Ch2 - Quantitative Chemical Analysis Chapter 2: Tools of...

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Quantitative Chemical Analysis Quantitative Chemical Analysis Chapter 2: Tools of the Trade Tools of the Trade
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2 Safety is always first priority Wear them or leave the lab
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3
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4 Analytical Balances Gravimetric measurements Gravimetric analysis
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5 Originally, operated by balancing on a knife edge (fulcrum)
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6 Now they operate using an electromagnet and integrated circuitry Block diagram illustrates operation of the electronic balance. The pan position detector raises or lowers the number which in turn changes the current through the coil. When the pan is returned to the null position, the number is related to the weight on the pan. This is an example of a digital null measurement.
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7 Precision – sensitivity of instrument ability to reproduce the same reading scatter of measured values signal-to-noise-ratio (S/N) Accuracy – how close to the “real” value the measurement is
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8
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9 Using the Analytical Balance condensation don’t breathe on the object to be weighed drafts keep the case doors closed
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This note was uploaded on 03/28/2011 for the course CHEM 300L at USC.

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Ch2 - Quantitative Chemical Analysis Chapter 2: Tools of...

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