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Unformatted text preview: of the coefficient and exponent separately, we get:
9.0 × 1 0 –16 = 3.0 × 10 –8 Significant Figures. Measurements, and calculations based on measurements, must be reported so as to
convey information about the number of meaningful digits. The significant figures are those digits in a
measured number that include all certain digits plus one having uncertainty. If we measure the length of a desk
top with a meterstick calibrated in millimeters and find the length to be 972.5 mm, then the digits 9, 7, and 2
mean there are 9 hundreds, 7 tens, and 2 ones, and because of the calibrations, these digits are certain. Fivetenths, however, is an estimate because it falls between the finest calibrations. Someone else might read it as
0.6 or 0.4. The result could be expressed with error limits as 972.5 ± 0.1 mm. This measurement provides three
certain digits and one uncertain digit. All of these provide useful information, and we say the number 972.5 has
four significant figures.
Always take care that the numbers you write reflect the proper number of meaningful digits. The process of...
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This note was uploaded on 09/15/2009 for the course CHEM 102 taught by Professor Bastos during the Spring '08 term at Adelphi.
 Spring '08
 BASTOS
 pH

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