those that are not involved with any one specific atom or bond. In class Lavelle showed us a sort of resonance structure for benzene where instead of drawing a bunch of bonds for the ring he just drew a circle which is supposed to show that the electrons are not tied in spe...

Bradley Whitworth 4B

The point of formal charge is to make sure you are drawing the most stable and hence most likely version of a molecule you would see in nature. For example, if you draw a molecule one way and the formal charges of two atoms are 2+ and 2- they cancel out. However, if you draw the molecule another way...

Bradley Whitworth 4B

Breaking a bond always requires some energy so dissociation energy is always positive.

Bradley Whitworth 4B

It can be helpful to link what type of bond is shorter vs. longer. In other words, a triple bond is shorter than a double bond which is shorter than a single bond. We also know that a triple bond is stronger than a double bond which is stronger than a single bond. As such, you can figure that the sh...

Bradley Whitworth 4B

I doubt you'll be given a table of electronegativity values but you will most likely be given a periodic table so all you would need to know is the trend which is that electronegativity increases moving towards the top right corner.

Bradley Whitworth 4B

A simple trick is to look at the group number above each column on the periodic table. For groups 1 and 2 there are simply 1 and 2 valence electrons respectively. For groups 13-18 you only look at the last digit which is the number of valence electrons; so, group 13 would have 3 valence electrons, g...

Bradley Whitworth 4B

Formal charge is simply a comparison of the number of electrons around an atom in its neutral state to the same atom bonded in a molecule. It is important to note that calculating formal charge within a molecule does not account for electronegativity, it assumes electrons are shared evenly. It is im...

Bradley Whitworth 4B

The expression shown in class can be simplified by distributing the negative sign which helps for speed in finding formal charges. So, all it really is is taking the valence electrons of the ion you are looking at, minus the amount of electrons in lone pairs, minus the amount of electrons being shar...

Bradley Whitworth 4B

Only hydrogen. There will be cases though when maybe there are a few of the least electronegative ions that aren't hydrogen and they go in the center in different arrangements depending on how many there are. In the case of a fatty acid there are usually a bunch of carbons which in that case all go ...

Bradley Whitworth 4B

The point is that electrons are rather unpredictable to us right now so to say we know there is a double bond in one spot when it could be in another is specifying something that we don't actually know because the electrons are delocalized. So, the resonance structure is meant to account for our deg...

Bradley Whitworth 4B

The idea here is that when a trough and a trough interact as well as when a crest and a crest interact they constructively build on each other. It's the same as thinking about when you add to positive numbers together the answer gets more positive and similar when two negative numbers are added toge...

Bradley Whitworth 4B

Since t=2.0 seconds and the units given are per second you have to multiply the given value of 32 by 2 in order to get 64.

Bradley Whitworth 4B

The mass of an electron is something that is a given usually on the formula sheet with all the other constants and given equations so you should be ok.

Bradley Whitworth 4B

For velocity in that problem you just need two equations. delta p times delta x is greater than or equal to h/4pi being the first equation and delta p=m times delta v being the second equation. Knowing these are what you need you can simply plug in the information you know and solve for the change i...

Bradley Whitworth 4B

Part d is based off of the answer reached in part c, once the wavelength is known we can look at the electromagnetic spectrum and determine what type of radiation is being emitted based on the wavelength found in part c.

Bradley Whitworth 4B

For part c we need a simple equation involving the speed of light which is c=frequency times lambda. The speed of light is a constant we know, frequency was given earlier in the problem, hence we can just plug in the information we know again and carry out the algebra to solve for lambda which is th...

Bradley Whitworth 4B

For part B we need the equation which gives the energy of a photon, E=hv (note that v is not actually v it is another variable that stands for frequency). h is planck's constant which we already know, E is the energy which we are solving for, and the frequency at which an electron is drawn off the s...

Bradley Whitworth 4B

For part A we know the de broglie equation is lambda=h/mv. The question asks us to solve for wavelength, planck's constant is always the same as well as the mass of an electron, and the velocity is given in the question so the answer can be found simply by plugging in everything we know and carrying...

Bradley Whitworth 4B

The electromagnetic wave being used did not change hence the frequency did not change. By increasing the intensity you are simply increasing the number of photons being directed in the light towards the surface.

Bradley Whitworth 4B

The idea of Black Body is theoretical in that if an object truly did absorb and emit all frequencies of light it would actually be invisible. So, if you're looking to invent invisibility this is a good place to start. :)

Bradley Whitworth 4B

The purpose of the constant has to do with its units and obviously the value it has in the equation. When its units cancel out with frequency you are left with Joules, the desired unit for energy which is the purpose of the equation (to find how much energy a wave has).

Bradley Whitworth 4B

In simple terms, looking at a graph for example, two variables have a DIRECT relationship if as one increases the other also increases, the relationship between two variables is INDIRECT if as one increases the other decreases. A common example in chemistry could be the relationship between waveleng...

Bradley Whitworth 4B

All it means to be quantized is that the electrons can only have specific values for their energies; in other words, its values are discrete and not continuous. For example, its energy can only be 1,2,3,4... (again just as an example to illustrate the point) and cannot be 1.387 or 4.821 because they...

Bradley Whitworth 4B

For determining limiting reactants the key is conceptualizing what is actually happening by looking at the coefficients. When a reaction has 2 reactants with coefficients of 1 and 2 for example and let's just say a single product with a coefficient of 2 what's really happening every time we run this...

Bradley Whitworth 4B

The final volume would be the total amount added plus the original amount. If a problem says 10ml is diluted WITH 20ml that seems to imply that 20ml are being added to the original 10ml making your final volume 30ml.

Bradley Whitworth 4B

To start you would use m1v1=m2v2 to figure out m2 in this problem taking careful note that the v2 is NOT the second volume they give you because it is being ADDED to the first volume in this instance so the actual v2 would be v1 plus the amount being added. Once you find the m2 we know that molarity...

Bradley Whitworth 4B

To start you would use m1v1=m2v2 to figure out m2 in this problem taking careful note that the v2 is NOT the second volume they give you because it is being ADDED to the first volume in this instance so the actual v2 would be v1 plus the amount being added. Once you find the m2 we know that molarity...

Bradley Whitworth 4B

A theoretical yield determines the max amounts a reaction can produce because it only assumes the variables and amounts being presented in a given problem; this is similar to a physics problem about velocity or acceleration where simplified equations consider amounts in a vacuum while not taking int...

Bradley Whitworth 4B

All you need for going back and forth between moles and atoms is Avogadro's number because all a mole really is is a term for an "amount of things" so to speak. So, just like 1 dozen cookies is 12 cookies, 1 mole of atoms is 6.022x10^23 atoms. Hence, to convert from moles to atoms you mult...

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