sigfig - measurements to determine the precision of the...

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Determine significant figures (SF) in measurements Example (cm) SF a) All non zero digits are significant 1286 12.86 b) Numbers with zeroes: Zeroes to the left of the first non zero digit are not significant 0.0025 .025 025 Zeroes between non zero digits are significant 40.23 4023 Zeroes to the right of the non zero digits: a) In quantities with a decimal point are significant 4.000 42000. 0.000040 b) In quantities without a decimal point 42000 we do not know unless specified. 100 In this class, if the trailing zeroes are significant 4300 they should be expressed in exponential notation. Exponential notation 4.2 x 10 4 The coefficient indicates the number of SF. 4.20 x 10 4 4.200 x 10 4 4.2000 x 10 4 Numbers obtained by counting and definitions are exact numbers Example SF 25 dollars. 205 birds 12 inches = 1 foot 60 min. = 1 h. When measurements are computed consider the widest possible range of uncertainty of the
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Unformatted text preview: measurements to determine the precision of the result. The following is a shortcut that can be used when exact results are not crucial. Multiplication and division, count the number of significant figures . The result is expressed with the same number of digits as the least precise of the measurements. e.g. The density of a compound with a mass of 12.4 g (three SF) and a volume of 13 mL (two SF): = 12.4 g/ 13 ml = 0.95 g/ml (two SF) b) Addition and subtraction, the result contains the same precision as the least precise measurement: e.g. the result of adding the masses obtained in balances with different precision: 9.9 g + 10.128 g + 10.1305 g = 30.2 g (tenths of a gram). Round off the each of the following numbers to three SF: 2.23456 223456 2.23600 223600 2.23556 223556 2.24556 224556 Note: 5 rounds to the nearest even number 1.75 2SF rounds 1.8 and 1.25 rounds to 1.2...
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This note was uploaded on 03/06/2012 for the course CHEM 14A 142042200 taught by Professor Lavelle during the Summer '10 term at UCLA.

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