Quantum Numbers

Today in class we learned about quantum numbers. Every set of quantum numbers contains four numbers that represent different values.

• The first quantum number is the value of the principal energy level, labeled as n

• The second quantum number is the number that determines the type of sublevel, labeled as l

• The third quantum number runs from -1 to +1, labeled as ml

• The fourth, and last, quantum number is spin of the electrons, labeled as ms

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/quantum.html

Helpful Links for Studying

Here are some links I found helpful for studying for the quiz:

http://www.valley-city.k12.nd.us/jrsrhigh/jrsrstaff/jrsrstffpgs/mn/Chemistry/Chapter4/Wksht41.pdf

http://scienceprimer.com/electromagnetic-spectrum-calculation-practice-problems

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/electronconfigpractice.html

http://www.schooltube.com/video/ab18287622e84f3d91db/Determining%20the%20number%20of%20valence%20electrons%20from%20your%20periodic%20table%20and%20electron%20configuration

Spec lab

Today in class we conducted the spec 20 lab using a spectrophotometer. To start out the spectrophotometer was zeroed out using a cuvette with just water in it and adjusting the % transmittance. Once it was zeroed out we placed a cuvette with Cr(NO3)3 in the spectrophotometer and recorded the % transmittance and absorbance. Next we placed a cuvette with CoCl2 and recorded its % transmittance and absorbance as well. We repeated this for many different wavelengths for both solutions.

Flame Test Lab

Today in class we performed the flame test lab. With this lab we put sticks soaked in different metallic solutions, as well as one solid metal, into the flame of a bunsen burner. By burning these different metals we were able to see a color change within the flame. By recording these colors we were able to determine the wavelengths of the metals including an unknown. In order to determine the unknown metal we had to calculate the energy of one mole per photon of all the metals and compare the numbers. In doing so, my lab partner and I were able to determine our unknown (D) as sodium.

This picture is a little blurry, but you can see the drastic change in color of the flame

Looking at the flame through cobalt glass for metals that turned the flame orange

Wavelength Calculations

Today in class we learned how to calculate wavelength, frequency, and energy.

The formula for wavelength is  λ = c/f



The formula for frequency is f = c/λ




The formula for energy is E= hf

Molar Mass of an Unknown Acid

Today my lab partner and I finished our Molar Mass of an Unknown Acid lab. This lab was another titration, however, it was different from the last one in that we didn't know what the acid was in the second titration. Using KHP to standardize, we were able to calculate the molar mass of the unknown acid. After performing the titrations of the KHP and the unknown acid, we then calculated the molar mass of KHP. Once the average molarity was found, we were able to convert it to moles of the unknown acid using the volume of NaOH used, the average molarity of KHP, and the mole to mole ratio. With the moles of the unknown acid we were able to use it as the divider of the mass of the unknown. In dividing the mass by the moles, we were able to calculate the molar mass as 164.76 g/mol.

The unknown acid at its equivalence point

This link helped with the calculations for this lab

Percent Acetic 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