Quantum Numbers

Each element in every atom is assigned a set of four quantum numbers and no two electrons can have the same quantum numbers.
1. The first number is the principle quantum number which is the principle energy level.
2. The second number is the angular momentum quantum number which is the sublevel but the sublevels are assigned number. 0 is s, 1 is p, 2 is d, and 3 is f.
3. The third number is the magnetic quantum number which is determined by how much of the orbitals are filled
4. The fourth number is the quantum spin number which is either +1/2 if its the first electron in an orbital or -1/2 if its the second.
This link has practice problems with the answers so you can check if you get it right.

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Spec 20

We used a spectrophotometer in lab today. We found percent transmittance and absorbency of cobalt and chromium by placing a cuvette into the machine and setting a certain wavelength. Here's my data from the lab.

Cr Ion
Wavelength (nm)	% T	Absorbance
375	59.2	0.226
400	49.4	0.306
405	49.2	0.309
415	50.2	0.300
425	54.4	0.264
440	62.6	0.203
455	72.8	0.138
470	80.2	0.096
490	81.2	0.091
500	80.4	0.094
520	72.6	0.139
530	68.2	0.167
540	63.8	0.196
550	60.4	0.219
570	56.8	0.245
580	57.0	0.245
600	62.4	0.205
625	72.6	0.138

Co Ion
Wavelength (nm)	% T	Absorbance
375	98.8	0.006
400	92.4	0.035
405	90.0	0.047
415	86.4	0.063
425	80.4	0.094
440	66.0	0.180
455	49.6	0.305
470	40.2	0.396
490	32.2	0.492
500	30.4	0.518
520	31.6	0.500
530	38.0	0.422
540	47.8	0.320
550	58.6	0.232
570	78.6	0.104
580	85.4	0.069
600	90.2	0.045
625	92.2	0.036

And some pictures

Electron Configuration

The electron configuration of an atom is where the electrons are found and how many there are in an atom. There are four levels to describe the location of an electron in an atom: principle energy level, sublevel, orbitals, and spin. The principle energy level describes how far away from the nucleus an electron can be found. Its symbol is n. There are four different sublevels, s, p, d, and f. The first principle energy level only has one sublevel, the 1s sublevel. The second principle energy level has two sublevels, 2s and 2p. The third principle energy level has three sublevels, 3s, 3p, and 3d. The fourth and all subsequent principal energy levels have four sublevels, 4s, 4p, 4d, and 4f. Each sublevel ahs a specific number of orbitals, the s sublevel has one orbital that can hold 2 electrons, shaped like a sphere, the p sublevel has 3 orbitals that can hold 6 electrons, shaped like dumb-bells orientated perpendicular to each other around the x, y, and z axis, the d sublevel has 5 orbitals that can hold 10 electrons, and the f sublevel has 7 orbitals and can hold 14 electrons, both the d and f sublevels have complex shapes. Each electron is paired with another and they have opposite spins. 

When writing the electron configuration of an element the first number is the principle energy level then the sublevel then the number of electrons is the superscript. This link gives you practice writing the electron configuration for different elements.

Flame Test

This lab was really neat. We did this lab to help us understand how wavelength corresponds to color. In the lab we burned a few chemicals and recorded the color we saw then using the color we looked up the wavelength. 

Energy, Wavelength,and Frequency Calculations

All waves have wavelength, amplitude and frequency. If a wave has a short wavelength and a high amplitude it has high energy, but if a wave has a long wavelength and a low amplitude it has low energy. To find the speed of a wave you multiply wavelength and frequency together. Electromagnetic radiation moves through a vacuum at a speed of 3.00*10^8 m/s, so that is what we use for speed of a wave. You can also find how much energy is in a photon with a certain frequency. To do this you multiply the frequency by Planck's constant which is 6.63*10^-34 J*s.

 

This link gives you practice problems on how to find energy, wavelength and frequency, and it shows you how to do it if you get stuck.

Titrations Lab

We ran a lab this week similar to the one before, but this time to find the molar mass of an unknown acid. For this lab, we titrate an acid we are given to as I said before, find the molarity of it. First to start the lab, we had to standardize the base solution, so I weighed about 0.2g, added it to a Erlenmeyer flask by rinsing it with diluted water, added about 100mL of diluted water, added 2 drops of indicator, and  finally titrated it until it turned pink. We did this twice and averaged the two for our calculations. When the solution turns pink, we know that all of the KHP had been reacted. Next, we did the same thing by titrating the unknown acid that we had to weigh. Finding the molarity in the first two and solving for just the moles of HA is what was then used for more calculations. 
Here are some pictures from the lab:

Blame isn't really being assigned to anyone, but my lab partner and I (mostly her) broke and erlenmeyer flask. #chemfails :/

Percent Acid in Vinegar Lab

Over the last few days my lab partner and I have performed the Percent Acetic Acid in Vinegar lab. By standardizing a solution of NaOH with the acid potassium hydrogen phthalate, or KHP, in a titration we were able to determine the molarity of the NaOH solution. Using this standard NaOH solution, we were also able to determine the percent of acetic acid, HC2H3O2 in commercial vinegar.



Adding distilled water to the Erlenmeyer flask in order to dilute the vinegar



After adding two drops of the indicator phenolphthalein we were able to titrate the solution


After all of the titrations were complete, the calculations for the percent acetic acid in vinegar could be made by calculating the average molarity of NaOH and plugging that in to find the molarity of the acetic acid. The molarity could then be multiplied by the molar mass in order to find the mass of solute in the solution. With this mass the percent acetic acid in vinegar can be determined by dividing it by the volume of the solution.

This was helpful in calculating the percent acetic acid in vinegar

Titrations

Today's lecture in chemistry was over titrations and equivalence points. A titration is a technique that is used in order to determine the concentration of an unknown acid or base. During the titration, a neutralization reaction, or a reaction that uses equal quantities of acid and base, occurs. A neutralization reaction is reached once the amount of acid and base, with respect to concentrations, are equal and this can be seen when the solution in the Erlenmeyer flask turns a light pink. This change in color is caused by an indicator that is pH sensitive which changes the color once the reaction is complete. An equivalency point in a titration is when the moles that were originally in the solution are equal to the moles after the titration.

A titration is shown in this picture above. the base is in the buret, being kept there by the stopcock. The Erlenmeyer flask contains the acid which has an unknown concentration, this flask is placed right under the buret. The stopcock is then opened in order to allow the base to go into the acid until the color change occurs.
I found this site helpful in order to practice some titration calculations

ICE Box

We learned ICE box problems. These types of problems are designated solely for when you identify the acid or base is weak, but still want to find the pH of it. You cannot use the same system as you would for the strong acids and bases, but instead use this. To set up the problem you first write the letters ICE vertically along the left hand side. The I stands for initial, the C stands for change and the E stands for equilibrium, and the chemical equation is above the box, horizontally. Next to the I is always the molarity given to you in the problem, and going across will be two dashes, since no data will be shown there. Next, in the C column, you will place a -x. +x, +x, and finally in the E column you will add the two columns up. Then, this information will be put into the equation Ka= [H+][ClO-]/[HClO]. This will further turn into a quadratic equation when numbers are plugged in, and you must solve for x. An easy way to do this is to graph the quadratic and identify the zeros with a function on the calculator. The final step is to convert into pH with the equation pH=-log[H+]. 
Here is a picture and some links to visually understand and practice this concept:
http://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/ICEchart.htm
https://www.youtube.com/watch?v=tT-2xk9ZG_A