Lab for Grade 10 Chem Percentage Yield

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Preparation of Standard Solutions and Use of a Spectrophotometer to Measure the Concentration of an Unknown Solution

Introduction
Concentration is the ratio of the quantity of solute to the quantity of the solvent or the quantity of solution. By knowing this, CO(NO3)2 *6H2O
Purpose
What is the percent transmittance of six different solutions of cobalt (II) nitrate hexahydrate using a spectrophotometer? Materials
* Graduated cylinder (10 mL)
* Graduated cylinder (25 mL)
* pipet
* 1 cuvette
* Safety goggles
* Electronic balance, accurate to two decimal places
* Test tube rack
* 5 test tubes
* Volumetric flask (100 mL)
* Beaker (100 mL)
* Spectrophotometer
* Distilled water
* Squirt bottle

Procedure
See page attached.

Observations
Original Molarity| Dilution| New Molarity| Percent Transmitted| 0.160| | 0.160| 18|
0.160| 12 mL to 16 mL| 0.12| 26|
0.160| 8 mL to 16 mL| 0.8| 40|
0.160| 4 mL to 16 mL| 0.4| 58|
0.160| 2 mL to 16 mL| 0.2| 80|
Unknown| | | 56|

Conclusion
By using a spectrophotometer with the unknown solution, a percent transmittance of 56 appeared. The concentration of the unknown solution was then easily plotted on a graph to show the corresponding data. Error Analysis

-One of the 6 solutions of CO(NO3)2 could not have been rinsed out of the cuvette properly. -The test tubes could have not been washed properly, affecting the percent transmittance. -Liquid could have spilled on the cuvette before inserting it into the spectrophotometer, therefore affecting the final data. -Some light could have entered the spectrophotometer due to improper closure.
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