chemlab - Jose A. Velilla Badui April 3, 2010 Chem 111...

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Jose A. Velilla Badui April 3, 2010 Chem 111 Final Report Group: Amy Videon Nicki Walsh Brett Veschecco TA: Annie
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Introduction: Having quality water is essential towards having a healthy life. It is said that people can survive without food for approximately a month but it is unlikely to live more than a week without water. Water not only keeps humans healthy and alive, but other living creatures also require it as well. This said it is very important that water is kept fresh and clean. In this lab we are going to be working with different types of water and will be identifying all our different procedures and experiments that were made in order to identify the “hardness” of the water. Hard water is water that contains cations with a charge of 2+ good examples of these cations are Ca 2+ and Mg 2+ (12). Even though these cations are of no threat to your health they form reactions that may leave mineral deposits that you might not want to have in your stomach, body, or home (4). Therefore distilled water is needed to fully clean the object. It is important to know that your water may contain these minerals because if it is not taken care of, it may lead to clog pipes in your home and damage things like water heaters and dishwashers. The hardness of water is usually measured in ppm (parts per million) and there are two methods that can be used in order to identify what type of water you have. These methods are known as EDTA and AA. Atomic Absorption Spectrophotometer (AA) is used to quantitatively test for the presence of elements in water. To determine what element is in a substance, a monochromatic light is emitted from a specific cathode lamp, in our case a Mg 2+ or Ca 2+ lamp, which is then absorbed by a flame that is burned from the aerosol of an unknown sample. The flame can only absorb a certain atomic electronic
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energy resulting in the remaining emitted light to be refracted into a grating that has a narrow slit allowing a specific wavelength that then passes into a photomultiplier tube (PMT), which calculates an absorbance value. With this value, the concentration of a metal can be determined with the use of a calibration curve that is determined from a solution of known concentration (12). EDTA is weak acid that we use as a titrant. In its ionized form it is able to form soluble complexes with calcium and magnesium cations. Eriochrome Black T (EBT) is the indicator that is added to the sample to form a complex with the cations. EDTA is used by adding drops to the ample forming more stable complexes with calcium and magnesium. The difference between both of the methods is that AA only gives you specific
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This note was uploaded on 04/06/2010 for the course CHEM 111 taught by Professor Keiser,josephthoheckman,kimberlyproia,michaelantsanders,rebeccalo'neill,ryanshaw during the Spring '07 term at Penn State.

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chemlab - Jose A. Velilla Badui April 3, 2010 Chem 111...

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