The main idea of stoichiometry this week was to understand how to use conversions to figure out a problem containing different units. We have done two worksheets on stoichiometry to further understand and master the concept. For example,
How many grams of gold would be produced from 551g of gold (III) oxide in the reaction 2Au2O3 --> 4Au + 3O2? (molar mass of gold (III) oxide is 441.93 g/mol)
The main idea is to multiply the given value by different forms of 1 in order to get the same results in a different unit. For example, in the equation above, the numerator and the denominator all equal each other (1 mol Au2O3 = 441.93g Au2O3). That way, we can change the units of the given number without changing the actual value (anything multiplied by one will equal itself).
Lab Report - Blue #1 Dye
This week, we performed a lab with Blue #1 Dye and different kinds of sports drinks. The question to guide our lab was "What is the Relationship Between the Concentration of a Solution and the Amount of Transmitted Light Through the Solution?" and "How many grams of Blue #1 Dye is there in 500mL of Powerade and Gatorade?".
As we collected data, we found that the absorbance and concentration of Blue #1 Dye had a direct linear relationship. This was related by the equation y=0.1385x-0.0078 (x=absorbance and y=concentration).
The activity that really tied everything that we learned this week was to find the mass (g) of 500mL of Powerade and Gatorade. We applied our knowledge of stoichiometry to our lab to see how much dye was in our drinks (the equation and process are all in the lab notebook). We found out that there is approximately 1.98x10-4g of Blue 1 Dye in Powerade, while in Gatorade, there were 5.15x10-5 g.
In addition to the lab, we worked on post lab questions. These questions tested us if we knew our material well. The first question asks us how to find concentration given the concentration and volume of the diluted solution. Here, we used the equation M1V1=M2V2to find the concentration in uM.
Here is the work:
The concentration of the original stock turns out to be 17.5uM.
Main Ideas
The main ideas this week were to become comfortable with stoichiometry, how labs work in the class, how to use our lab notebooks, and how stoichiometry can be applied in labs.
I'm still uncomfortable using stoichiometry to convert units. I wasn't sure where to start when we white-boarded our problems for the mass of Blue #1 dye. I feel that I participated well by knowing how to use the colorimeters properly and doing the prelab activities before the lab, however I don't think I understood stoichiometry as well as I should have. My ideas have changed about converting units. I had thought they were very easy to do, however after learning stoichiometry, I understood that there were more steps in the conversion than what I had imagined.
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