Buret uncertainty

If you use a 50-mL buret, design your titration to require 20-40 ml of reagent to produce a small relative uncertainty of 0.1-0.05%. 

Absolute uncertainty expresses the margin of uncertainty associated with a measurement. If the estimated uncertainty in reading a calibrated buret is 0.02 mL, we say that 0.02 mL is the absolute uncertainty associated with the reading. 

Relative uncertainty compares the size of the absolute uncertainty with the size of its associated measurement. The relative uncertainty of a buret reading of 12.35 0.02 mL is a dimensionless quotient ... 

The volume delivered by a buret is the difference between final and initial readings. If the uncertainty in each reading is 0.02 mL, what is the uncertainty in the volume delivered ... 

The precision of reading a 50-mL buret is about 0.02 mL. Since a buret is always read twice, the total absolute uncertainty may be as much as 0.04 mL. The relative uncertainty will vary inversely with the total volume delivered. It becomes apparent that a titration with a 50-mL buret should involve about 40 mL... 

The mean of the molarity of the sodium hydroxide is 0.1165 M, and its standard deviation is 0.0002 M. Similarly,.two buret readings (initial and final) are required to obtain the volume of base delivered, and the total uncertainty is... 

When making a measurement, it is important to record the results to the appropriate number of significant figures. For example, if a certain buret can be read to 0.01 mL, you should record a reading of twenty-five milliliters as 25.00 mL, not 25 mL. This way at some later time when you are using your results to do calculations, the uncertainty in the measurement will be known to you. 

Buret. Burets are long, narrow, finely graduated tubes as shown in FIGURE B.l. They are designed to deliver precise and variable volumes of liquids into other containers. A stopcock or pinch clamp at the base of the buret provides for release of volumes between about 0.05 mL and the total volume of the buret. Burets are especially useful for adding solutions stepwise in small increments. Burets typically have uncertainties of about... 

Commonly, relative uncertainty is expressed in parts per thousand (ppt) a value given by multiplying the result of the above equation by 1000. In the example of the volume of 36.27 mL delivered by a buret as discussed above, the relative uncertainty in parts per thousand is... 

If the buret had been used to deliver only 1.52 mL, the absolute uncertainty would still be 0.01 mL, but the relative imcertainty would be the following ... 

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