Chemistry 100 Significant Figures. Rules for Significant Figures Zeros used to locate decimal...
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Transcript of Chemistry 100 Significant Figures. Rules for Significant Figures Zeros used to locate decimal...
Chemistry 100Significant Figures
Rules for Significant Figures
Zeros used to locate decimal points are NOT significant. e.g., 0.5 kg = 5. X 102 g 1 sig. fig.
What if the measurement was 500 g?
5 x 102 g 1 sig. fig. 5.0 x 102 g 2 sig. figs. 5.00 x 102 g 3 sig. figs.
Certain values are exact (e.g., from definitions) 1 kg = 1000.00000……… g exactly 1 s = 1000.0000 …………. ms exactly 1 cal = 4.18400000 ……… J exactly.
Addition and Subtraction Operations.
Results from +, - operations should be reported to the same number of decimal places as that of the least precise term. 12.37+ 10.7 = 23.07 (calculator)
12.37 2 places after the decimal. 10.7 1 place after the decimal.
Final answer must have only 1 place after the decimal = 23.1
Multiplication and Division Operations
Results from x, operations should be rounded off to the same number of significant figures possessed by the least precise term. 0.80 x 217.81 = 174.248 0.80 2 sig. figs. 217.81 5 sig. figs. Final answer can only possess 2 sig.
figs. = 1.7 x 102
Carrying digits through a long calculation
Example:129 / 13.76 + 10.1 = 9.375 + 10.1 =
19.475 = 19.5 Usually carry an extra digit through
the calculations, then round off the final answer according to the significant figure rules.