IR and MP of Unnkown Acids_2011

IR and MP of Unnkown Acids_2011 - Quiz2NEXTWEEK...

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Quiz 2 NEXT WEEK  Includes everything from  Last quiz through today’s  lab Quiz will be in lecture
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Confirmation of  the Identity of your  Confirmation of  the Identity of your  Unknown Acid Unknown Acid Use of infrared spectroscopy and  Use of infrared spectroscopy and  melting point behavior to verify the  melting point behavior to verify the  identity of your unknown acid from  identity of your unknown acid from  last week last week
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How certain is your identification from last  week? You based your identification on measurement of two parameters, molar mass and pK a . That’s pretty substantial, but scientific confirmation is always desirable.
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What else can we do? We would like to perform some independent tests that would leave no doubt that we have identified the substance correctly. Two types of measurements that often prove useful for identification of unknown samples are the melting point and the infrared spectrum .
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Melting Behavior In a pure sample of a solid substance, all the molecules are in identical environments. They are held together in a regular three- dimensional array (a crystal) by various intermolecular forces. The stronger the forces, the more stable the crystal, and the higher its melting point . At the melting temperature, the thermal energy just equals the attractive forces that hold the crystal together.
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A Diamond Crystal In a diamond, the carbon atoms are held together by strong covalent bonds. Diamonds do not melt, even at 3500° C. Fortunately, we don’t have to determine the melting point of a diamond!
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A Portion of a Water Crystal
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Ice: A Molecular Solid In a molecular solid, the units
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This note was uploaded on 11/28/2011 for the course CHE 143 taught by Professor Raleigh during the Spring '09 term at SUNY Stony Brook.

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IR and MP of Unnkown Acids_2011 - Quiz2NEXTWEEK...

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